[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 230236
TCDAT4

TROPICAL STORM DANNY DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042015
1100 PM AST SAT AUG 22 2015

Satellite imagery and data from an earlier NOAA Hurricane Hunter
aircraft mission indicate that Danny has continued to quickly
weaken.  The center has become exposed to the southwest of the
remaining deep convection due to moderate southwesterly shear and
dry air.  The earlier SFMR data supported an intensity of 50 to 55
kt around 0000 UTC, and since the organization of Danny has
continued to decrease the advisory intensity has been lowered to
50 kt.  The next NOAA and U.S. Air Force Reserve reconnaissance
missions into Danny are scheduled for 0800 and 1200 UTC,
respectively.

Danny is expected to remain within a hostile environment consisting
of dry mid-level air and moderate to strong southwesterly shear.
This should result in additional weakening.  Due to the fast rate of
weakening Danny experienced today, the new NHC intensity forecast
is significantly lower than the previous advisory, and is in best
agreement with the HWRF and LGEM guidance.  The NHC forecast now
shows Danny weakening to a tropical depression within a couple of
days and dissipating by day 5.  Both of these events could occur
sooner.  In fact, the ECMWF, GFS, and UKMET all show Danny
degenerating into a trough of low pressure by the time it nears
Hispaniola in 2 to 3 days.

Danny appears to have turned westward as anticipated, with an
initial motion estimate of 275/13.  The overall track forecast
philosophy remains unchanged from the previous advisory. The cyclone
should continue on a general westward motion during the next 24 to
36 hours.  After that time, Danny is forecast to turn west-
northwestward to the south of a low-level ridge over the western
Atlantic.  The dynamical models are in relatively good agreement on
this scenario, and the updated NHC track is similar to, but a little
south of, the previous advisory primarily due to the more southward
initial position and current westward motion.

Since Danny has rapidly weakened today and there is a reasonable
possibility that it will be below tropical storm strength while
moving through the Leeward Islands, the governments of the various
islands have elected to maintain tropical storm watches at this
time. Additional watches or warnings could still be required for
portions of the Leeward Islands, the Virgin Islands, and Puerto Rico
on Sunday if Danny does not weaken as quickly as forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  23/0300Z 15.6N  54.7W   50 KT  60 MPH
 12H  23/1200Z 15.9N  56.7W   45 KT  50 MPH
 24H  24/0000Z 16.4N  59.3W   40 KT  45 MPH
 36H  24/1200Z 16.9N  61.9W   35 KT  40 MPH
 48H  25/0000Z 17.7N  64.4W   30 KT  35 MPH
 72H  26/0000Z 19.5N  69.3W   25 KT  30 MPH
 96H  27/0000Z 21.7N  73.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  28/0000Z...DISSIPATED

$$
Forecaster Brown/Berg
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