Winter rains ease Southeast U.S. drought; Brazilian storm could go subtropical
The winter of 2007-2008 is in the books, as today marks the last day of meteorological winter (December, January, and February). Winter rains have eased the drought gripping the Southeast U.S., where the area covered by extreme to exceptional drought has shrunk by about 50% since the beginning of the year (Figure 1). Some regions of southern Georgia and southern Alabama, where winter rains have been more than six inches above average (Figure 2), are no longer suffering drought conditions at all.
Figure 1. Drought categories for the Southeast U.S. from December 25, 2007, and February 28, 2007. Image credit: U.S. Drought Monitor.
However, A large swath of the Southeast U.S., including Atlanta, Charlotte, and Huntsville, have received 1-4 inches of precipitation below usual for this time of year. The shortfall is particularly acute in northern Alabama, where Huntsville has received only 6.77" this year, compared to the normal 10.47". The below average rains during this winter rainy season bode ill for the summer, when drought conditions could easily return to last year's extreme levels. The Southeast badly needs one or two landfalling tropical storms or hurricanes in 2008 to help break the drought.
Central Florida surrounding Lake Okeechobee is also suffering from below average rains this winter. The lake, which reached its all-time low water mark of 8.82 feet on July 2, 2007, has risen to 10.02 feet, but this is still a record low for this time of year. The surface area of the lake has shrunk to about 2/3 of normal, and the water level is more than four feet below normal. Part of the reason for the record low lake levels is the fact that the lake was deliberately drawn down before the 2006 hurricane season, in anticipation of another very active hurricane season.
Figure 2. Departure of precipitation from average for January and February 2008. Image credit: NOAA Advanced Hydrologic Prediction Service.
The forecast
The short-range rainfall forecast is good for the Southeast, with significant rainstorms possible both Tuesday and Thursday. The longer range three-month forecast calls for a continuation of below average precipitation for the spring season, thanks to the continued presence of a strong La Niña event in the Equatorial East Pacific. La Niña events usually deflect the jet stream into a pattern that takes the Southeast U.S. out of the the usual storm track needed to bring typical spring rains. However, for the summer months of June, July, and August, NOAA's CFS Climate Forecast System Model is predicting a return to normal levels of rainfall over the Southeast U.S.
Severe weather outbreak coming on Monday
A strong low pressure system is forecast to develop over Texas on Sunday, bringing a slight chance of severe weather to eastern Texas Sunday afternoon. By Monday afternoon, the storm is expected to track northeastwards over the Ohio Valley, dragging a strong cold front across the south. A significant severe weather outbreak is possible Monday afternoon in advance of this cold front.
Interesting South Atlantic storm could become subtropical
An extratropical storm centered near 31S 30W, a few hundred miles east of the Brazil-Uruguay border, has begun to acquire subtropical characteristics and could become a subtropical storm this weekend. The storm is not expected to hit land. NASA/MSFC has a clickable satellite image of Southern Hemisphere one can use to zoom in on the storm. An ASCAT pass at 5:29am EST this morning showed winds of 50 mph near the center of the storm. Water temperatures are about 26°C, which is right at the boundary where tropical storm formation can occur. Subtropical and tropical storms are quite rare in the South Atlantic. I'll update this section of the blog through the weekend if the storm develops. There is no naming system in place to name any tropical or subtropical storm that may form in the South Atlantic. It would be up to the World Meteorological Organization (WMO) to institute such a scheme. The last time I checked into this, they had no plans to consider a naming system. Here's nice MODIS image of the storm from 15:30 GMT today.
Figure 3. Visible satellite image of extratropical low off the coast of Brazil that is beginning to acquire some subtropical characteristics. Image credit: NASA/MSFC.
Jeff Masters
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" Tornado Warning
Statement as of 8:09 AM CST on March 03, 2008
The National Weather Service in Shreveport has issued a
* Tornado Warning for...
Bowie County in northeast Texas...
this includes the cities of... Wake Village... Texarkana... New
Boston...
southern Little River County in southwest Arkansas...
this includes the city of Ashdown...
* until 915 am CST
* at 807 am CST... National Weather Service Doppler radar indicated a
severe thunderstorm capable of producing a tornado near New
Boston... moving northeast at 25 mph.
* The tornado will be near...
New Boston by 820 am CST...
Hooks by 835 am CST...
Ogden by 915 am CST...
The safest place to be during a tornado is in a basement. Get under a
workbench or other piece of sturdy furniture. If no basement is
available... seek shelter on the lowest floor of the building in an
interior hallway or room such as a closet. Use blankets or pillows to
cover your body and always stay away from windows.
If in Mobile homes or vehicles... evacuate them and get inside a
substantial shelter. If no shelter is available... lie flat in the
nearest ditch or other low spot and cover your head with your hands.
A Severe Thunderstorm Watch remains in effect until 100 PM CST Monday
afternoon for southwestern Arkansas and northwestern Louisiana and
northeastern Texas."
I am wishing for Sarasota,FL to get a good soaking. Off to work, see you all in the PM
421 AM EST MON MAR 3 2008
500 MB CHART AT 00 UTC SHOWED A DEEP POSITIVELY TILTED TROF JUST PREPARING TO EXIT THE ROCKIES AND MOVE INTO THE HIGH PLAINS. A
CLOSED LOW OF 546 DM IS ANALYZED JUST SOUTH OF GRAND JUNCTION CO. 500 MB TEMPS ARE QUITE COLD WITH THIS FEATURE...AS COLD AS -34C. SHORTWAVE RIDGING IS MOVING OFF THE U.S. EAST COAST. VAPOR IMAGERY INDICATES THIS UPPER TROF AND CLOSED LOW IS MOVING SSE INTO CENTRAL
NEW MEXICO. THE FUTURE MOVEMENT OF THIS FEATURE WILL BE KEY IN THE DEVELOPMENT OF AND MAINTENANCE OF EXPECTED SEVERE WEATHER IN THE
SOUTHEAST.
Good Morning Folks.........
Things are relatively quiet in the Gulf/SE right now, but, as the closed low drops down into Texas from New Mexico later today, we'll have to wait and see how the potential for severe weather develops as the front interacts with the warm flow and moisture coming up from the Gulf..........It will be interesting later this evening and into tommorow and interests around the Gulf will need to keep a close eye on their NOAA products and local weather alerts...................
See Yall Later this evening as the situation unfolds..........
PUCKER TIME!
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