The Monday afternoon web video is on the server:
http://beta.abc3340.com/weather/video.hrb
Just got the first tornado warning of the event from Oklahoma City... tornado warning for Alfalfa county in northwest Oklahoma.
Lots of people are wanting us to compare this event to other "red letter" severe weather days in Alabama, like April 8, 1998, December 16, 2000, November 20, 2002, etc...
That is a dangerous game. All it takes is one relatively small tornado coming down a populated street, and it becomes a red letter day. You can multiple F5 tornadoes in the middle of a rural wooded area in Alabama, knocking down thousands of trees but not impacting anyone, and it is just another day. So, every severe weather event has the potential to be a "red letter" day in Alabama weather history. And, every storm that looks truly historic can be a "no big deal" event. It all depends on what moves through the populated parts of Alabama.
Having said that, here are the peak NAM severe weather parameters forecast for tomorrow evening:
CAPE 2157
Lifted Index -8.0
0 to 3 km Helicity 204
Total Totals 57
SWEAT Index 471
Here are the parameters from jsut before the April 8, 1998 F5 tornado in Birmingham:
CAPE 2370
Lifted Index -8.0
0 to 3 km Helicity 220
Total Totals 61
SWEAT Index 641
You can look at those parameters all day, but the key to the April 8, 1998 F5 was a mesoscale boundary moving up from the south. We saw it as a fine line on radar, and as that boundary hit thunderstorms moving into west Alabama that is when rotation started, and the rest was history. There were no other significant tornadoes in Alabama April 8, 1998 other that the ones along that boundary. So, what we are saying is that the small scale features drive these events, and we really won't know about them until tomorrow morning or even at midday tomorrow.
Learn about these indices here:
http://www.crh.noaa.gov/lmk/soo/docu/indices.htm
OTHER THOUGHTS:
*SPC maintains a moderate risk of severe thunderstorms for just about all of Alabama tomorrow.
*We think the greatest risk of severe storms in Alabama will be from about 10:00 a.m. to 10:00 p.m.
*The 500 mb temp (about 18,000 feet off the ground) is projcted to be -17.6 (C) tomorrow evening, which means some very large hail could be involved.
*There is some school of thought that the surface warm front will set up somewhere along I-20 tomorrow, and might help to serve as a focus for rotating storms due to the higher 0 to 1 km helicity it would generate.
*No flash flood problems are expected... the NAM only spits out 0.45" in Birmingham for the event.
*I still have some concern about another severe weather event at some point over the Easter weekend, but lets get through tomorrow and then we will worry about that one.
On a number of instant message conferences with various NWS offices and the in-house group of meteorologists here...
We will post additional notes here this evening as needed!
http://beta.abc3340.com/weather/video.hrb
Just got the first tornado warning of the event from Oklahoma City... tornado warning for Alfalfa county in northwest Oklahoma.
Lots of people are wanting us to compare this event to other "red letter" severe weather days in Alabama, like April 8, 1998, December 16, 2000, November 20, 2002, etc...
That is a dangerous game. All it takes is one relatively small tornado coming down a populated street, and it becomes a red letter day. You can multiple F5 tornadoes in the middle of a rural wooded area in Alabama, knocking down thousands of trees but not impacting anyone, and it is just another day. So, every severe weather event has the potential to be a "red letter" day in Alabama weather history. And, every storm that looks truly historic can be a "no big deal" event. It all depends on what moves through the populated parts of Alabama.
Having said that, here are the peak NAM severe weather parameters forecast for tomorrow evening:
CAPE 2157
Lifted Index -8.0
0 to 3 km Helicity 204
Total Totals 57
SWEAT Index 471
Here are the parameters from jsut before the April 8, 1998 F5 tornado in Birmingham:
CAPE 2370
Lifted Index -8.0
0 to 3 km Helicity 220
Total Totals 61
SWEAT Index 641
You can look at those parameters all day, but the key to the April 8, 1998 F5 was a mesoscale boundary moving up from the south. We saw it as a fine line on radar, and as that boundary hit thunderstorms moving into west Alabama that is when rotation started, and the rest was history. There were no other significant tornadoes in Alabama April 8, 1998 other that the ones along that boundary. So, what we are saying is that the small scale features drive these events, and we really won't know about them until tomorrow morning or even at midday tomorrow.
Learn about these indices here:
http://www.crh.noaa.gov/lmk/soo/docu/indices.htm
OTHER THOUGHTS:
*SPC maintains a moderate risk of severe thunderstorms for just about all of Alabama tomorrow.
*We think the greatest risk of severe storms in Alabama will be from about 10:00 a.m. to 10:00 p.m.
*The 500 mb temp (about 18,000 feet off the ground) is projcted to be -17.6 (C) tomorrow evening, which means some very large hail could be involved.
*There is some school of thought that the surface warm front will set up somewhere along I-20 tomorrow, and might help to serve as a focus for rotating storms due to the higher 0 to 1 km helicity it would generate.
*No flash flood problems are expected... the NAM only spits out 0.45" in Birmingham for the event.
*I still have some concern about another severe weather event at some point over the Easter weekend, but lets get through tomorrow and then we will worry about that one.
On a number of instant message conferences with various NWS offices and the in-house group of meteorologists here...
We will post additional notes here this evening as needed!
on March 21, 2005, 3:26 pm
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