000
WTPZ43 KNHC 312036
TCDEP3
 
Tropical Storm Hilda Discussion Number   5
NWS National Hurricane Center Miami FL       EP082021
200 PM PDT Sat Jul 31 2021
 
After strengthening quickly overnight and early this morning,
Hilda's intensity appears to have leveled off for now.  There
continues to be hints of an eye feature in satellite images and
deep convection is organized in curved bands around that feature.
The latest Dvorak estimates are 3.5/55 kt from TAFB, 4.0/65 kt from
SAB, and 4.1/67 kt from CIMSS at the University of Wisconsin.  A
recent ASCAT-B overpass showed a maximum wind of around 50 kt
southeast of the center, but the coarse resolution of the
instrument is unlikely to capture the storm's true intensity.
Based on a combination of this data, the initial intensity is held
at 60 kt, but this could be a little conservative and Hilda is very
near hurricane strength.  The aforementioned ASCAT data was also
used to adjust the wind radii inward at the initial and short range
forecast times.
 
Steady strengthening seems likely during the next 24 to 36 hours as
the environment remains generally favorable, consisting of
relatively warm SSTs, low wind shear, and a high amount of
moisture.  The NHC intensity forecast during that time period is
the same as before and lies at the high end of the model guidance,
near HCCA.  Beyond 36 hours, however, decreasing moisture and
progressively cooler SSTs should end the strengthening trend and
gradually cause weakening during the remainder of the forecast
period.  The NHC intensity forecast lies near the middle of the
guidance envelope for that portion of the forecast.
 
Hilda is moving west-northwestward at 12 kt.  A subtropical ridge
should keep the storm on a general west-northwest heading during the
next several days, but the more skillful models like the GFS and
ECMWF show some interaction with Tropical Depression Nine-E to
the west and a low pressure area to the east.  These interactions
will likely cause some slow downs and an erratic motion at
times during the forecast period.  There continues to be a fair
amount of spread in the models, especially in terms of forward
speed, and the new forecast is a little to the north of the
previous based on the latest guidance.  This track prediction is
slightly slower than the consensus aids, and has given more weight
to the GFS and ECMWF models.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/2100Z 14.1N 117.9W   60 KT  70 MPH
 12H  01/0600Z 14.5N 119.3W   70 KT  80 MPH
 24H  01/1800Z 15.0N 121.0W   80 KT  90 MPH
 36H  02/0600Z 15.5N 122.5W   85 KT 100 MPH
 48H  02/1800Z 16.0N 123.8W   80 KT  90 MPH
 60H  03/0600Z 16.8N 125.1W   75 KT  85 MPH
 72H  03/1800Z 17.8N 126.7W   65 KT  75 MPH
 96H  04/1800Z 19.3N 129.8W   50 KT  60 MPH
120H  05/1800Z 20.4N 133.7W   40 KT  45 MPH
 
$$
Forecaster Cangialosi