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Coastal Impact Summary

| October 4, 2013 @ 11:15 am

The forecast is based on three areas relative to the track of the center of Karen:
…the left side tropical storm force wind swath
…the core center swath
…the right side tropical storm force wind swath

The current NHC forecast brings the skinny black line (dotted in this case) over the southeastern tip of Louisiana in Plaquemines Parish late Saturday night just after midnight near Empire. This is slower than earlier forecasts and slightly to the left of previous track forecasts. It then makes a second landfall near Fort Morgan on the Alabama coast late morning Sunday.

Of course, these forecast tracks have an average error at 48 hours of about 70 miles, so the the forecast for any one location in the path will change based on how the track changes. The models this afternoon will be bolstered by lots of extra data from the Gulfstream jet aircraft flying around the storm environment to get clues as to how the atmosphere is set up. The data will be fed into the models.

The center swath extends about 40 miles to the left of the center and 60 miles or so to the right. The three portions of the swath are shown pretty well on this forecast track/wind swatch graphic.

10-4-2013 11-10-02 AM

So, here is an idea of what people in the three swaths can expect:

LEFT SWATH
…includes Houma, New Orleans, the entire Mississippi coast
WIND: 12-16 hours of tropical storm force gusts with sustained winds Saturday running 25 mph increasing to 40 mph by Saturday night. A few gusts to 60 mph. Onset of tropical storm force winds: 1 p.m. Houma, 4 p.m. New Orleans and Saturday evening along the Mississippi coast.
RAINFALL: Amounts will taper quickly to the west of the track. Officially forecasting 2-4 inches across southeastern Louisiana and Mississippi, but amounts may be closer to an inch.
STORM SURGE: Models indicate 3-5 foot maximum surge above normal levels along the eastern facing shorelines of St. Bernard and Plaquemines and the entire Mississippi coast into Mobile Bay.
RIP CURRENTS: High risk. Don’t get in the water.
TORNADOES: Very low risk.

CENTER SWATH
…includes Mouth of the Mississippi, entire Alabama coast over to Destin
WIND: 10 hours of tropical storm force (39 mph or greater) gusts and 3-4 hours of strong tropical storm force gusts (greater than 58mph). Onset of tropical storm force winds: 4 a.m. Sunday morning at Gulf Shores, later as you go east. Sustained winds will be pretty calm Saturday, averaging 10-15 mph from the E/SE, increasing to 15-35 mph during the evening and to sustained at 35-50 mph after midnight. Expect gusts to 55-65 mph Sunday morning. Winds will start quickly diminishing late Sunday morning.
RAINFALL: 2-4 inches expected in this zone with isolated 5+ inch amounts.
STORM SURGE: 3-5 feet possible in coastal Alabama, with 1-3 feet along the Northwest Florida coast. This is above the normal levels you see the ocean at various tidal heights.
RIP CURRENTS: High risk. Don’t get in the water.
TORNADOES: A risk of tornadoes will exist mainly for the Florida Panhandle into Southern Alabama starting late Saturday into Sunday. There is a lesser chance along the Alabama coast as well.

RIGHT SWATH
…30A Communities to Panama City
WIND: 10 hours of tropical storm force (39 mph or greater) gusts to 45-50 mph. Onset of tropical storm force winds: 8-10 a.m.m Sunday morning, later as you go east. Sustained winds will be pretty calm Saturday, averaging 10-15 mph from the E/SE, increasing to 15-30 mph during the overnight and to sustained at 35-40 mph Sunday morning. Expect gusts to 55-65 mph Sunday morning. Winds will start quickly diminishing late Sunday morning.
RAINFALL: 2-4 inches expected in this zone with isolated 5+ inch amounts.
STORM SURGE: 1-3 feet along the Northwest Florida coast. This is above the normal levels you see the ocean at various tidal heights.
RIP CURRENTS: High risk. Don’t get in the water.
TORNADOES: A risk of tornadoes will exist mainly for the Florida Panhandle into Southern Alabama starting late Saturday into Sunday. There is a lesser chance along the Alabama coast as well.

RAINS
An outer band is already bringing showers to coastal Louisiana late this morning. This will actually diminish this afternoon as the main circulation moves toward the coast. Most of the rain Saturday will be concentrated in southeastern Louisiana, spreading across Coastal Mississippi late Saturday night and into coastal Alabama after midnight Saturday night. But feeder bands will rotate northward during the day on Saturday, bringing periods of rain/storms to coastal sections on Saturday, spreading up into South and Central Alabama Saturday afternoon and Saturday night. But the Auburn game looks dry. There is a chance of a passing shower in Tuscaloosa, but no rainfall is expected during the Alabama game.

Category: Alabama's Weather, Tropical

About the Author ()

Bill Murray is the President of The Weather Factory. He is the site's official weather historian and a weekend forecaster. He also anchors the site's severe weather coverage. Bill Murray is the proud holder of National Weather Association Digital Seal #0001 @wxhistorian

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