####018004212#### WTPZ44 KNHC 010239 TCDEP4 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