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HURRICANE DANNY DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042015
1100 PM AST THU AUG 20 2015

Danny continues to produce a compact central dense overcast, and
cloud tops are a little colder than earlier due to a recent burst of
convection in the eyewall.  Coincidentally, the convective canopy
has intermittently been obscuring the tiny eye that was observed
earlier today.  The initial intensity remains 70 kt based on a blend
of subjective Dvorak satellite estimates of T4.0/65 kt from TAFB and
T4.5/77 kt from SAB.

The hurricane continues to move west-northwestward, or 295/9 kt,
toward a break in the subtropical ridge located northeast of the
Leeward Islands.  The track guidance shows this motion continuing
for another 36 hours, with Danny then turning westward and
accelerating from 48 hours through day 5 while the ridge builds
westward north of the Greater Antilles.  With the exception of the
GFDL, GFDN, and NAVGEM--which insist that Danny will turn
northwestward before reaching the Leeward Islands--the other track
models are in agreement on a future track near or just south of the
northern Leeward Islands and Greater Antilles.  This clustering of
the guidance required no significant changes to the official NHC
track forecast on this advisory cycle.

As has been mentioned in earlier discussions, Danny is susceptible
to sudden and possibly unexpected changes in intensity due to its
small size.  Since vertical shear is expected to remain low for
another 24 hours or so, Danny could certainly strengthen some more
if it can avoid intrusions of dry air into the inner core.  After
36 hours, an increase in westerly to southwesterly shear and a
decrease in mid-level relative humidities are expected to lead to
weakening, and Danny is forecast to weaken to a tropical storm
before it reaches the Leeward Islands.  The updated NHC intensity
forecast is very similar to the previous one and remains close to
the IVCN consensus.  It should be noted that given Danny's small
size, the weakening rate after 36 hours could be faster than
indicated in the official forecast.

A NOAA aircraft will be conducting a research mission in and around
Danny Friday afternoon, and an Air Force Reserve Unit reconnaissance
aircraft will investigate Danny Saturday afternoon.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 13.4N  46.6W   70 KT  80 MPH
 12H  21/1200Z 14.0N  47.9W   75 KT  85 MPH
 24H  22/0000Z 14.7N  49.8W   75 KT  85 MPH
 36H  22/1200Z 15.2N  51.9W   70 KT  80 MPH
 48H  23/0000Z 15.6N  54.2W   60 KT  70 MPH
 72H  24/0000Z 16.5N  59.3W   55 KT  65 MPH
 96H  25/0000Z 17.5N  64.5W   50 KT  60 MPH
120H  26/0000Z 18.0N  69.5W   45 KT  50 MPH

$$
Forecaster Berg

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