See latest on Cat 2 Hurricane Ida in Gulf with Cancun Radar image, sea surface temperature, satellite image, forecast track CLICK HERE
Tropical Storm Ida is behaving itself though it looks to be in pretty good shape. As noted yesterday, as the storm came offshore, the convection in the center exploded and the intensity was raised to 60 kts and there was some thought that perhaps it may become a hurricane by nightfall. But, a little southerly shearing came into play and the late night advisory kept the storm at 60 kts. Ida appears as if it will more or less thread the needle through the Yucatan channel thus keeping its center of circulation over water between the Island of Youth in Cuba and Cozumel near the top of the Yucatan Peninsula. As mentioned previously, the satellite image if fairly impressive and there are strong winds aloft to the north of the storm. The official forecast reflects the potential for some good outflow that may provide for an uptick in the intensity to that of low end Hurricane status. I won’t be surprised to see it go higher than the current forecast of 70 kts. That same shear, however, will then serve to mess up the storm and so the forecast calls for it to fall back to tropical storm status. Confidence is pretty high through Monday. (see discussion below)
After that, a cold front comes down into the Gulf. Now, yesterday I opined that the then forecast of it turning back southeast seemed a bit improbable to me. I thought a conventional viewpoint of the storm getting caught up in the strong southwesterly flow ahead of the trof, thus shooting the storm northeast, would be something to consider. Only two of the models though played out that scenario and the hurricane center went with the consensus of the modeling data. However, later model runs have taken the storm farther north, then north northeast toward the Florida Panhandle. In doing so, the storm is expected to be so influenced by the front and colder water over the northern Gulf (we’ve had a lot of strong cold fronts lately) that Ida becomes Extra-Tropical. The official forecast then turns the storm southeast as the thinking is that it gets absorbed by the front and moves with the front to the southeast. I know the models say that but several go ahead and take the remnant of Ida into the extreme southeastern US.
I contend that solution is still something that should be considered given that the low will have forward momentum and also there will be those strong southwesterly winds. I mean, a conventional low moves up along a front with a strong flow and I’m not so sure that an extra-tropical cyclone is just going to get absorbed into nothing and, if it were, then there would be no center of circulation to track. Seems to me that if it is still a distinct circulation center, it would run up the front. Now, its true, the models do take the storm back south, but I contend that climatology and the fact that the storm is transitioning from a tropical system that is may be possible that the models are confused. In any event, its an interesting academic discussion. As it stands, regardless, winds will get pretty gusty in the Florida panhandle. I suspect that there will be pretty heavy rain along that front too, given the amount of moisture being drawn northward. With the increase in convection with a disturbance coming from the Bay of Campeche, I would think that anywhere from New Orleans to Tallahassee will get a pretty good dose of rain.
WTNT41 KNHC 080246
TROPICAL STORM IDA DISCUSSION NUMBER 15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009
1000 PM EST SAT NOV 07 2009
THERE HAS BEEN LITTLE CHANGE TO THE SATELLITE APPEARANCE OF IDA
SINCE THE AIR FORCE PLANE LEFT EARLIER THIS AFTERNOON. THE
LOW-LEVEL CENTER IS STILL EMBEDDED WITHIN A LARGE CENTRAL DENSE
OVERCAST ALTHOUGH RECENT MICROWAVE DATA SUGGEST THAT THE SYSTEM IS
BEING IMPACTED BY SOME SOUTHERLY SHEAR. THE INTENSITY WILL BE HELD
AT 60 KT FOR THIS ADVISORY…WHICH IS SUPPORTED BY DVORAK ESTIMATES
OF 55 KT FROM BOTH TAFB AND SAB AND AN OBJECTIVE ADT ESTIMATE OF 61
KT. ANOTHER AIR FORCE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO
INVESTIGATE IDA IN A FEW HOURS TO PROVIDE UPDATED INFORMATION.
IDA HAS TURNED TO THE NORTH-NORTHWEST WITH AN INITIAL MOTION OF 340
DEGREES AT 10 KT AS IT IS STEERED BETWEEN AN AMPLIFIED TROUGH OVER
MEXICO AND A MID-LEVEL RIDGE THAT EXTENDS FROM THE SOUTHEASTERN
U.S. TO HISPANIOLA. THE TRACK GUIDANCE IS IN EXCELLENT AGREEMENT
THROUGH 48 HOURS ON A CONTINUED NORTH-NORTHWESTWARD MOTION…AND
THE NEW OFFICIAL FORECAST IS ONLY SLIGHTLY TO THE EAST OF THE
PREVIOUS FORECAST. THEREAFTER…ALL THE MODELS BRING IDA TO THE
COAST NEAR THE FLORIDA PANHANDLE AS AN EXTRATROPICAL CYCLONE BUT
QUICKLY TURN IT TO THE SOUTHEAST AS THE ABSORBING COLD FRONT
PUSHES SOUTHWARD OVER THE GULF.
ALTHOUGH SOME SHEAR IS AFFECTING IDA…IT IS NOT PROHIBITIVELY
STRONG. STRONG UPPER-LEVEL WINDS NORTH OF THE SYSTEM ARE PROVIDING
SOME DIFFLUENCE ALOFT…AND THIS WILL CONTINUE TO GIVE IDA A 24-36
HOUR WINDOW TO STRENGTHEN TO A HURRICANE. THE SHEAR IS EXPECTED TO
INCREASE AFTER 36 HOURS AND SHOULD LEAD TO SOME WEAKENING…BUT THE
NEW INTENSITY GUIDANCE INDICATES THAT THIS WEAKENING COULD BE
SLOWER TO OCCUR THAN PREVIOUSLY FORECAST. IDA SHOULD BEGIN THE
EXTRATROPICAL TRANSITION PROCESS AROUND 48 HOURS AND BE FULLY
EXTRATROPICAL BY 72 HOURS.
A TIGHT PRESSURE GRADIENT BETWEEN IDA AND HIGH PRESSURE LOCATED OVER
THE SOUTHEASTERN UNITED STATES IS ALREADY PRODUCING STRONG WINDS
OVER THE SOUTHEASTERN GULF OF MEXICO…BUT THESE WINDS ARE NOT
DIRECTLY ATTRIBUTABLE TO THE CIRCULATION OF IDA.
FORECAST POSITIONS AND MAX WINDS
INITIAL 08/0300Z 20.1N 84.6W 60 KT
12HR VT 08/1200Z 21.2N 85.3W 70 KT
24HR VT 09/0000Z 23.0N 86.5W 70 KT
36HR VT 09/1200Z 25.4N 87.6W 65 KT
48HR VT 10/0000Z 27.7N 87.9W 60 KT
72HR VT 11/0000Z 30.0N 86.5W 45 KT…EXTRATROPICAL
96HR VT 12/0000Z 29.0N 85.5W 35 KT…EXTRATROPICAL
120HR VT 13/0000Z…ABSORBED BY FRONT