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Tropical Storm Pilar Discussion Number  14
NWS National Hurricane Center Miami FL       EP192023
1000 PM CDT Tue Oct 31 2023
 
After the previous advisory, a significant convective burst formed 
mainly to the west of the center of Pilar that is now waning. 
While the most recent GPM microwave pass missed the center of 
the storm, it did catch a prominent curved band on the 37-GHz 
channel extending to the northwest away from the center. Subjective 
Dvorak estimates were T3.0/45 kt from TAFB and T3.5/55 kt from SAB. 
Taking a blend of these estimates, the initial intensity is set at 
50 kt this advisory. This value also assumes a bit of undersampling 
from the ASCAT-B/C passes that had peak wind retrievals of 45 kt 
outside of the convection earlier today. While the wind-radii were 
adjusted a bit based on that scatterometer data, the 34-kt winds 
remain just offshore of El Salvador.
 
Pilar has nudged a bit closer to the coast of El Salvador, with the 
estimated motion a drift to the north at 360/2 kt. The upper-level 
trough that had weakened the ridging over Mexico is lifting out, and 
in response, mid-level ridging is becoming re-established over 
Mexico. In addition, a significant gale-force gap wind event is 
currently ongoing to the west of Pilar in the Gulf of Tehuantepec. A 
combination of these low and mid-level steering influences is 
expected to start moving Pilar to the west and then west-southwest 
beginning tomorrow and continuing through the end of this week. The 
track guidance remains in fairly good agreement on this solution, 
though was a bit further north early on given the initial position, 
and further south towards the end of the forecast. The NHC track has 
been adjusted accordingly, and still lies in between the reliable 
TVCE and HCCA consensus aids.
 
Pilar could be near its peak intensity as it continues to battle 
moderate vertical wind shear out of the east. While this shear is 
forecast to decrease in the next 24-48 hours, this is expected to be 
offset by ocean upwelling, which is likely occurring near the slow 
moving storm currently, in addition to the strong gap-wind flow 
further west also putting a dent in the sea-surface temperatures 
along Pilar's forecast track. This effect is most accurately 
captured by the atmospheric-ocean coupled hurricane regional 
guidance, which are all notably lower than the consensus aids as 
they show Pilar traversing SSTs below 26 C over the next few days. 
The aforementioned gap winds may also import dry mid-latitude air 
near the circulation of Pilar as it begins to lose latitude. The 
most recent GFS and ECMWF runs also show a weaker system than before 
after the next 36-48 hours, so a bit more weakening is shown in the 
latest NHC forecast. This forecast splits the difference between the 
higher IVCN and HCCA consensus aids, and the lower hurricane 
regional model guidance.
 
Key Messages:
 
1. Heavy rains from Pilar will produce flash and urban flooding,
along with mudslides in areas of higher terrain of the Pacific coast
of Central America from southern El Salvador, across southern
Honduras, western Nicaragua into northern Costa Rica through
Wednesday.
 
2. Tropical storm conditions are possible along portions of the
Pacific coast of El Salvador, Honduras, and Nicaragua, where a
Tropical Storm Watch remains in effect.
 
3. Swells generated by Pilar will continue to affect the Pacific
coast of Central America during the next few days.  These swells are
likely to cause life-threatening surf and rip current conditions.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0300Z 11.9N  89.4W   50 KT  60 MPH
 12H  01/1200Z 11.9N  89.5W   50 KT  60 MPH
 24H  02/0000Z 11.7N  91.0W   50 KT  60 MPH
 36H  02/1200Z 11.3N  93.2W   45 KT  50 MPH
 48H  03/0000Z 10.6N  96.0W   40 KT  45 MPH
 60H  03/1200Z  9.8N  98.9W   40 KT  45 MPH
 72H  04/0000Z  9.4N 101.4W   40 KT  45 MPH
 96H  05/0000Z  9.0N 106.0W   40 KT  45 MPH
120H  06/0000Z 10.0N 110.0W   40 KT  45 MPH
 
$$
Forecaster Papin
 
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