11:00 A.M. EDT UPDATE OF INFORMATION ON TROPICAL STORM KAREN..PLEASE REVIEW THE FOLLOWING FORECAST DISCUSSION FROM THE NHC:
NHC FORECAST DISCUSSION LINK
Good morning everyone!
Tropical Storm Karen has weakened overnight, due mainly to 20-25 knots of wind shear allowing the LLC to become exposed to the west of the heavy convection. As of the 8:00 a.m. EDT Intermediate Advisory from the NHC, the following information was posted. Please note, the tracking map does not update on the intermediate advisories, so the tracking map contains the 5:00 a.m. EDT information.
7:00 AM CDT Fri Oct 4
Location: 25.2°N 90.0°W
Moving: NNW at 10 mph
Min pressure: 1003 mb
Max sustained: 60 mph
Analysis of satellite loop imagery this morning clearly shows the LLC of Karen exposed to the west of the convection associated with the storm. However, even with dry air ahead, and with the storm being “tilted”, she has held her current maximum wind speed of 60 mph. the last few frames of the loop seem to indicate convection is trying to develop close to the center of circulation. Whether this is temporary, or sign of a strengthening trend, remains to be seen.
Currently, the storm is under about 15-20 knots of wind shear, and the shear tendency map indicates wind shear values have been decreasing over the past 24 hours. This may allow for convection to remain closer to the center of circulation. The map also indicates Karen is heading for an area of lesser wind shear at the moment, and toward an area where mid shear is only on the order of 5 knots at the most. The accuracy of these maps will I guess be determined if we see Karen start to become better organized or not.
The current wind shear and zonal shear forecast from the GFS indicates upper level winds, or wind shear values to remain marginal in around the range we see at the moment, with wind shear increasing prior to Karen making landfall. It is noted however, the NHC has mentioned in there 5:00 a.m. discussion the probability of what I pointed out yesterday, in that a very small window of opportunity may exist for her to intensify close to hurricane strength. I have this area pointed out in the zonal shear map, where a very small core (which should correlate to where the center of Karen may be at that time) of upper level winds, where the shear drops to almost zero. This could be enough for her to intensify as thought by the NHC. Based on the length of exposure of the LLC we have seen, even if Karen can intensify, due to the surrounding dry air, chances for her attaining hurricane status are pretty slim, however she will need to be watched in the event of any unforeseen changes. From the NHC 5:00 a.m. discussion:
THE INTENSITY FORECAST IS RATHER PROBLEMATIC. FIRST…KAREN IS LIKELY TO INTERACT WITH A SMALL UPPER-LEVEL TROUGH DURING THE NEXT 24 HOURS…WHICH MIGHT PROVIDE SOME SUPPORT FOR RENEWED CONVECTION. SECOND…THE SHEAR MAY DIMINISH IN THE WAKE OF THE TROUGH…WHICH COULD ALLOW FOR INTENSIFICATION…ESPECIALLY IF KAREN TURNS NORTHEASTWARD WHILE STILL OVER WATER. THE ECMWF SHOWS ABOUT 10 MB OF DEEPENING AFTER RECURVATURE…AND THE GFS…HWRF…AND GFDL MODELS SHOW MORE. BASED ON THESE MODELS AND CURRENT TRENDS…THE INTENSITY FORECAST IS MODIFIED TO SHOW LITTLE CHANGE IN STRENGTH THROUGH 24 HOURS…FOLLOWED BY INTENSIFICATION TO NEAR HURRICANE STRENGTH BY 48 HOURS. AFTER LANDFALL…KAREN SHOULD WEAKEN AND EVENTUALLY BECOME EXTRATROPICAL AS IT MERGES WITH THE DEEP-LAYER TROUGH.
Based on the update current steering layer mean map, and forecast steering layers maps valid for 12Z, I expect Karen to continue the NNW motion for the remainder of the morning, and the the front/trof approaching closer today, I would almost expect a slowing in forward motion, and look for turn more toward the north later today, to early evening.
Based on the forecast steering maps, and current water vapor satellite loop imagery beginning to show a change in flow, I pretty much concur with the NHC forecast track and 12Z Dynamic model guidance, however I do prefer the track of the TVCA / TVCN / TVCC consensus models.
Albeit she may never reach hurricane status, a HURRICANE WATCH is still in effect from the eastern LA coastal area, to the western FL. Panhandle. Residents in these areas are urged not to take this lightly.
The following Storm Surge values have been issued by the NHC, and the posted SLOSH map indicates what could be experienced as Karen makes landfall. Given she is an eastern weighted system, the worse effects will be felt where the center makes landfall, and to the east of the center.
NHC STORM SURGE VALUES
STORM SURGE…THE COMBINATION OF STORM SURGE AND THE TIDE WILL CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING WATERS.
THE WATER COULD REACH THE FOLLOWING HEIGHTS ABOVE GROUND IF THE PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE…
WEST OF THE MISSISSIPPI RIVER TO TERREBONNE BAY…1 TO 3 FT
MOUTH OF THE MISSISSIPPI RIVER TO MOBILE BAY…3 TO 5 FT
EAST OF MOBILE BAY TO WEST OF APALACHEE BAY…1 TO 3 FT
APALACHEE BAY…2 TO 4 FT
SOUTH OF APALACHEE BAY TO TAMPA BAY…1 TO 2 FT
SLOSH MODEL OUTPUT
Residents in the HURRICANE WATCH area, and Tropical Storm WARNING area should remain away from the coast, as these areas will likely experience minor coastal flooding and beach erosion, along with heavy wind and rain near and east of the center. Also, rip currents WILL BE PRESENT, and the threat for tornadoes does exists.
Residents under the WARING and Watch areas should monitor NOAA Weather Radio, and Local NWS Statements and warnings for actions to be implemented. Questions should be directed to your local emergency management office.
ALL satellite images, and graphics are linked for you to get a closer look at information, and links are provide for you to click on for NWS information.
I will have another update this evening, and I will be on this weekend along with Doppler Radar images and loops.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)