Good evening all!
Tropical Storm Karen has weakened over the past 12 hours, and the LLC remains exposed to the west of the heavy convection due to some westerly to WSW wind shear. The forecast for the wind shear was for it to relax enough to allow convection to remain closer to the center, based on the previous 3 days runs of the GFS shear forecast. However, based on information contained in the NHC forecast discussion text, shear had been underestimated, as data from a NOAA-G IV flight flying a surveillance mission revealed shear was stronger than originally thought…therefore, Karen remains decoupled. The storm has become almost stationary, and may resume a brief NNW motion, before turning to the NE. The following information as of the 8:00 p.m. EDT Intermediate advisory from them NHC, and is contained in the tracking map. Please note…the map graphic is only updated with the 5:oo p.m. data.
GLOBAL TRACKS 7 KAREN TRACKING MAP
Based on the shear and dry air still in place, it wouldn’t surprise me to see Karen weaken further. Based on the current wind shear forecast still, as the storm begins to move toward the NE, and passes the LA eastern coastal area, models indicate wind shear could possibly relax, as discussed in the 5:00 p.m. NHC forecast discussion, and some slight strengthening could occur before a second landfall int he FL. Panhandle. So, right now, I have two scenarios for you at the moment…should wind shear keep steady and not relax, there is the chance the LLC may continue northward, separated from the convection, and could possibly dissipate. On the other hand, should the wind shear relax for the brief moment prior to the FL. Panhandle, the strengthening per the NHC could occur. Based on this, I will be on in the morning to continue monitoring the situation.
In light of the weakening trend, the NHC discontinued the HURRICANE WATCH earlier today, and that portion of the update was posted earlier, in that the NHC may in fact cancel the HURRICANE WATCH. I can truly empathize for those folks who began preparations, as I have personally been in that situation myself, only to have the storm turn away less than 12 hours from landfall.
As far as forecast track, I have to go with the current NHC track, as the 00Z dynamic model track guidance is now showing a sharper turn to the right, just barely clipping LA. and coming a little further east as far as landfall in the FL. Panhandle, however not by much. This could be due to the decoupled center, as far as the shift in the model guidance.
In any case, the NHC still expects the same storm surge values over the same locations, and the following SLOSH data provides a close approximation of these values. SLOSH data accuracy is plus or minus 20% of the values flagged.
Residents in the Watch and Warning areas need to monitor NOAA Weather Radio, and local NWS Office statements closely.
NWS LOCAL STATEMENTS LINK
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)