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Tropical Storm Hilda Discussion Number   2
NWS National Hurricane Center Miami FL       EP082021
900 PM MDT Fri Jul 30 2021
 
Satellite imagery indicates that Hilda has gotten a little better 
organized during the past several hours, with the low-level
center now near the eastern end of a long convective band that is
present in the southwestern semicircle.  Satellite intensity
estimates are 35 kt from TAFB and 45 kt from SAB, and based on
these the initial intensity remains 40 kt.  The storm is currently
in an environment of light northwesterly vertical wind shear with
the bulk of the outflow to the south.
 
Conditions generally appear favorable for strengthening during the
next 72 h or so, as Hilda is expected to be over warm sea surface
temperatures and in an environment of light to moderate shear.
Based on this, the first part of the intensity forecast is unchanged
from the previous forecast and calls for Hilda to become a
hurricane between 24 and 36 h and peak in intensity around 60 h.
After that, the forecast becomes less confident.  The cyclone is
expected to move over decreasing sea surface temperatures after 
72 h, and this should cause gradual weakening as indicated in the
official forecast.  The official forecast for this period has been 
nudged downward due to the forecast motion over cooler water.  
However, the GFS and ECMWF models suggest the possibility that Hilda 
will interact with other nearby systems - the GFS forecasting with 
Tropical Depression Nine-E to the west and the ECMWF forecasting 
interaction with a disturbance to the east.  Should either of these 
interactions occur, Hilda could weaken at a different rate than 
currently forecast.
 
The initial motion is 290/13.  Hilda is located on the south side 
of a subtropical ridge, and if the storm does not interact with 
other nearby weather systems a general west-northwestward motion 
with a decrease in forward speed is expected through the forecast 
period.  The new forecast track is shifted a little north of the 
previous track, and it lies just to the south of the various 
consensus models.  If Hilda does interact with either Tropical 
Depression Nine-E or the disturbance to the east, it will lead to 
erratic motion.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 13.2N 114.6W   40 KT  45 MPH
 12H  31/1200Z 13.5N 116.3W   50 KT  60 MPH
 24H  01/0000Z 14.1N 118.4W   60 KT  70 MPH
 36H  01/1200Z 14.7N 120.3W   70 KT  80 MPH
 48H  02/0000Z 15.3N 122.0W   75 KT  85 MPH
 60H  02/1200Z 15.8N 123.3W   75 KT  85 MPH
 72H  03/0000Z 16.5N 124.8W   70 KT  80 MPH
 96H  04/0000Z 18.0N 127.0W   60 KT  70 MPH
120H  05/0000Z 19.5N 131.0W   50 KT  60 MPH
 
$$
Forecaster Beven
 
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