Glenn Burns weather
What El Nino will bring us this winter
El Nino continues to develop in the equatorial Pacific Ocean this month. We continue to see significant warming of the sea surface temperatures. It is likely to be a weak El Nino even for the late fall and winter. That being said, it is still likely to disrupt and change the global wind patterns. So what does that mean for Georgia and the Southeast?
If it behaves like a typical El Nino, our winter is likely to the colder than normal. The Climate Prediction Center is giving north Georgia a 33 percent chance of below average temperatures from December through February. Precipitation however, is a little more uncertain. During a weak or moderate El Nino, central and south Georgia tends to receive much more rain than north Georgia.
Here in north Georgia, we can be divided even further. The mountains would receive less precipitation than counties to the south. There appears to be much uncertainty about this. To that end, the Climate Prediction Center has placed the area north of Macon in the “Equal Chance” category, meaning we have too many variables to make an accurate prediction. In my 30 years of seeing the effects of El Nino, which occurs about every three to five years, I have seen winters where it has been drier than normal and wetter than normal with nearly identical situations.
Above average winter precipitation during an El Nino is highly dependent on the position of the southern branch of the jet stream. It will travel from the Pacific Ocean, through California, the southern states, and into Georgia. It could waver only 50 miles north or south and completely change our weather. It is definitely a fine line of variability.
While we all wait for winter weather, I must remind you November is a “transition month.” As we transition from autumn to winter, we can and often do, face devastating severe storms, like we did last month. Six tornadoes touched down on October 14th. Insured losses were more than $6 million.
The tornadoes were spawned along the leading edge of a squall line called a QLCS (quasi-linear convective system). They are extremely difficult to detect on radar. We did spot them and we did track them and because of the technology we have, no one was hurt. That is and always will be our goal. I would expect to see several more systems like the October outbreak this month, especially with the changing southern branch of the jet stream over us.
So, with that in mind, take a little time to enjoy the remaining fall color. The holiday season is upon us and winter is looming. November is a month of transition so get ready for stronger cold fronts, stronger storms ahead of those cold fronts, and the freezing temperatures that will no doubt follow.
Glenn Burns is chief meteorologist for WSB-TV in Atlanta.
October 2014 column
Remembering the hurricane that hit Atlanta
At the beginning of the month, we were looking at the long-range models for this October. The patterns are showing a warmer than average month with about equal chances of above or below average rainfall. As we were pondering the rainfall, one of our meteorologists reminded me of the night of October 4th and 5th, 1995.
I remember that night all too well. Category 4 Hurricane Opal was spinning in the Gulf of Mexico. Although satellite observations showed some weakening, it was still a very formidable tropical cyclone. What bothered me the most was its fast forward speed. Opal was moving at nearly 30 miles per hour and aiming for the Florida Panhandle, heading almost due north.
When tropical systems move inland they are usually moving about 5-10 miles per hour. As they move over land they no longer have the energy from the ocean to maintain their strength. That is the way things are supposed to work. This was not the case with Opal. The hurricane was maintaining its heading and speed. It would only take eight hours at that speed to move from the panhandle into the Atlanta metro area. This would not be enough time for the storm to substantially weaken. It was going to be a very long night.
I watched the eye move inland and make a bee line up the Georgia-Alabama state line. Squalls in the outer bands were already producing torrents of heavy rain and spinning up many tornadoes. When Opal moved into the western part of the metro area, we clocked winds at 79 miles per hour. Opal was still a hurricane!
As the outer bands continued to swirl, warnings for winds and tornadoes were coming in fast and furiously. Damage reports flooded our newsroom. Thousands of trees were down. Power was out for many. At the height of the storm, nearly 400,000 people had no power. However, Opal was not quite finished. Winds on the ground are slowed by friction. The higher up in the storm, the stronger the winds. When those winds hit the north Georgia Mountains, it was mayhem. Thousands upon thousands of trees, some more than 100 years old, snapped like twigs. It wasn’t until Opal reached Tennessee that it was downgraded to a tropical storm. When it was all said and done, 43 counties in Georgia were under a state of emergency. There were several deaths from tornadoes and fallen trees. All totaled, there was $5.1 billion in damage in the Southeast. It was one of the scariest nights I have ever had forecasting the weather.
When our fall cold fronts move south of Georgia they will tend to stall in the Gulf of Mexico during the month of October. So far, the giant Sahara dust cloud has kept the Atlantic quiet. I hope never to see another storm like Opal. Rest assured we will be watching the Gulf intently this month. Aside from possible tropical development this month, October is my favorite month of the year. I hope the blue sky, low humidity, cool morning lows and warm daytime highs will prevail. Expect the fall color to peak around the third week of the month and continue through early November.
September 2014 column
A strange summer comes to close this month
Summer ends this month. Fall officially begins on September 22 at 10:29 p.m. I have to say, this has been one of the strangest summers I have ever seen. It seemed to be a season of extremes. Rainfall was certainly not a problem. We had pop-up afternoon storms somewhere in Georgia just about every day. The storms this summer produced some of the most intense lightning we have seen in Severe Weather Center 2. Trees would get struck and would crash onto houses. People in their living rooms were hit. There were numerous attic fires from lightning every time a storm popped up.
On the other end of the spectrum were the temperatures. This summer our temperatures were below average by 2-3 degrees. There were several major cold fronts that moved through in July and August. When we track a summer cold front, we usually just see a shift in the wind from the south to the northwest. The northwest wind will tend to bring in some slightly drier air. However, the cold fronts this summer were actually cold fronts. We set low temperature records on several occasions in July! 59 degrees in Atlanta was the coolest low temperature record. Many mountain communities saw low temperatures in the upper 40s in July. I have never observed that in my 32 years here at WSB.
It is about this time of year when I begin to receive inquiries about our winter weather. As we all remember, last winter was brutally cold and we had two major winter weather events. Winter patterns don’t usually set up until late October or November. However, if I were to make a prediction now, I would make that prediction on persistence. What I saw last winter, to some extent, actually continued into the summer. I am not seeing a major pattern change as we head into September. That being said, I would think our upcoming winter might be another cold one. I cannot comment on whether or not there will be any snow or ice, as they are random events.
Temperatures this month should still be warm with plenty of time to enjoy more time on the lake. If you are out on the lake on the night of September 8th, you’ll be in store for a real treat. The full Harvest moon will rise in the east at around 9:30 pm. It is a little early this year.
I hope you’ve enjoyed your summer. Seasons are changing this month and I will be here, as always, to get you through the transition. Enjoy!
August 2014 column
An explanation of 'dog days'
All last winter, all I heard was how cold it was. Everyone was wishing for an early summer. Guess what’s happening now? You got it! Everyone is now asking when it is going to cool down! I can assure you, it won’t be in the month of August. We are in the Dog Days of Summer.
I have heard many north Georgia residents say it is the time of year that drives dogs mad because it is so hot and miserable. This is NOT the case. You might have heard of a constellation named Orion. Often referred to as “The Hunter,” Orion is a prominent constellation visible throughout the world. Nearby is the constellation Canis Major, which is Latin for “greater dog.” According to constellation lore, Canis Major is one of Orion’s hunting dogs.
Located in Canis Major is a star named Sirius, also called the “Dog Star.” With the exception of our sun, Sirius is the brightest star visible from Earth. The brilliant, blue-white star’s name comes from the Greek word for “searing” because Sirius is so bright. It was easy to track even for early astronomers. During April and early May, Sirius was visible in the southwest after sunset. But by the time mid-summer would come along, Sirius would rise and fall with the sun and get lost in the daytime light.
However, the ancients knew that the “Dog Star” was still there, up in the sky with the sun during the hottest time of the year. They reasoned that since Sirius was so bright and up there with the sun, it must be adding to the heat to produce the hottest time of the year. Of course we all know Sirius is still there, it just does not produce any heat. So that is the true story of how the Dog Days got its name.
While we all simmer through the Dog Days, we have a real treat coming this month. If you happened to miss the Super Moon in July, don’t worry. The best is yet to come! The August Super Moon will be the closest the moon comes to earth all year, and should be the best of the five Super Moons of 2014 as it passes within 221,765 miles of us. The next Super Moon is on August 10th. September 9th is the last Super moon. The “Super Moon” is a relatively new term to refer to the “perigee full moon” or new moon, basically, when the moon comes to the closest point in its orbit to earth. (The moon’s orbit is an ellipse, not circular) “Super Moon” usually refers to any of a number of times the moon orbits earth that fall within the closest 10 percent of orbits. I don’t think there is anything quite as beautiful as a full moon rising over Lake Lanier on a warm, Dog Days of Summer night. Enjoy!
July 2014 column
When sunglasses fog up, it's one of those days
It is early morning and the sun has been up for about an hour. When you walk out the door to get into your car, your sunglasses immediately fog up. You know it’s going to be one of those days you wish you could hang out by the pool. It’s already stiflingly hot.
Far above the ground, where you see the jets flying, it is very cold. As the sun continues to bake the ground, the air over the ground begins to heat up, becoming lighter and very buoyant. A column of warm, sticky, tropical air begins to rise. With the air around this column being very cold, it begins to rise faster and faster until the water vapor in the air condenses to form a cloud. Our cloud stops rising as it encounters a layer of warm air. Overnight, the heat we absorbed all day escapes and rises. It forms what we call a “cap.” Our little cumulus cloud tries to climb higher but there is no longer any cold air around it to help push it upward. By early afternoon a weakness forms in the cap and the air rushes upward at tremendous velocity. The cloud continues to grow with huge towering branches of cumulus clouds. Trillions of water droplets begin to get super-cooled, remaining liquid below 32 degrees. Some water droplets begin to freeze into small hailstones.
Gravity begins tugging at the hail pulling it toward the ground. On their way, they collide with the super-cooled water droplets and grow larger. But the updrafts coming from the ground are relentless. They bring the hailstones back up, high into the cloud, coalescing into even larger and larger hailstones. The rain and the hail begin to collide in the stronger upper level winds. And then it begins with the first crack of lightning.
A summer storm is born and it’s a big one. In the middle of this storm the updraft of warm and humid air continues to supply the storm with energy. It continues to grow larger. Looking down from space, our satellite imagery shows what looks like a large cotton ball, towering over surrounding clouds. Our radar shows a large core of hail and very heavy rainfall. As we switch modes on the radar to show wind velocities, we can see straight-line winds on the edge of the thunderstorm at 60 mph. We are also detecting hail the size of quarters. The National Weather Service radar operator issues a Severe Thunderstorm Warning. Our storm is now reaching its mature stage. All hell is breaking loose on the ground. Rain, hail, high winds and severe lightning, as many as 100 strikes in 10 minutes are occurring.
As the rain and hail continue to fall, the air below the storm begins to cool. The updraft of hot humid air that was once feeding the storm with energy is being overwhelmed by the rain and hail-cooled air. It is scrounging for energy but there is none. When the storm can no longer continue there is a last downward rush of cold air. The air rushes toward the ground at nearly 80 miles per hour. As it hits the ground it fans out in all directions, causing roof shingles to peel away, lawn furniture is scattered everywhere and several trees are blown down in this wet microburst. From the time the storm first formed to its last death throws, 45 minutes have passed! This was a typical “pulse type” thunderstorm frequently found during the month of July. This is why you need to pay particular attention to the weather forecasts and have a weather app or weather alert radio when you want to spend a day on the lake.
Be safe this July my friends. Summer storms can be deadly.
June 2014 column
Summer could bring interesting weather
At 6:51 a.m. on Saturday June 21st, summer officially begins. Summer 2014, from what I have seen, could be a very interesting summer.
If you will recall, last summer was absolutely miserable. We had showers and thunderstorms pretty much every single day and consequently, cooler than average temperatures. While the above average rainfall was certainly great at keeping the lake level up, it was not so great for those of us wanting to enjoy the lake. So, the question of the day is, are we going to see a re-peat performance.
Hurricane season begins June 1st and continues to the last day of November. During June, the most likely area for tropical development is in the Gulf of Mexico. By July, the favored area is the Caribbean, and in August and September, that area shifts to the Atlantic, where the major hurricanes are likely to form.
Since 1970, according to the U.S. Geological Survey, there has been an increase in the amount of Sahara dust streaming across the Atlantic Ocean. Last hurricane season, the dust clouds were especially thick as storms in Africa tossed the dust high into the atmosphere. We saw it as high as 15,000 feet! Sahara dust clouds have a chilling effect on the ocean, preventing the formation of the tropical waves that push off the west coast of Africa. Normally, these waves will evolve into tropical depressions or tropical storms. However the Sahara dust clouds prevent incoming sunlight for warming the ocean to the levels that would support tropical system formation. Hurricane experts believe that will happen again this season so a much fewer number of systems will likely develop.
Another reason this tropical season will be below average has to do with what is happening on the other side of the world, in the equatorial Pacific Ocean. It appears we may have a very strong El Nino developing, the likes of which we have not seen since 1997. El Nino is a warming of the sea surface temperatures in the Pacific that will result in a changing of the jet stream and wind patterns across the globe. The effects of El Nino in the winter months for north Georgia are more pronounced, with cooler temps and above average precipitation. However, in the summer months, it will also have a major impact.
Scientists studying El Nino development believe we just might have a cooler than average temperatures this summer as a result. Last summer, because of the rain, we only had a handful of days where temperatures reached 90 degrees. It may be the same this summer because the jet stream will be at a much lower latitude, supplying us will little shots of cooler air. Will we see above average rainfall? It will all depend on how quickly El Nino forms. I can say from past experience, summer storms will likely be stronger because of the increased wind shear.
My summer forecast then, will be for cooler than average temperatures. I cannot definitively say much about increased rainfall yet. We will be watching as things continue to evolve.
May 2014 column
Last month was quiet on the storm front
April was an incredibly quiet severe weather month across the country. The number of tornadoes was 46 percent of normal. Here in Georgia, we average four tornadoes statewide in April. We only had one tornado and it actually occurred from a heavy shower and not a thunderstorm. There were several minor injuries and damage to two homes just to the northwest of Griffin in Spalding County.
In the month of May, the average number of tornadoes in Georgia is three. This is based on the past 30 years of weather records. From what I have seen in the long-range models, rainfall in May should be below our 3.67 inch average. Maybe the below average severe storm season will continue. Beyond that, the Climate Prediction Center is giving us equal chances of above or below average rainfall. That prediction was made before signs of a developing El Niño.
It appears that an El Niño is in the works right now and it might be a big one. El Niño can boost the odds of extreme weather (droughts, typhoons, heat waves) across much of the planet. If current forecasts stay on track, El Niño might end up being the biggest global weather story of 2014. The most commonly accepted definition of an El Niño is a warming of the tropical Pacific Ocean south of Hawaii, lasting for at least five consecutive three-month “seasons.” A recent reversal in the direction of the Pacific trade winds appears to have kicked off a warming trend during the last month or two. That was enough to prompt U.S. government forecasters to issue an El Niño watch last month.
Forecasters are increasingly confident in a particularly big El Niño this time around because, deep below the Pacific Ocean’s surface, off-the-charts warm water is lurking. Currently there is a huge sub-surface wave of very warm water that currently spans the tropical Pacific Ocean – big enough to cover the United States 300 feet deep. That’s a lot of warm water. As that blob of warm water moves eastward, propelled by the trade winds, it’s also getting closer to the ocean’s surface. Once that happens, it will begin to interact with the atmosphere, boosting temperatures and changing weather patterns.
In the United States, this could bring welcome rains to our western states suffering from severe drought. While residents there might be very happy about this, these rains may be so heavy as to cause more flooding and mudslides. In Georgia, we may see a benefit. In fact, this may be good news for eastern coastal states. An El Nino will create strong easterly winds across the Atlantic. With so much wind shear, Atlantic hurricanes will have a VERY tough time developing. Colorado State University hurricane forecasters, including Dr. Bill Gray, is prediction only three hurricanes to form this season, one of which will be a major hurricane. Certainly good news!
April 2014 column
Spring is like a split personality
April is a month I like to call a Jekyll and Hyde month. For the most part, the weather this month is mostly tranquil and serene. In fact, it is the driest month of the year in north Georgia. We have abundant sunshine, the plants and trees are still in bloom, and temperatures continue to warm. However, things can frequently turn ugly in a heartbeat.
I remember back in 1987 when temperatures were warming and we were on a fast track to warmer spring weather. Then I noticed this huge area of cold arctic high pressure barreling out of Canada. At the same time, there was a stalled out cold front in the Gulf of Mexico. A low pressure area was forming along the front. It looked like a typical winter storm scenario. As new computer model data continued to stream in, it was now apparent the moisture and the cold were about to meet up at the same time, and right over Georgia. Even though we were well into the 70s, I had to make a prediction. Within 48 hours, we had 4-6 inches of snow from the mountains in to the northern suburbs of Atlanta. Two days later, we were back in the 70s! The latest I believe it ever snowed in our area was April 25 when 1.5 inches fell in 1910, also the heaviest for the month, and the latest-ever freeze.
While April can be very pleasant, and on rare occasions even snowy, it is a month that has spawned violent weather. The Dunwoody Tornado was a significant tornado that tore across the northern suburbs of metro Atlanta on April 9, 1998. It struck parts of the four most populous counties in Georgia: Cobb, Fulton, DeKalb, and Gwinnett. The most severe damage was in the Dunwoody area, where the storm reached a high-end F2 on the Fujita scale, making it one of the strongest and most damaging recorded to have hit that area.
The thunderstorm was part of a major outbreak that started in the south-central United States on April 6. The particular supercell which produced it also spawned the tornado that ripped through western suburbs of Birmingham just a few hours prior, on the evening of April 8. That storm was rated F5 and killed 32 people.
March is usually the time we see the most severe storm activity and tornadoes. However, the abnormally cool air we had, severe storms never materialized. I don’t believe I have ever seen a March go by without a single severe storm. I am hoping severe storm season just isn’t getting a late start. We shall see in the Jekyll and Hyde month of April. Be prepared.
March 2014 column
Residents need to take warnings seriously
February 2014 may go down as one of the most bizarre weather months I have ever seen. After “Snowpocolypse” in late January, an even stronger winter storm developed in the Gulf of Mexico and ran right into a wedge of cold arctic air. It was amazing to see the different types of precipitation we endured over that 36-hour period.
We were a lot more prepared for the second one. Our 1-2 inch snowfall on January 28th turned into the worse traffic nightmare since “Snowjam” 1982. People were stuck on the roads and in schools for up to 24 hours. Most everybody blamed the government for its lack of preparedness. I beg to differ. We all knew we were going to see 1-2 inches of snow followed by an arctic cold front. We knew it was going to develop in the late morning and continue into the evening. However, people chose to go to work. Schools chose to have class. Then it began to snow and everyone left work and school at the same time. All the traffic on the roads caused a massive snow melt which abruptly turned into ice with the cold arctic air moving in. Trucks to treat the roads could not get to their destinations and then the public said the government should have been more prepared. It was actually the residents of north Georgia that were not prepared and did not take our forecasts seriously and caused the chaos.
When we were forecasting the snow, sleet, and ice again two weeks later, people heeded the warnings and we avoided a repeat performance. Gov. Nathan Deal in the days after the January 28th storm, appointed a task force, of which I am a member. We have met several times and have made some excellent suggestions on how to address future winter storms. I am also doing a lot of the forecasting too. Although winter is just about over, I have reminded the task force about March 13, 1993! While seeing another “Storm of the Century” is not likely, you never know, especially with this weather pattern we are in.
Speaking of weather patterns, it is likely we are going to see the strong southern branch of the jet stream continue to traverse the southern United States through the spring. It wasn’t a week after our snow, sleet, and ice that we were under a tornado watch with violent overnight storms causing trees to crash into homes. I suspect we are going to have a very active tornado and severe storm season if the pattern holds. I cannot emphasize enough that we all need to be prepared. You need an app that has a warning alert for your smart phone. We have a great weather app that I think is the best in the country. It is free on iTunes. If you don’t have a tablet or smart phone, you need to get a weather alert radio. Whenever there is a severe storm threat, you will have critical weather information when you need it, even if the power goes out. Take for example our first round of severe storms back in February. They moved in during the middle of the night when most of us were asleep. Getting a warning from your smart phone, tablet, or weather alert radio can and does save lives.
February 2014 column
So just what is a 'polar vortex'?
As we move out of a record setting cold January for much of the eastern two thirds of the country, our long-range models show we can expect a nice warming this month.
Last month we all heard ridiculous headlines like “the polar vortex is set to devour the Midwest and Northeast.” I think a little explainer about the polar vortex is in order. I believe we all know or have at least heard of, the Bermuda High. In the summer, it’s a semi-permanent area of high pressure centered near Bermuda. It’s what keeps us warm and muggy during the warm months. It’s also a guide for hurricane movement. In the winter, the Bermuda High migrates eastward across the Atlantic and sets up near the Azores. It then becomes known as the Azores High. It’s pretty much the same thing with the Polar Vortex. It’s a semi-permanent area of low pressure centered near Baffin Island. The polar vortex, as it sounds, is circulation of strong, upper-level winds that normally surround the north pole in a counterclockwise direction – a polar low-pressure system.
These winds tend to keep the bitter cold air locked in the Arctic regions of the Northern Hemisphere. It is not a single storm. On occasion, this vortex can become very weak and can become distorted and dip much farther south. When this weakening occurs (called a negative north Atlantic Oscillation) frigid arctic air is allowed to plunge much farther to the south than normal. This is why we saw the record cold across much of the country, including a 6 degree record low here in Atlanta earlier last month.
The north Atlantic Oscillation models show it going into the positive range this month and therefore, we can expect a nice warming trend, at least for the first week or two. That is as far as the model data goes out. The Climate Prediction Center is a little more confident, indicating above average temps for the entire month. So, if you like warm temperatures, this is certainly good news for you.
On the other hand, this may not be such good news for those of us in the meteorological community. When we see a rapid thaw after harsh cold, we tend to see above average severe weather. Climatologically, severe storm season begins this month along the southern gulf coast states, from Louisiana to the Florida Panhandle. The reason being is this geographic area tends to get warmer first. That being said, we have certainly seen our fair share of violent storms and tornadoes in Georgia in February. With temperatures warming, and it could be a significant warming, the battle zone between cold air and warm air could be accelerated northward. There has also been another weather feature we have taken great note of this winter. Our jet stream is split over the continental United States. The cold polar branch wavers across the country like a snake bringing down the cold arctic air. The southern branch of the jet stream is riding hell-bent across the Mexican Baja into the southeast. This river of air running at nearly 80 miles per hour churns through the atmosphere at around 18,000 feet. When these strong upper level winds cruise over thunderstorms, they add a tremendous amount of energy and wind shear. Tornadoes and severe thunderstorm winds will now be our focus of attention. After such an active winter, we will have to wait to see how weather patterns continue to evolve.
My best advice, be prepared. Severe storm season is almost here.
January 2014 column
'Neutral' conditions make weather predictions difficult
Last month I attended a winter weather seminar at the Georgia Tech Research Institute. Along with Atlanta TV meteorologists, attendees included representatives from Georgia Emergency Management Agency, county emergency managers, and meteorologists from the Atlanta National Weather Service. The goal of the seminar was to look back at past winter weather events and to see how the National Weather Service, GEMA, and county emergency managers handled these events. We went over how soon winter weather advisories, watches, and warnings should be issued, if the warning terms or parameters should be changed, and what would make the public more aware of impending winter weather. Then a GEMA representative dropped the bomb and asked Keith Stellman, Meteorologist-In-Charge of our National Weather Service, what he thought we could expect this winter.
There was about five minutes of head scratching. Stellman finally replied that he was just not sure. He went on to say predicting long term weather in a “neutral pattern” was extremely difficult. When we have an El Nino, which is above normal sea surface temperatures in the eastern or central equatorial Pacific Ocean, we know we’re going to have a wet and cool winter. When we have a La Nina, which is ocean cooling in the Pacific, we know we generally have warmer and drier winters. However, since we don’t have either this winter season, the predictions are a little more difficult. Stellman said, based on the latest long-range model guidance, we might see some wintry weather during the third or fourth week in January. Climatologically, that IS when we get most of our snow or ice.
The problem I have been dealing with in my own forecasts is the jet stream, or should I say jet streams. Moving from west to east across the country is a river of air containing powerful upper level winds. The jet stream separates cold air from warm air. The bigger the difference between the cold air and warm air, the stronger the jet stream winds. We always look at the position of the Polar Jet to determine when cold air will move into north Georgia. This winter season, we are dealing with the Polar Jet and also the southern branch of the jet stream called the Sub-Tropical Jet Stream.
While the polar jet brings in cold air, the sub-tropical branch has been transporting storms from the Pacific Ocean through the southern states. It was responsible for that big ice storm across Texas last month. Stellman and I agree that because there is so much cold air and snow on the ground to our north, we will see the Polar Jet driving farther south during the month of January. With the southern jet bringing in one pacific storm after the other, it will only be a matter of the cold air and a pacific storm meeting up here.
My bet for wintry precipitation this month will be ice and snow. Timing of course, is everything. We’ll continue to watch the weather and will always keep you once step ahead.
Until then, I hope you all have a wonderful and prosperous 2014.
December 2013 column
More artic fronts predicted this winter
It is hard to believe that another year is coming to a close. Last spring’s tornado season was much quieter than normal. The Atlantic hurricane season turned out to be a non-hurricane season, despite dire predictions. However, this past fall turned out to be devastating for many people in the United States and around the globe. From Super Typhoon Haiyan in the Philippines to the 80-plus tornadoes that slammed the Midwest in November, this past autumn brought a great deal of destruction. So far, we in Georgia have fared well this fall severe storm season. However, we all know strong and severe storms can occur any time of the year. We have seen many tornadoes in late December and January.
I have been doing a great deal of research on something with the folks at NASA’s Jet Propulsion Laboratory in California. Scientists working at NOAA, the National Oceanic and Atmospheric Administration found a conclusive link between the alignment of two weather patterns in the Northern Hemisphere and the formation of an “atmospheric river” headed for California. The results were obtained in part from data provided by NASA’s 11-year-old Aqua weather satellite.
Atmospheric rivers are narrow bands of wind, often a mile high that can pack the punch of a hurricane. As they move over the ocean, they become laden with water vapor and can carry with them as much water as the Mississippi River dumps into the Gulf of Mexico in an average week! An example of the power of such an atmospheric river event was seen in 1999, when a winter storm hit California and caused 15 deaths and $570 million in damage. The two weather systems studied were the Arctic Oscillation and Pacific/North American teleconnection. The weather patterns rarely align in a certain way, but when they do the result is intense weather for California. Most troubling is that the weather events have the possibility of playing out over an extended period of time – such as the winter storms in 2010-2011.
So why should we be concerned with storms on the opposite side of the country? Let’s take a look back at what has happened this past fall. Normally, we see five to six true arctic cold fronts every season. By late November, we already had three. The arctic high pressure systems have been setting up across New England for the most part. This position sets up that wedge of cold air that drains down the Appalachian Mountains into north Georgia and sits there for days on end. There has also been a very strong southern branch of the jet stream traveling from California, across Texas, and into the Southeast. So, if we have strong southern storms moving from California into the Southeast and there is a “wedge of cold air” in place, the end result could be a major ice storm. On average, north Georgia is likely to see a major ice storm once every 10 years. We are way overdue.
I would like to wish you and your family and very Merry Christmas and a happy and wonderful New Year. And I will end this article with the question that everyone wants to know. What our winter weather should be like. Unofficially, my prediction is for temperatures to be slightly below average with several more major arctic fronts with above average precipitation. The official forecast from the Climate Prediction Center is for equal chances for above or below average temperatures. That being said, the CPC is predicting above average temperatures from Alabama westward through the desert Southwest. Being in such close proximity to the warmer than average temperature prediction, I would think we are going to have temperatures near normal to slightly above normal. The forecast for precipitation is for below average precipitation from December through February.
November 2013 column
Yes, it was a typical October
October certainly lived up to its expectations. Our summer humidity moved out. Temps for the most part, were typically cool, and we did not see a lot of rain. I was concerned about Tropical Storm Karen in early October, not so much from the wind, but from the heavy rains tropical systems could potentially bring. With our moist soil from the summer rains, a heavy rain-maker could have caused some serious issues.
Fortunately, after states of emergency were declared from Louisiana to Alabama, hundreds of thousands of dollars spent on moving boats inland, and the news media outlets just about calling it the storm of the century, Tropical Storm Karen only brought a few rain showers to the gulf coast with winds in 20 mph range before it completely fell apart.
I certainly loved the kind of weather we had during October. However, I also know October is the calm before the storm. November is a month of transition. Winter weather patterns begin to become more defined. Cold fronts continue to get stronger and more frequent. It is time for the autumn weather wars to begin, the time for air masses to collide. The battle ground this month is the Southeast.
During the month of November we often see lines of storms developing ahead of approaching cold fronts. Most of us know these as squall lines. They are in fact, what we call a QLCS or quasi-linear convective system. They are powerful, often containing “bow echoes,” which indicate strong straight line winds. On occasion, when we get enough wind shear (changing wind speed or direction with height) we will get a tornado spinning up on the leading edge of the bow echo. They are extremely difficult to find because they are very small. They do however create powerful winds of more than 100 miles per hour. These systems will often cross states ahead of a cold front and are easily tracked by our radar. Fortunately, with the new technology we have, we can spot the rotation much better. We can even see if it is lofting debris in the air. Even without a tornado, winds can reach 70 mph in the bow echo straight line wind area. These are dangerous thunderstorms. I just want all of you to be aware November can produce the kind of storms we see in the spring.
With that being said, November certainly has its fair share of magnificent weather days. It will be getting colder and on average, our first frosts and freezing temperatures can be expected during the first couple of weeks of the month. I know you all want to know if it will be a cold winter. I wish I could answer that right now. However, as I mentioned, weather patterns are just now taking shape for the winter. The Climate Prediction Center gives us, once again, a 50-50 chance of above or below average temperatures and rainfall this winter. I know what you are thinking but we have to cut the CPC a little slack. We don’t have an El Nino or a La Nina right now. When those conditions exist it makes winter weather predictions much easier. We are currently in a neutral pattern, which tends to complicate things.
You may recall last spring when all the tropical weather experts were saying how bad the hurricane season was going to be. As it turned out, the tropics were as quiet as Lake Lanier during as ice storm! If you would like my humble opinion, I think the western United States will be warmer than average while we here in the Southeast enjoy a good old-fashion, normal Georgia winter with occasional cold fronts, a couple of days of flurries or snow showers, and no doubt a few days of sunshine and 70s thrown in from time to time.
No matter how it turns out, I wish you and your family a happy Thanksgiving and a great November. I am sure by next month, weather patterns will have established themselves and we’ll know more as we head into winter.
October 2013 column
The feel of fall is in the air
October is without a doubt, my favorite month of the year. Cool fronts become stronger and more frequent resulting in that “feel of fall” in the air we all enjoy. October is also the second driest month of the year, averaging 3.41 inches. (April is the driest month, averaging 3.36 inches).
The fall color is certainly making its presence known this month, especially the last week of the month. Everyone is asking what my prediction for fall color will be. Based on my experience, I think the above average rainfall we have had would mean less brilliant fall color this year. That being said, I also believe the good soil moisture we still have will mean a longer season.
Speaking of above average soil moisture, my thoughts quickly turn to the tropics. It has been a rather unusual tropical season this year. We have seen an increase in dry air and dust from the Sahara keeping the Atlantic in check and really limiting tropical storm development. However, in October, the most likely area for tropical storm development is much closer to home, in the Gulf of Mexico. As I pointed out, cool fronts will be moving through north Georgia with greater frequency this month. As they move through, they have a tendency to stall out in the Gulf of Mexico. Often times, we see low pressure areas develop along these stalled boundaries. These low pressure areas can sometimes “spin up” into tropical systems. With the Gulf being very warm and with many warm water eddies, there is plenty of fuel for a tropical system to develop and get stronger. I am not so much concerned with the wind from any developing system as I am for the rains they can bring. In recent conversations with our state hydrologist, a system that has the potential to bring 5-10 inches of rain to our area could be devastating. So, we’ll certainly be keeping a watchful eye on what happens this month.
I know you are all wondering what this fall and winter will be like. I am wondering too! This year we are in what we call a neutral pattern. That means we have no Pacific Ocean cooling, ( La Nina) or Pacific Ocean warming, (El Nino) to change the global wind patterns. We know what type of weather a La Nina or El Nino tends to bring. However, in a neutral pattern we really can’t make a winter weather prediction until we begin to see how weather pattern across the globe are evolving. As of right now, the Climate Prediction Center is forecasting near average or slightly above average temperatures for the winter months. The CPC is also forecasting drier than average weather for the winter. I would assume this is subject to change so stay tuned!
Enjoy the beautiful blue October skies, the mild temperatures, and the beautiful colors of Autumn.
September 2013 column
Records set in rainfall, cool temps
Last month was one of the strangest weather months I have ever seen. Our wet pattern continued and on August 19th, we surpassed our average annual rainfall total of 49.68 inches! The weekend of August 17th, we saw the coolest high temperature ever recorded for the date, which was 66 degrees. We shattered the old record of 74 previously set in 1892!
So what is going on with our weather? The first observation I can make involves the position of the Bermuda High. The Bermuda High is a semi-permanent area of high pressure that, in the winter months, is centered in the eastern Atlantic Ocean near the Azores. During the summer, it migrates across the Atlantic and sets up near Bermuda. I have seen its position a little farther west than the past couple of years. Normally during the summer we get a southwest wind off the Gulf of Mexico, which sets us up with afternoon thunderstorms. With the Bermuda High being a little farther west, we have not only seen moist air coming off the Gulf, but moisture coming in from the deep tropics. In essence, we have become a tropical rain forest this summer. The air is so loaded with moisture that extreme rainfall, sometimes two to three inches per hour, is the result.
With the position of the Bermuda High being a little farther west than in previous years, there is great concern among the southeastern meteorological community. We are now in the peak of the Atlantic hurricane season (the actual peak is September 15th). If the Bermuda High was centered more toward the east, then tropical systems that develop in the Atlantic would ride around the western ridge of the high and then run parallel to the east coast, most remaining well off shore. However, given the Bermuda High’s current westward position, the western ridge would bring tropical systems right up through the Gulf of Mexico, across the Florida Panhandle, and right up into Georgia. This would not bode well for us at all.
Our groundwater tables are full. The lakes are full. The soil is already saturated. Many areas have seen so much runoff from the tropical rains, massive tree roots are now exposed. Our National Weather Service hydrologist, Kent Frantz, is extremely concerned about mud slides. The worst case scenario would be a storm like Hurricane Opal. We would not only see heavy tropical rains but tornadoes and severe wind damage. I cannot imagine the number of trees that would go down in north Georgia. That being said, we could also get a storm like Tropical Storm Alberto in July of 1994. It was a weak storm as far as winds go, but the rains it brought, especially to south Georgia, were catastrophic. Either scenario is something we need to be prepared for.
I do have a bit of good news. The long-range 90 day weather outlook takes the above average rainfall and brings it more to our west and northwest. The Climate Prediction Center gives us 50/50 odds of having above or below average rainfall over the next 90 days. We shall see.
In any event, cooler temperatures will be arriving by the end of the month as we close out a summer for the record books. The first day of fall is Sunday, September 22nd, at 4:44 pm.
The full Harvest Moon is September the 19th. Hope you have a wonderful September. I will return with our Winter Weather Outlook next month.
August 2013 column
Blame the rain on the Bermuda High
After so many years of reporting drought conditions and low lake levels, we have seen a remarkable and dramatic recovery. I realize we have not had the best weather this summer, however, I happy to report an extremely healthy rainfall surplus of over 15-inches for the year! Every single north Georgia lake is at full pool. The underground water table has been replenished and lawns and gardens are green and lush, even in these Dog Days of Summer.
You are no doubt wondering what brought on this change and the end to our drought. It all has to do with the Bermuda High. In the winter months, the Bermuda High is called the Azores High. It’s a semi-permanent high pressure area that, in the winter, migrates to the Azores in the eastern Atlantic. In the summer, it migrates into the western Atlantic and centers over Bermuda. It is the same high pressure area that causes most hurricanes to ride around its western flank and up the Atlantic Coast, hopefully remaining offshore of the Atlantic seaboard. This summer, the Bermuda High has set up a little more to the west than usual.
At the same time, there have been massive areas of low pressure to our west, centered across Texas. (Texas has also been in a severe drought but has seen some good rain this summer.) These low pressure areas have a counterclockwise wind flow pattern. So we have the Bermuda High and the Texas Lows working like giant atmospheric cogs in a machine, funneling in tremendous amounts of moisture from the Gulf of Mexico and the Atlantic Ocean, across the Southeast. You combine that kind of moisture-laden air with summer heat and you have an enormous amount of rain. That is also a major concern.
As we now move into the heart of the Atlantic hurricane season, my major concern is with the Bermuda being a little further west than usual, it may funnel in a tropical weather system. It doesn’t even have to be a hurricane or even a tropical storm. A slow moving tropical depression could bring incredible amounts of rain to north Georgia. With an already saturated ground, flooding will be an ongoing concern. There is a little bit of good news. NOAA has revised its forecast for an above average number of Atlantic storms downward. Let’s all hope the prediction holds.
Enjoy the rest of your summer. Fall officially begins on Sunday, September 22nd.
July 2013 column
New technology to track thunderstorms
July is certainly a very unique month. Aside from being the hottest time of the year, summer storms will fire up somewhere in north Georgia each and every afternoon. The majority of our afternoon storms are called “pulse type” because then tend to pulse up and then fade away in about an hour. However, as the get to their “mature stage” they can be very violent. On a hot summer afternoon, warm air rises up from the ground and can actually form a “cap.” Thunderstorms like to form as warm humid air rises rapidly into a pool of colder air aloft. With a cap of warm air above the ground, the updrafts rise and try “punching” their way through. They will usually have little success developing until that cap breaks. When it does, storms will be explosive, like the ones that occurred last month on June 14th.
Here in Severe Weather Center 2 we monitor the situation with special models that can actually show which of those little puffy clouds will grow into a monster summer storm. These models were actually developed by the University of Alabama at Huntsville. This is the first season we have used the new model guidance and it seems to be performing quite well. This will ultimately lead to better thunderstorm forecasting and warnings. The new model will actually color code clouds from the satellite. Each color from blue, green, yellow, orange, and red will indicate a percentage probability of it developing into a thunderstorm. This is astounding technology. Although still in development, we will be using this product on the air beginning this month. So imagine a nice hot July afternoon with a few puffy clouds to the west of Lake Lanier. You obviously don’t want to be heading out with approaching thunderstorms but you also know there is a chance some could develop anywhere in north Georgia. Now we can tell you with greater certainly where pop up afternoon storms will actually pop up.
Our main concern with July storms is lightning. As I mentioned, updrafts of warm air go to great heights in the atmosphere. Despite ground temperatures in the 90s, at 18,000 feet the temperatures are at or below freezing. In this environment, the updrafts of warm air are very strong and will actually carry falling raindrops back up into the cloud where they will freeze and refreeze into hail. The hail will collide with other raindrops and supercooled water in the clouds and this will create the static charge. From that charge, we see lighting, which often times in July, is fierce. More often than not, we track 50 to 100 lightning strikes every 10 minutes in just a single afternoon thunderstorm. Usually 5-10 percent of these are the positive strikes that leap out 15-20 miles from the parent thunderstorm. The positive lightning bolts are hundreds, even thousands of times more powerful than the negative strikes. In fact, I remember tracking a storm with fierce lightning in southeast Cobb County and a lightning bolt hitting a man mowing his lawn on a tractor in Gwinnett County!
Take summer storms seriously and make sure you have something on your mobile device to warn you of impending storms when you are out on the lake. You may not have much time to react and take cover so be prepared.
June 2013 column
Social media asking, 'Where's spring?'
I cannot tell you how many emails and facebook questions I received last month. It was astounding. Everyone wanted to know what happened to spring. It was abnormally cold as we all know. It was not just Georgia, as much of the eastern two-thirds of the country saw below average temperatures. After doing a considerable amount of research, I found it was the second coldest spring on record, after 1975!
The unseasonably chilly air did have a silver lining. We had far fewer tornadoes across the country than average. I know there was the big outbreak with 16 reported tornadoes near Dallas, Texas on May 16th, however the overall numbers were way down compared to seasonal averages. One reason for the lower tornado numbers was the unseasonably cool air that covered much of the country. Tornado outbreaks are the result of “weather wars” between cold air and warm air. There was no “battle zone” and no clash of air masses taking place. That of course, was certainly good news for us and for those that live in the heart of the nation’s tornado alley.
Summer officially begins this month on June the 21st. The Summer Solstice will be at 1:04 a.m. The question of the day now is, will we have an unusually hot summer after the cooler than average spring. The Climate Prediction Center certainly thinks so. It has predicted 85 percent of the country, everyone except the west coast, to have above average temperatures. I know the lake is up at full pool with the abundance of rainfall we have seen this year. The rainfall prediction gives us even odds of above or below average rainfall. That being said, the lake is full, soil moisture is good, and the underground aquifers are all in great shape to withstand a hot summer. Honestly, I cannot remember reporting anything like that in about 15 years!
While summer officially begins this month, hurricane season also begins. Predictions are all over the board. This is what is called a “neutral” year. We have no El Nino and no La Nina. When we have an El Nino year, we see strong winds from west to east across the Atlantic Ocean. This inhibits hurricane development because the strong high altitude winds tend to shear the storms apart before they have a chance to grow. La Nina years increases hurricane formation. However, we have neither and that is why the predictions range from above or below average numbers of tropical systems. The breeding ground for any tropical storm formation this month is down in the Gulf of Mexico. In July the favored breeding ground shifts to the Caribbean. During August and September, the “big ones” form off the west coast of Africa and “feed” on the warm ocean waters for days or even weeks, as they get stronger. My bet is for a typical hurricane season. That would mean 11 tropical storms, six of which will become hurricanes. We shall see.
In the meantime, I am going to enjoy Lake Lanier’s full pool and have some fun this summer. I hope you do too. It’s been a long time coming!
May 2013 column
Why there have been so few tornados - so far
Since the beginning of the New Year through this past April, we have seen a very low number of tornadoes in Georgia compared to what we saw in 2011. Across the United States the number of tornadoes has also been well below average. In April we had 43 tornadoes reported nationwide compared to 206 at this same time last year and in 2011 there were an astounding 1,200 tornadoes reported. So what was going on in 2011?
Some of the blame for the wild tornado streak lies with La Niña, a cyclical system of trade winds that cools the waters of the equatorial Pacific Ocean. (El Niño is La Niña’s warm-water counterpart.) Although we were in the grip of one of the most powerful La Niñas on record in 2011, La Niña made a sudden exit before the winter of 2011 ended. La Niña would have been beneficial for all the people that were hammered by the number of tornadoes not seen since 1953. If La Niña had maintained its strength, perhaps we wouldn’t have seen so many tornadoes.
How do trade winds in the Pacific relate to deadly storms in the southern and central United States? It has to do with the jet stream, a high-speed air current that is essentially an atmospheric fence where cool, dry air meets up with warm, moist air – two of the main ingredients for severe storms. La Niña has a stabilizing effect on the jet stream, and pushes it to higher latitudes. Without La Niña around, the jet stream stayed farther south. The jet stream spent April and May draped across the middle of the country, where it had the chance to violently mix cool, dry northern air with warm, moist southern air. And in 2011, those two air masses have been on the extreme ends of the temperature gauge.
The lingering affects of the 2010-2011 winter record snowfalls and snow packs have kept northern air especially cold, and the strong La Niña fueled unusually hot conditions in the Southwest. In addition, the sea surface temperature of the Gulf of Mexico is between 1.8 and 2.7 degrees Fahrenheit warmer than average. The warm, moist air was the perfect fuel for severe weather. If there’s more moisture and the atmosphere is warmer, it’s more unstable, so there’s more potential there for severe thunderstorms to develop. Like gasoline on a fire, those extremes provide the potential for more storms, and more powerful ones. And when powerful thunderstorms run into the windy conditions that occur each spring, they often begin to spin — and sometimes with horrifying consequences. The tornado that devastated Joplin, Mo., killing at least 125 people, is not only the deadliest single tornado to strike the United States since 1947, but the storm has now been upgraded to an EF-5, the most intensely damaging tornado on the Enhanced Fujita Scale, with winds in excess of 200 mph. It was the fourth EF-5 tornado in 2011. In contrast, a single EF-5 hit the United States in 2008, one hit in 2007; before that, the last EF-5 struck in 1999.
As we move into May, I am still concerned about more Georgia tornadoes since we have had such an unusually cool spring. As our temperatures continue to warm, battles between cold and warm will still be raging. I suspect from time to time, that battle ground will be here.
April 2013 column
Technology enhances tornado tracking
The date was April 9, 1998. We were in the middle of our north Georgia tornado season. We were watching our radar intently at a developing super cell thunderstorm west of Birmingham, Ala. The storm was beginning to form the large hook echo on its southwest side. We all knew what that meant. A tornado could be forming at any time. As it continued its rapid movement from the southwest to the northeast, there was no doubt where it would be headed next – Atlanta.
As it approached, our radar was picking up an enormous of hail surrounded by incredible amounts of lightning. The hook echo was becoming more pronounced with each scan of the radar. We knew we were going to see its powerful straight line winds first. We were not disappointed. The winds were gusting beyond hurricane force: 74 miles per hour. As it moved across the city, the hook echo was now extremely well defined. We assumed we had a tornado. We did and it became known as the Dunwoody tornado. It struck parts of the four most populous counties in Georgia: Cobb, Fulton, DeKalb, and Gwinnett. The most severe damage was in the Dunwoody area, where the storm reached a high-end F2 on the Fujita scale, making it one of the strongest and most damaging recorded to have hit that area. The thunderstorm was part of a major outbreak that started in the south-central Great Plains on April 6. The particular super cell which produced it did indeed spawn a tornado that ripped through western suburbs of Birmingham just a few hours earlier, as we learned later that day. The Birmingham tornado was rated at F5, a nearly unprecedented event in the southeastern U.S., and rare even in “tornado alley.” The F5 tornado is often called “the finger of God” because no