Sunday, September 4, 2011

Tornado watch until 10 PM tonight. Alternate EOC is activated. Conditions are being monitored.

 Effects from Tropical Storm Lee will continue into Tuesday.
Key Points for this event:
 The main impacts from Lee for our area will be:
o Heavy rain
o Dangerous rip currents, high surf, and hazardous boating conditions
o Isolated tornadoes
IR satellite image and Mean Sea Level Pressure at 5 AM CDT
The current weather picture:
Tropical Storm Lee was centered just offshore the central Louisiana coast, with maximum sustained winds around 45 MPH. Lee was moving north at only
2 MPH, and is expected to move slowly to the northeast across coastal Louisiana today and tonight, then across Mississippi and Alabama Monday and Tuesday as it weakens and merges with an approaching cold front. Although Lee was weakening as it interacts with land and ingests dry air aloft from the west, it was still producing bands of torrential rain (seen as red on this IR satellite image).
Emergency Manager Severe Weather Briefing September 4, 2011---Page 2
The following image shows the official forecast track from the National Hurricane Center for Tropical Storm Lee, issued at 4 AM CDT Sunday. There were no tropical storm watches or warnings in effect east of Destin, Florida.
Emergency Manager Severe Weather Briefing September 4, 2011---Page 3
Heavy Rain
As Lee moves slowly inland, rain will continue to spread from southwest to northeast across our area. Rainfall amounts are expected to range from about 6 inches at the Florida Panhandle coast to an inch or two in north Florida and south central Georgia, as shown on the following image:
These are the expected, AVERAGE storm total rainfall amounts from today through Monday night. Although these rainfall totals would not have a major impact (especially since they will be spread out over 2 days), isolated rainfall amounts of 2 to 3 times these amounts can occur when a tropical cyclone moves inland...even weak tropical storms like Lee. Thus isolated amounts exceeding 8 inches are possible, and that could cause flash flooding (especially if it occurs during a fairly short time frame). A flash flood watch has been issued for much of the region, roughly west of a line from Tifton Georgia to Monticello Florida. This watch may need to be altered as the day goes on, since the rainfall pattern of Lee can change significantly and affect this forecast. Please stay tuned for future forecasts and possible warnings.
Emergency Manager Severe Weather Briefing September 4, 2011---Page 4
Coastal Hazards
Surf heights along the Florida Panhandle Beaches will be 5 to 7 feet today (with occasional higher sets possible), and may increase to 10 feet or higher by Monday afternoon. The rough surf and gusty winds will create very dangerous conditions for swimmers and surfers through at least early Tuesday. Some beach erosion is also possible. Tides have been averaging 1 to
1.5 feet above normal tide levels early this morning, and these conditions will persist into Monday. By Monday night tides could be as high as 3 feet above normal along the coast of Apalachee Bay, which would coincide with the local high tide. This could cause some flooding of low-lying areas as storm tides approach 5 feet Monday night. A small craft advisory is in effect for all of the Florida Panhandle and Big Bend coastal waters for extremely high seas and strong winds. This advisory will likely be in effect until Tuesday.
Tornadoes & Damaging Winds
There is a slight risk of severe storms today through Monday night, including isolated tornadoes. The main threat today will be across the Florida Panhandle and adjacent coastal waters, but this threat may spread slowly inland later this afternoon and tonight. A more widespread, significant tornado threat is possible Monday and Monday night as Lee moves northeast across Mississippi and Alabama and merges with an approaching cold front.
The image on the following page shows the tornado threat for today, which is about 5 percent. This number may sound very low in the context of rain chances, but a 5 percent chance of a tornado occurring within 25 miles of a point is actually rather high. In addition to isolated tornadoes, isolated damaging wind gusts of 60 MPH are possible.
Emergency Manager Severe Weather Briefing September 4, 2011---Page 5
Summary:
 Rain bands from Tropical Storm Lee will move across the region today through Monday. This rain could be heavy at times, causing localized flash flooding.
 High surf and frequent, strong rip currents will be extremely dangerous for swimmers and surfers, and the very high seas and strong winds will also be hazardous to boaters. Above-normal tides will continue, with maximum storm tides approaching 5 feet along coast of Apalachee Bay Monday night.
 Isolated tornadoes and damaging wind gusts are possible today through Monday.

 

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