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By: wxchaser97 , 1:14 AM GMT on October 05, 2013
Tropical Storm Karen
Since this is the 2013 Hurricane Season, Karen remains disorganized. The center remains on the western edge of the convection. While convection tries to refire over Karen's center, it is getting sheared away. This is what happens when you have moderate shear impacting a tropical cyclone with no ULAC over the tropical system. This wind shear has also caused Karen to become decoupled somewhat. This means that the low-level center and the mid-level centers are not vertically aligned, which isn't good for the prospects of intensification. This decoupling is noticeable on CIMSS vorticity maps and microwave imagery. The dry mid-upper levels of the atmosphere aren't helping Karen's cause either. The dry air has been suppressing convection on mostly the western side of Karen. Nevertheless, Karen still has a well-defined low-level circulation. Aircraft reconnaissance flights show Karen having maximum sustained surface winds of about 50mph and a central pressure of 1003mb. TAFB and SAB T#'s also support surface winds up to 50mph. The latest advisory information, satellite image, and microwave image can be found below.
7:00 PM CDT Fri Oct 4
Location: 25.9°N 90.3°W
Min pressure: 1002 mb
Max sustained: 50 mph
Forecast For TS Karen
Tropical Storm Karen won't get as strong as forecast earlier. Moderate wind shear and a dry central GOM have been able to keep Karen at bay. If fact, these unfavorable conditions have been able to weaken Karen as she gets farther north. Luckily for the people along the Gulf Coast, conditions don't look to get favorable for significant intensification. This doesn't mean that Karen couldn't slightly strengthen, but significant intensifying is unexpected. Global models and SHIPS analysis continue to show moderate wind shear over Karen and issues with dry air. Karen is also moving over an area with less TCHP values which means there is a little less energy available for the cyclone. Based on this, it looks like Karen will only be able to maintain strength, at the most, for the next 24hrs. As Karen nears landfall, increased upper level divergence should move over Karen ahead of the approaching trough. This could promote some convective growth and consequently some intensification. Global models are also in decent agreement that there may be some strengthening before landfall. After making landfall, conditions turn very unfavorable for Karen. Besides having its heat source lost, wind shear will sharply increase due to the aforementioned trough. This should, along with the baroclinic energy getting injected into Karen, turn her into a post-tropical storm before getting absorbed into the trough. My forecast shows for the maintained intensity of 45kts for the next 36hrs before slightly increasing to 50kts. It is entirely possible that Karen doesn't strengthen at all and even continue to slowly weaken before making landfall. This is especially true if the system fully decouples and makes a quicker landfall. Also if Karen fully decouples and the low-level circulation stays exposed, then there is a small possibility that Karen degenerates.
Karen has slowed a little from yesterday and is generally moving to the NNW. The center has made some wobbles due to the fluctuations of the convection. Karen is still riding around the periphery of the subtropical ridge to the west. As Karen has remained weaker than previously thought, the ridge has been able to push Karen a little farther west. As the mid to upper level trough gets closer, Karen will feel more of the effects of this trough. Karen has already slowed its forward motion and turned a little farther north than from yesterday and these effects will increase over the next day. As we get past about 24hrs, we should see Karen get turned to the NE and begin to accelerate. The trough will then continue to pull Karen to the NE over the SE US before getting absorbed in about 4 days. Global models have come into a little better agreement in the track of Karen, but there is still differences in timing and how far east/west Karen will get between the GFS and ECMWF. knowing that the ECMWF has done better with Karen, and the fact that the GFS shows a sharper turn, I am more inclined to go with a solution near the Euro. The dynamical/statistical guidance is spread still from LA to FL. Based on all of this, a track into the far western FL panhandle seems likely in about 48-60hrs. Karen should bring gusty winds, moderate rain, and a few tornadoes to the NE Gulf Coast over the weekend. Some minor coastal flooding is also possible due to the increased wave heights and storm surge. This won't be a huge impact storm, but people in Karen's path still need to be prepared for TS conditions.
INIT 04/0000Z 45 KT 50 MPH
12H 05/1200Z 45 KT 50 MPH
24H 06/0000Z 45 KT 50 MPH
36H 06/1200Z 45 KT 50 MPH
48H 07/0000Z 50 KT 60 MPH
72H 08/0000Z 30 KT 35 MPH...POST-TROP/EXTRATROP
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* MORGAN CITY LOUISIANA TO THE MOUTH OF THE PEARL RIVER
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* METROPOLITAN NEW ORLEANS
* LAKE MAUREPAS
* LAKE PONTCHARTRAIN
* EAST OF THE MOUTH OF THE PEARL RIVER TO INDIAN PASS FLORIDA
A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.
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