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"Karen" Trying to Hang On

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Updated: 10/05/2013 8:37 am
Weak "Karen" Into the Northern Gulf....... 

FOR THE FIRST COAST: (our weather (forecast/effects) changes very little even if "Karen" dissipates due to a plume of tropical moisture moving into the area + an approaching cold front)

** given the forecast thinking/reasoning (as discussed below), local impacts will -- generally -- be pretty minor

** Sat. will be nice....showers & a few t'storms will develop Sunday through Sun. night, but not anywhere close to washout with only some brief heavy rain in some spots.

** an isolated threat for tornadoes favoring western parts of the viewing area (Lake City to Waycross) but at least some threat for Jacksonville & the rest of NE Fl., SE Ga. Monday given the combination of Karen's remnants, a cold front, a strong upper level trough + some surface heating.

** some heavy rain but speed of the system (not to mention weak overall intensity) + a track to the west/northwest of Jax should limit the overall amounts -- perhaps an average of a half inch to an inch, locally 1-2" especially west & northwest of Jax. 

** breezy Sunday through Mon. but not overly strong averaging 15-25 mph.

** somewhat rough seas & surf Sunday-Mon. but again relatively minor.  An offshore component to the winds by later Mon.-Tue. will make for happy surfers(!).

Infrared satellite below shows strong convection way to the east of the center.

The visible satellite below nicely shows the center of the circulation far removed (to the west/northwest) from the intense convection.

While there has been -- & will be -- bursts of convection, it's questionable as to whether or not the center can ever truly become imbedded underneath the strong convection thereby allowing the mid level & low level center to become stacked.  A stacked system would be at much higher risk of intensifying.  This kind of development is unlikely.

Sea surface analysis below.  The numbers show the wave heights with the highest numbers closer to "Karen", of course.  Higher waves/rough seas & surf & a high rip current risk will affect the Fl. Panhandle coast through the weekend.  Wave heights will not be significant for the First Coast.

Satellite imagery shows a struggling "Karen" thanks to a continuation of moderate west/southwest shear.  The center is clearly displaced to the west of the strong convection as mentioned above.  The track has generally been a little west of earlier forecasts, but the end results should be similar to previous expectations.  I question -- actually doubt -- whether or not "Karen" will be able to truly reorganize & strengthen given its current poorly organized state & the decoupled centers.

The storm continues to be essentially decapitated by persistent west/southwest shear of 20+ knots.  The question becomes whether or not the storm can reorganize given the messy appearance on satellite imagery + the relatively short time over warm water Sat.-early Sun. before landfall. Water temps. are more than warm enough to support a tropical cyclone, but the shear as well as dry air will be something "Karen" will have to battle throughout the weekend.  Some organization is possible upon approach to the coast due to interaction with a cold front & approaching upper level trough.  The primary intensity issues: 

(1) very dry mid & upper level air (as can be seen on the water vapor images below - the black & rust color) over Mexico & virtually all of the western half of the Gulf of Mexico extending north into the Southern U.S.  This dry air may ultimately be the most significant hurdle for "Karen" to overcome as the dry air will remain adjacent to the storm all the way through landfall.

(2) the moderate to quite strong shear over the Gulf will abate some through Sat. night - Sun. before increasing again Sun. night-Mon. as an upper level trough approaches.  

In addition... as the upper level trough moves into the Eastern U.S., there might be some "ventilation" (diffluent flow aloft) of "Karen" upon approach to the Gulf Coast which could compensate for the increasing shear & dry air, thereby at least maintaining the storm or even allowing for some increase of the convection near the center.  It will not take long for "Karen" to transition to an extratropical low pressure area moving northeast along the cold front Mon. & Tue.

The timing & how far south this upper trough digs will be the main driver for the track of "Karen".  A weak & transient upper level ridge will build north & northeast of the storm through Sat. night over Georgia & Northeast Fl.  As the trough approaches, the ridge will collapse paving the way for the northeast acceleration of "Karen" Sun. night-Mon.  The system will then become attached to a cold front & absorbed by the upper trough over the Eastern U.S.  The timing -- landfall -- of "Karen" has generally slowed which is no surprise since the upper level trough is strong & still deepening, a process that should be completed by Sunday.  In such a scenario, a slower evolution of weather systems usually evolves until the trough has completed the deepening process thereby slowing the "hook up"/merge of "Karen" with the cold front.

Atmospheric data gathered by hurricane hunter aircraft + research planes have been inputted into the forecast models since Thu. night & seems to have allowed for some model consistency. Interestingly....according to the NHC after using radar imagery for the HWRF model:
... "DATA FROM THE FROM THE NOAA P-3 TAIL DOPPLER RADAR. THIS MARKS THE FIRST TIME 
DOPPLER RADAR DATA HAVE BEEN ASSIMILATIED INTO AN OPERATIONAL HURRICANE
 MODEL
IN REAL TIME"
....
Virtually all global forecast models are now keeping "Karen" weaker with a move very near the southeast tip of Louisiana overnight Sat./early Sun. then a final landfall (if the center survives!) from Mobile to Panama City or so Sun. night.  

So....  I favor "Karen" moving to the Gulf Coast somewhere between approximately Pascagoula & Apalachicola about Sunday night.  The trend more west & north of the center that's void of convection has been due to the shallow nature of the storm, & it's not entirely out of the question that the center -- a swirl of low level clouds -- could move north into Louisiana & essentially dissipate there. 

If traveling this weekend west to the Fl. Panhandle &/or coastal Mississippi/Alabama, stay up to date on "Karen".  Heavy rain & gusty winds....& possibly isolated tornadoes.... will be most significant from about the Fl. Big Bend across the Panhandle to as far west as near Pascagoula, but this will not be a major tropical cyclone for the Gulf Coast.  There will also be a corridor of potentially enhanced heavy rain & isolated tornadoes across Georgia into the Carolina's near & just east & south of the track of "Karen" or its remnants Sun.night-Monday in tandem with the advancing cold front & a strong upper level disturbance.

Click ** here ** for buoy reports from the Gulf of Mexico.

The image below shows the moderate -- 20(+) knots -- over a good portion of the Gulf of Mexico.

Water vapor satellite images below showing the vast area of very dry air in close proximity to "Karen":

Model plots + radar imagery (with projected track of "Karen") below courtesy S. Fl. Water Management District:


The satellite imagery below shows the maturing powerful upper level storm system over the Central U.S. that's driving a cold front eastward (note t'storms north-south along a cold front) which will eventually pull "Karen" -- or its remnants -- northward.

Tropical waves continue to decrease as they move off the coast of Africa. This late in the season, development -- or at least long track tropical cyclones across the Atlantic -- is not common so deep in the tropics.  Still...these waves would have at least some potential for long term development if they can get across the Atlantic near the Caribbean &/or SW Atlantic.  There are indications of long term development in or near the Caribbean & SW Atlantic in roughly 10 days to 2 weeks.

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