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Tropical Storm Selma Forecast Discussion Number 2
2017-10-27 16:38:55| National Hurricane Center (East Pacific)
Issued at 1000 AM CDT Fri Oct 27 2017 000 WTPZ45 KNHC 271438 TCDEP5 Tropical Storm Selma Discussion Number 2 NWS National Hurricane Center Miami FL EP202017 1000 AM CDT Fri Oct 27 2017 Selma is a sheared tropical cyclone. Early morning visible satellite images and recent microwave imagery show that the center is located near the northeastern edge of a small, but persistent cluster of deep convection. The latest subjective Dvorak intensity estimates are still below tropical storm strength, but the initial intensity remains at 35 kt, in agreement with the earlier scatterometer data. Recent satellite and microwave fixes indicate that Selma is moving northwestward at about 4 kt. A weak ridge to the north of the tropical cyclone is forecast to weaken today as a large mid-latitude trough moves into the Gulf of Mexico. This pattern should cause Selma to turn northward toward the Pacific coast of Central America tonight and early Saturday. However, there is a large spread in the guidance regarding the sharpness of the turn. The UKMET shows an immediate northward or northeastward motion and is along the right side of the guidance envelope. On the opposite side of the envelope are the GFS, HWRF, and HMON, which depict a longer north- northwestward motion and bring Selma inland near western Guatemala. The NHC forecast is closest to the ECMWF and HFIP corrected consensus models, which are a little to the right of the multi-model consensus. Given the large uncertainty in the track forecast, the government of Guatemala has issued a tropical storm watch for the entire Pacific coast of Guatemala. The shear over Selma appears to be a little stronger than initially expected, and the SHIPS guidance does not show any decrease in this shear during the next day or so. As a result, only slight strengthening is indicted before landfall, and the NHC forecast is close to the various consensus models. Since the system is small, it is expected to weaken and dissipate very quickly after it moves inland over the high terrain of Central America. It should be noted that the primary threat associated with Selma is heavy rainfall, with totals possibly as high as 10 inches over portions of El Salvador and Guatemala. This rainfall could cause life-threatening flash floods and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 11.1N 89.5W 35 KT 40 MPH 12H 28/0000Z 11.8N 89.9W 40 KT 45 MPH 24H 28/1200Z 13.0N 90.0W 40 KT 45 MPH 36H 29/0000Z 14.2N 89.8W 35 KT 40 MPH...INLAND 48H 29/1200Z...DISSIPATED $$ Forecaster Brown
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