Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 12:16 AM GMT on November 10, 2009
Tropical Storm Ida is pounding the coasts of southeast Louisiana, Mississippi, Alabama, and the Florida Panhandle with high winds, huge waves, and heavy rain. At 6 pm EST, the Mobile, AL NWS office reported that coastal flooding had begun on Dauphin Island and at Fort Pickens in the Florida Panhandle. Surf heights of 5 - 8' are expected tonight on Dauphin Island as Ida storms ashore, and heights of 10 - 15' are possible from Fort Morgan, Alabama to Destin, Florida. Sustained winds of 40 mph were reported at buoy 42007 22 nm miles south of Biloxi, MS at 4:50 pm EST, and winds of 40 mph, gusting to 51 mph, were recorded at Dauphin Island, AL, at 7:06 pm EST.
Figure 1. Estimated precipitation from the Mobile, AL radar shows that up to four inches of rain has fallen over the Louisiana bird's foot of the Mississippi River. Heavy rains are falling in MS, AL, and FL, and will exceed four inches in many locations.
The highest surface winds seen by the Hurricane Hunters since 3 pm have been 70 mph. Infrared satellite loops show that the big thunderstorm blow-up responsible for the small patch of hurricane-force winds recorded at 3 pm this afternoon has waned, and it is unlikely Ida has any hurricane-force winds.
The intensity forecast for Ida
There is no change to the intensity forecast for Ida. The high wind shear of 40 knots currently affecting the storm is forecast to increase to 50 knots by midnight, when the center of Ida should be crossing the coast. With Ida now over waters near 24°C, some weakening is to be expected before landfall. We can't rule out the possibility of an isolated tornado when Ida makes landfall, but the Storm Prediction Center Discussion maintains that the airmass in place over the Gulf Coast is relatively stable, and prospects for an appreciable severe weather threat appear low. Winds of tropical storm force will be extend from Southeast Louisiana to the Florida Panhandle (Figure 2), but will not extend very far inland.
Figure 2. Cumulative wind forecast for Ida, issued by the HWRF model at 1 pm EDT today, 11/09/09. The HWRF forecasts that winds in excess of 50 knots (58 mph, dark green colors) will affect a swath of ocean from the tip of the Louisiana bird's foot to the coast near Alabama. Tropical storm force winds of 34 - 50 knots (39 - 57 mph) will affect a larger region, but will not penetrate very far inland. Image credit: NOAA/GFDL.
The storm surge forecast for Ida
Tides are almost 5.0' above normal at Shell Beach, LA (on the east side of New Orleans), 2.2 feet above normal at Dauphin Island, AL, and 1.7 feet above normal at Pensacola, FL (Figure 3). NHC is calling for a storm surge of 3 - 5 feet above ground level, which is a reasonable forecast even if Ida weakens further. A large stretch of coast will be subject to very high water levels for an extended period of time today and tomorrow, with battering waves on top of the surge likely to cause a significant coastal erosion event.
Figure 3. Observed vs. predicted water levels at three coastal stations. Top: Shell Beach, LA (just east of New Orleans); middle: Dauphin Island, Alabama; bottom: Pensacola, FL. The green line shows how high above normal the water is. For Shell Beach, it was 4.9 feet above normal at 6 pm CST, 2.2 feet at Dauphin Island, and 1.7 feet at Pensacola. Image credit: NOAA Tides and Currents.
Links to follow:
U.S. Severe Weather Page
Wundermap for the Gulf Coast of Alabama.
Long-range radar out of New Orleans, LA.
Coastal observations from the University of South Alabama.
Coastal observations from LSU.
Update on portlight.org charity errorts
The portlight.org disaster relief charity is gearing up to respond to any disaster needs from Tropical Storm Ida, and has sent a self-sufficient kitchen capable of serving 2000 meals per day to the Florida Panhandle region. They have another mobile kitchen ready to respond, if needed, as well as a truck filled with durable medical equipment and clinical/surgical supplies. Donations are welcome!
I'll have an update Tuesday morning.
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