Tropical Storm Ida Forecast Track Eyes Mobile Bay Landfall as it Weakens Rapidly


IdaRainbow

Tropical Storm Ida Satellite Loop (click for most recent)

IdaWV

Tropical Storm Ida Water Vapor Loop (click for most recent)

Hurricane Ida has behaved as expected for the most part. You can access the Mobile National Weather Service Radar Here. You can also tell from the satellite loop above, it doesn’t really look like a tropical cyclone anymore but instead a run-of-the-mill area of low pressure.    In fact, if you look at the Tropical Storm Ida Water Vapor Loop to the left, it really looks like it doesn’t have much in the way of tropical characteristics.  As it moved north during the day, it ran into colder water.  By the afternoon, it was over water with a surface temperature of 26 C which is below the critical level to sustain tropical cyclones.  As it moves north, it will move into increasingly colder water.  Also, it encountered strong wind shear.  Late Sunday night, when I saw the Vortex message from the Hurricane Hunters, I noted that it was showing a rise in pressure and an open section of the eyewall and suggested that perhaps it was already beginning its demise even though the winds had increased to 105 mph.  By late Monday afternoon, Hurricane Ida was no longer and Tropical Storm Ida was back with us as winds had dropped to 70 mph, though observations showed a small area of hurricane force winds that the boys that the National Hurricane Center determined was a local anomaly and not indicative of the circulation.  The shear had become so pronounced that early afternoon observations from the Hurricane Hunter indicated that the center at 700 mb was already shifting away from the center at the surface, indicating that the shear was really ripping up the integrity of the structure.

IDAtrack

Tropical Storm Ida Forecast Track (click for most recent)

By late afternoon/evening, Ida was located 40 miles ESE of the mouth of the Mississippi River and 125 miles South of Mobile and was moving north at 17 mph.  Much of the convection was on the north and east side of the storm, again indicative of a storm getting ripped up and perhaps transitioning to an extra-tropical cyclone.  The 00Z Tuesday Tropical Storm Spaghetti Model had more than half of the tracks now not looping back but instead are following a track that I had advocated for several days, which would be from Pensacola to Savannah, GA.  It looks like a Mobile Bay landfall,  50 miles west of Pensacola will be likely.  One thing that I did get wrong, unless it really slows down, is that I had thought that the NAM solution of a day ago of a landfall around 00Z Tue was all wrong and I liked somewhere around midday on Tuesday.  It seems more likely that an early morning landfall is in the cards, provided  that it doesn’t slow down too much and I just think with the shear increasing ahead of a trof coming across the Gulf ahead of a cold front will keep it moving along.   I also think that if the front can keep its legs, it will come and pick it up and take the remnant something north of east and I think that a lot of the models are picking up on that same line of thinking.

latest72hrs

Atlantic Total Precipitable Water Loop (click image for most recent)

All in all, this will be a storm that will bring a minimal storm surge with some gusty winds.  I noted a buoy about 40 miles south of Orange, Alabama with winds of about 35 kts gusting to near 45 kts and seas were running about 16 ft.  The biggest issue with this will be rain, especially for areas well east of the landfall point.  Even though I would think that Ida will be off the Atlantic Coast by Thursday, I would think that an area from say Tallahassee to Savannah to Daytona and maybe as far south as Cedar Key will have 36 to 48 hours of decent rain that could accumulate and cause some problems.  The 10PM EST advisory has Tropical Storm Ida with maximum winds of 65 mph.  The central pressure is 997 mb.  24 hours ago, it was 979 mb and 105 mph winds.  So, it has weakened substantially.  Ida was located about 100 miles SSW of Mobile and had slowed a bit with a northerly track of 13 mph.  It is expected to turn NNE overnight.  At this speed, landfall would be at about 6 am EST Tuesday morning.  See discussion below the Tropical Storm Ida Spaghetti model 00Z Tue.

Ida Spaghetti

Tropical Storm Ida Spaghetti Model (click for most recent)

WTNT41 KNHC 100300
TCDAT1
TROPICAL STORM IDA DISCUSSION NUMBER  25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
900 PM CST MON NOV 09 2009

RADAR AND SATELLITE IMAGES SHOW THE CONVECTION THAT WAS NEAR THE
CENTER DURING THE AFTERNOON HAS WEAKENED AND SHEARED OFF TOWARD THE
NORTH.  THIS WAS CONFIRMED BY A RECENT AIRCRAFT FIX THAT POSITIONED
THE CENTER EAST OF SOUTHEASTERN LOUISIANA WELL SOUTH OF THE
REMAINING DEEP CONVECTION.  THE FORWARD SPEED OF IDA HAS SLOWED TO
ABOUT 11 KT.  THE DYNAMICAL MODEL GUIDANCE FORECASTS A CONTINUED
REDUCTION IN THE FORWARD MOTION OF THE STORM AND A TURN TOWARD THE
EAST AFTER LANDFALL.  THE NHC FORECAST IS CLOSE TO THE PREVIOUS
ADVISORY THROUGH 12 HOURS AND IS THEN ADJUSTED A LITTLE NORTHWARD
CLOSER TO THE MODEL CONSENSUS.

THE AIRCRAFT HAS RECENTLY MEASURED A PEAK 850 MB FLIGHT-LEVEL WIND
OF 71 KT AND A SMFR SURFACE WIND OF 51 KT.  THIS SUPPORTS AN
INITIAL INTENSITY OF 55 KT.  IDA SHOULD GRADUALLY WEAKEN THROUGH
LANDFALL DUE TO INCREASING SHEAR AND COOLER SSTS.  ONCE INLAND THE
CYCLONE WILL WEAKEN AT A FASTER RATE AND BECOME EXTRATROPICAL
SHORTLY THEREAFTER.  MOST OF THE GLOBAL MODELS SHOW THE CYCLONE
BEING ABSORBED BY A FRONTAL BOUNDARY IN 36-48 HOURS AND SO DOES THE
OFFICIAL FORECAST.

THE LOCATION AND TIMING OF IDA’S LANDFALL WILL HAVE LITTLE
SIGNIFICANCE SINCE THE TROPICAL STORM FORCE WINDS COVER A LARGE
AREA AND MOST OF THE HEAVIER RAINFALL IS ALREADY SPREADING ONSHORE.

FORECAST POSITIONS AND MAX WINDS

INITIAL      10/0300Z 29.3N  88.6W    55 KT
12HR VT     10/1200Z 30.8N  87.9W    40 KT…EXTRATROPICAL
24HR VT     11/0000Z 31.5N  86.5W    30 KT…EXTRATROPICAL
36HR VT     11/1200Z 31.3N  84.8W    25 KT…EXTRATROPICAL
48HR VT     12/0000Z…DISSIPATED

$$
FORECASTER BROWN/BERG

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