Winter rains ease Southeast U.S. drought; Brazilian storm could go subtropical

By: Dr. Jeff Masters , 5:59 PM GMT on February 29, 2008

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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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60. Patrap
7:29 PM CST on February 29, 2008
March 12-14, 1993 NARR Superstorm animation ...
800 x 600 - 621k - gif Link

Member Since: July 3, 2005 Posts: 414 Comments: 125613
59. Ivansrvivr
1:23 AM GMT on March 01, 2008
CC, I'm not just going by the models, but a little history. The 2nd storm has many similarities to the 93 superstorm. Only difference is el Nino influenced that one, this on is La Nina. Early March, Cold air behind 1st system, Low forming in GOM, deep tropical connection, all the ingredients are there, it's a matter of track and timing. I doubt the 2nd storm will be of '93 magnitude, but the similarities are there if it pans out.
58. NorthxCakalaky
1:00 AM GMT on March 01, 2008
Statement as of 6:53 PM EST on February 29, 2008


... Brief snow showers to produce light accumulations in parts of
the North Carolina mountains this evening...

... Snow Advisory in effect until midnight EST tonight...

The National Weather Service in Greenville-Spartanburg has issued
a Snow Advisory... which is in effect until midnight EST tonight
from Yancey to Avery counties in the northern North Carolina mountains.

Widespread rain showers will steadily mix over to snow showers
across the advisory area this evening. Light accumulations around
one inch will develop across most of the advisory area... with up
to two inches possible at higher elevations above 3500 feet. The
snow showers will likely briefly change back to rain showers
shortly after midnight... with precipitation ending as flurries
toward daybreak.

A Snow Advisory means that periods of snow will cause primarily
travel difficulties. Be prepared for snow covered roads and
limited visibilities... and use caution while driving.




57. stormdude77
8:41 PM AST on February 29, 2008
Hey y'all

Please check out my La Nina update, on my blog, see here.
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56. cchsweatherman
7:15 PM EST on February 29, 2008
53. Ivansrvivr 6:45 PM EST on February 29, 2008
I'm thinking the 2nd may be quite a bit stronger than the first.


We will have to wait and see about that, but at this time, I do have to agree with you. The models show the second storm becoming stronger than the first.

Member Since: April 14, 2007 Posts: 8 Comments: 5030
55. NorthxCakalaky
11:49 PM GMT on February 29, 2008
Rain!!! Much needed rain is falling here in north-west N.C. Very light rain and gusty winds.Starting to change to snow above 3000f.t.
1-2inches on the western slopes.Else where, less than half a inch in the mountain areas.Most of N.C wont get any measurable rain.
Info from weatherunderground.

Hopefuly next Tuesday we will get some heavy thunderstorms.
54. Ivansrvivr
11:45 PM GMT on February 29, 2008
STL, given the state of the nation, among other things, i'm leaning towards 1930's dust bowl type drought. If I remember right that one was at the end of AMO, and coincided with economic downturn. (Sound familiar?)
53. Ivansrvivr
11:43 PM GMT on February 29, 2008
I'm thinking the 2nd may be quite a bit stronger than the first.
52. cchsweatherman
6:32 PM EST on February 29, 2008
48. Ivansrvivr 5:57 PM EST on February 29, 2008
CC: Think either of the next 2 forecast storm systems will bring some more needed rain to the Fl Peninsula?


To answer your question, I do believe that you could see some severe storms capable of producing very heavy rainfall by late Monday into Tuesday associated with the first storm. I have not done enough analysis to respond upon the second forecasted storm, although I did see the storm in the models. Seems like it develops on the backside of this first storm. Quite interesting.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
50. scwindsaloft
6:12 PM EST on February 29, 2008
And yet another round.......

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49. Ivansrvivr
11:00 PM GMT on February 29, 2008
1928 storm is almost impossible due to all the man made changes that have occurred between the lake and the 'glades. All the canals, and swamp draining that has been done around Lake O has changed the topography completely. There are areas vulnerable to surge around Lake O, but not the same areas as '28
48. Ivansrvivr
10:54 PM GMT on February 29, 2008
CC: Think either of the next 2 forecast storm systems will bring some more needed rain to the Fl Peninsula?
47. cchsweatherman
5:43 PM EST on February 29, 2008
Good evening all. To answer your question leftovers, that is not a tropical wave moving into Belize; rather it is strong easterlies interacting with a stationary boundary that remains from the front that passed through Florida earlier this week. Good observation though.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
46. Ivansrvivr
10:42 PM GMT on February 29, 2008
STL, I hope your'e right and were not seeing a longer term drought spreading from the southeast into Texas and surrounding areas.
45. CybrTeddy
10:42 PM GMT on February 29, 2008
If such a storm were to hit in 2008, the chances of such a failure are much lower, thanks to the low lake levels

Dr.Masters, and to all of us here. Let us pray that this does not get tested. I dont wish for a 1928 storm to hit near were i live.
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44. ShenValleyFlyFish
5:00 PM EST on February 29, 2008
One day it will dawn on the people of this nation that we are not gods and Mother (Nature) knows best. In the long run it would be cheaper to buy out all the folks who have settled in places not suited for human habitation and let Nature do the land reclamation. I do not hope to live to see that day as the only thing that would drive the point home within my lifetime is a calamity which would make Katring look like a tempest in a tea pot.
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42. Patrap
4:04 PM CST on February 29, 2008
Special Weather Statement NWS New Orleans
Statement as of 3:45 PM CST on February 29, 2008
Link
Member Since: July 3, 2005 Posts: 414 Comments: 125613
41. NEwxguy
9:32 PM GMT on February 29, 2008
If the La Nina stays this strong and the current storm pattern holds true the flooding is going to be serious in parts of the country,especially where there is deep snow cover.
Member Since: September 6, 2007 Posts: 862 Comments: 15079
40. Ivansrvivr
9:02 PM GMT on February 29, 2008
There are 2 good possibilities for rain for the lake in the next 10 days or so. That may be it until the rainy season (which may start later than usual due to La Nina).
38. BahaHurican
3:42 PM EST on February 29, 2008
Afternoon, all.

Somebody mentioned the 1950 hurricane season earlier (on the previous blog). It turns out that this was an interesting season. 11 hurricanes, including 1 cat 5, were packed into the period 12th August to 21 October. There was a 37 day period when there were at least two hurricanes spinning in the basin. I'm sure it's seasons like this that help to define that double spike pattern of the "average" hurricane season. Six of the 12 named storms impacted the US directly or indirectly. Cat 5 Hurricane Dog at one point packed 185 mph winds and 100 ft seas, but fortunately did not make direct landfall, despite the 130 mph winds felt in the Northern Lesser Antilles.

This was quite an interesting season.
Member Since: October 25, 2005 Posts: 19 Comments: 20733
37. Ivansrvivr
8:49 PM GMT on February 29, 2008
CCW: it is same old story of overbuilding w/o planning and infrastructure.
36. weathermanwannabe
3:42 PM EST on February 29, 2008
35. Ivansrvivr 3:42 PM EST on February 29, 2008
You have made some other valid points...Fact is that it is a very complex issue and you bring out something I did not want to mention earlier (even through much of my family lives down there!)......Humans shouldn't really be living on re-claimed swampland in the first place, or, in the direct shadow of the Lake, but, tell that to the politicians and property developers in Florida (or on the coast for that matter)......Don't get me started!...LOL
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35. Ivansrvivr
8:33 PM GMT on February 29, 2008
The adverse effects of L.O on wildlife(the Evergaldes etc.) are caused strictly by agricultural runoff(fertlilzers causing algae blooms, pesticides...) Those same folks using those chemicals have quite a bit of lobbying power with the State Gov. They also want the lake water for irrigation. That is the real reason we are under such heavy water restrictions, while coastal rainfall can't be used to replenish the lake w/o adverse effects.
34. latitude25
8:40 PM GMT on February 29, 2008
US Army Corp of Engineers
Frequently Asked Questions


What will be the condition of the lake when it returns to normal levels?

Numerous variables must be considered. Water levels that increase gradually
over the course of months will result in fewer negative impacts than if a tropical
system or other rain-producing weather event dumps great amounts of water
on
the lake over a short time span, causing the lake level to rise rapidly.

damned if you do
damned if you don't
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32. weathermanwannabe
3:23 PM EST on February 29, 2008
Either way (SFWMD) it is a huge effort to try and manage the limited "fresh" water resources available to South Florida (there is plenty of salt water intrusion to worry them as well)and as Dr. M. mentioned in his blog today, they will need some storms/hurricane to replenish the area before the Summer is over....If you ask me, based on what I have read below and what the future might bring, it would probably be a good investment (if they can afford it) over the long term to rebuid/reenforce the barriers around the lake, and, to keep the water levels as high as possible...But, this also brings problems ecologically as extremely high water levels in the Lake start to affect the ecosystem balance and wildlife.....Quite a daunting tasks (with water managers concerned about the human population and scientists-ecologists worried about the natural ecosystem) to keep both sides happy and safe.........
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31. weatherboykris
8:32 PM GMT on February 29, 2008
LOL.Look,my point is...no need to beat up the SFWMD.They did the right thing,and it would have made little difference at ths point.
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30. latitude25
8:27 PM GMT on February 29, 2008
kris

deep breaths

you're going to have a stroke
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29. weatherboykris
8:25 PM GMT on February 29, 2008
latitude..they drained it once!They did not purposely keep draining it,I don't know were you're getting that information from.They drained it after Wilma and before Ernesto(as is common protocol,they always drain when there is an immediate hurricane threat).
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27. weatherboykris
8:24 PM GMT on February 29, 2008
Your point?The lake was at least 17 feet,and may have been 19 feet,if I remember correctly.Besides,that FAQ is out of date,new info had come out questioning the validity of previous confidence about the dike.
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26. latitude25
8:21 PM GMT on February 29, 2008
US Army Corp of Engineers
Frequently Asked Questions


Is it true that Lake Okeechobee levels must be kept low to avoid
overtopping of the Herbert Hoover Dike during hurricanes?

No. The danger of Lake Okeechobee overtopping the Herbert Hoover Dike
(HHD) is extremely remote. In fact, if the HHD did not exist today, water would
flow into the lake because the lake’s elevation is below that of the surrounding
land. Even if the lake were to fill up and reach a level of higher than 17.25 feet,
the potential for flooding danger would not be from overtopping but from seepage
and piping, or internal erosion.

Link
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25. Ivansrvivr
8:13 PM GMT on February 29, 2008
Minor correction about SFWMD and lake levels. The Army Corps dropped the lake level after Wilma, but it was the SFWMD that drained the entire canal system that L.O. feeds days before the predicted landfall of T.S. Ernesto unnecessarily. That dropped the lake level another foot or more. That action was too early and too extreme. Despite what most folks hear, the canal system could be used to backfeed L.O if it was truly necessary.
24. latitude25
8:17 PM GMT on February 29, 2008
You are jumping the gun.
It's one thing to lower the level
It's another thing to maintain that low level because of a prediction.
The low level was maintained because of a prediction.

NOAA ISSUES UNSCHEDULED EL NIÑO ADVISORY Sept. 13, 2006

Link
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23. weatherboykris
8:11 PM GMT on February 29, 2008
And as TCW said,hindsight is 20/20.If a hurricane had hit that year.the dike had broken open and thousands had died,those people in charge would have been fried.Their careers would be over.They did the right,safe thing.
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22. weatherboykris
8:00 PM GMT on February 29, 2008
Once again latitude,you show you don't know what you're talking about.When they dumped the water(after hurricane Wilma),it was forecasted that La Nina conditions would be prevelant,NOT El Nino.No one was forecasting an El Nino.
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21. V26R
7:55 PM GMT on February 29, 2008
Interesting article on what I think was the last Tropical System in the South Atlantic

Link
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20. latitude25
7:49 PM GMT on February 29, 2008
"I could not stop laughing that the SFWMD made a huge decision that will affect the entire region just because of some PREDICTIONS!!!"

It was the Army Corp that made the decision, not really the South Florida Water Mang District. Dropping the level 10ft.

Not only based on the climate models predictions of hurricanes,
but also on the predictions of a strong El Nino.

Which was also wrong, and turned into the opposite
a La Nina.
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19. Geoman
11:30 AM PST on February 29, 2008
South Atlantic tropical cyclones seem to be unofficially named a lot like earthquakes; in the case of the latter, the name of the nearest major geographic feature to the epicenter, or of the area hardest hit is applied. I suppose that WMO feels that South Atlantic tropical cyclones happen so rarely that there is very little chance of getting them mixed up over the years. In a way, let's hope that it stays that way.
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18. weathermanwannabe
2:32 PM EST on February 29, 2008
Thanks Dr. M.......We'll need to keep our eyes on the Southern Gulf region this coming Monday for sure...........
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17. Skyepony (Mod)
7:18 PM GMT on February 29, 2008
Llyods did an assesment of risk on the lake O dike in 2006. The Dike is in bad shape. It is being used as it wasn't intended when built, as a dam to form a water resovior. The fill capasity was even increased above design causing farther proplems. Lake levels play a large role in the amount of ongoing erosion & increased chance of failer. There is mention of several unspecified times recently where failure due to internal erosion or tunnelling nearly occured & was stopped by the Army Corp. The panel's results were that there was grave & immenent danger it would fail & the whole region would be lost if something wasn't done. The work has begone because of Katrina & the dike's history. It's also far from completed. Until it's done, (enviromental phosphate cleaning is on going too) it's probibly in the overall best intrest of especially the 40,000 residents that are very close to the dike & the 5 million + residents that are protected by the dike, to keep it low.
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16. cchsweatherman
2:27 PM EST on February 29, 2008
15. Tazmanian 2:18 PM EST on February 29, 2008
dr m what about Catarina that was a South Atlantic Hurricane and they name it too so why would they not name this one? like they did with the South Atlantic Hurricane??? would we see 90L?


They did not name the storm. Catarina is the name of the island the storm hit in Brazil, not the storm name. I'm not sure if they would label an invest on this, but, it could be possible.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
15. Tazmanian
7:13 PM GMT on February 29, 2008
dr m what about Catarina that was a South Atlantic Hurricane and they name it too so why would they not name this one? like they did with the South Atlantic Hurricane??? would we see 90L?
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14. TheCaneWhisperer
7:03 PM GMT on February 29, 2008
I agree Kris. The southeast is very dependent on tropical moisture. Take those away and you get what we're experiencing right now.
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13. Skyepony (Mod)
6:44 PM GMT on February 29, 2008
Excellent update & thanks for following the South Atlantic storm.

Interesting article being put out about a paper being published in "Science" today. About how the majority of rain's nuculi is one type of bacteria that multiplies on plants, then is swept up by wind into the atmosphere where ice forms around it to cause precipitation. Then only a single bacteria needs to be dropped on a plant to multiply & be swept up again.
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12. weatherboykris
7:05 PM GMT on February 29, 2008
Thanks for the info Dr. Masters.
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11. JeffMasters (Admin)
2:04 PM EST on February 29, 2008
There is no naming system in place to name any tropical or subtropical storm that may form in the South Atlantic. I've told one of the senior forecasters at NHC they should put a naming system in place, but he said it was up to the WMO, any they were very unlikely to do such a thing. Here's nice MODIS image of the storm from 15:30 GMT today.

It is true that Lake Okeechobee was deliberately drawn down quite a bit prior to the 2006 hurricane season. I can't say I blame them, after what happened in 2005. The dikes on Lake Okeechobee would have been vulnerable to overtopping or failure, if a storm like the 1928 hurricane had hit in 2006. If such a storm were to hit in 2008, the chances of such a failure are much lower, thanks to the low lake levels.

Jeff
10. weatherboykris
6:58 PM GMT on February 29, 2008
Well,all I know is that it's no coincidence that the drought started as soon as we stopped getting strong tropical storms and hurricanes.And that goes for ALL of the southeast,not just Florida.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.