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Tropical Storm Pilar Forecast Discussion Number 3
2017-09-24 10:56:22| National Hurricane Center (East Pacific)
Issued at 400 AM CDT Sun Sep 24 2017 000 WTPZ43 KNHC 240856 TCDEP3 Tropical Storm Pilar Discussion Number 3 NWS National Hurricane Center Miami FL EP182017 400 AM CDT Sun Sep 24 2017 Recent microwave imagery from an AMSU overpass indicate that the low-level structure of Pilar is rather messy. It is possible that the low-level center may be reforming under the convection to the west, but there have been no recent higher resolution microwave or ASCAT overpasses to confirm this. Despite this, a blend of Dvorak estimates from TAFB and SAB now supports an initial intensity of 40 kt. Given a lack of any other data to go off of, that has been used as the basis for the initial intensity. The initial motion estimate is a highly uncertain 335/4 kt, based in part on extrapolation from the previous motion. There is still a high spread among the models in the first 24 h of the forecast. Several models, including the GFS, forecast that Pilar will move quickly inland and dissipate. A few others, like the HWRF, keep the center of Pilar just far enough offshore to maintain a coherent vortex for about 72 hours. Finally, the ECMWF is an outlier in showing Pilar reforming to the west and stalling off the west coast of Jalisco for 24 h before moving inland and dissipating. In the interest of continuity, the NHC forecast for this advisory does not account for any reformation of the center, and shows Pilar moving steadily northward to north-northwestward until dissipation, like the HWRF. The NHC forecast is close to the multi-model consensus, though in this case so many members quickly show dissipation, that relatively few members are averaged together. The intensity forecast is also complicated by land interaction. SSTs near the southwest coast of Mexico are very warm, and the shear is forecast to remain low for about 36 h. The NHC intensity forecast only shows slight intensification since significant land interaction is still expected. In the event that Pilar stays farther offshore, it could become stronger than currently forecast. Regardless of how much Pilar intensifies, a sharp increase in shear around 48 h should quickly cause the cyclone to weaken to a remnant low and eventually dissipate. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 19.1N 105.6W 40 KT 45 MPH 12H 24/1800Z 19.5N 105.8W 45 KT 50 MPH 24H 25/0600Z 20.2N 105.9W 45 KT 50 MPH 36H 25/1800Z 21.0N 105.8W 40 KT 45 MPH 48H 26/0600Z 22.0N 106.0W 30 KT 35 MPH 72H 27/0600Z 24.0N 107.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 28/0600Z...DISSIPATED $$ Forecaster Zelinsky
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