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Tropical Depression Four-E Forecast Discussion Number 1
2017-06-25 04:33:03| National Hurricane Center (East Pacific)
Issued at 1000 PM CDT Sat Jun 24 2017 000 WTPZ44 KNHC 250232 TCDEP4 Tropical Depression Four-E Discussion Number 1 NWS National Hurricane Center Miami FL EP042017 1000 PM CDT Sat Jun 24 2017 Satellite images indicate that the low pressure system south of Mexico has a well-defined circulation with convective banding features developing near the center. The convection appears to have enough organization to classify the system as a tropical cyclone, and the initial intensity is set at 25 kt based on Dvorak estimates of T2.0 from TAFB and T1.5 from SAB. The depression is located to the southwest of a closed mid-/ upper-level low located over the western Gulf of Mexico, and to the southeast of a large mid-tropospheric high centered over Arizona. The initial motion is west-northwestward, or 300/9 kt, and this general motion should continue for the next three days as the depression is increasingly steered by the strong high pressure to its north. Some decrease in speed is likely by days 4 and 5 once the cyclone weakens and is steered by lower-level winds. The track models are showing relatively little cross-track spread, but there are some speed differences, with the ECMWF most notably being slower than the other guidance. The NHC official track forecast is relatively close to the multi-model consensus TVCN, and there is high confidence that the cyclone will move parallel to the coast of Mexico, keeping the tropical-storm-force winds well offshore. Water vapor imagery shows the depression's outflow expanding in nearly all directions, and deep-layer shear is forecast to be very low for the entire forecast period. Therefore, strengthening is expected for the next 48 hours before the cyclone reaches colder water. The NHC intensity forecast closely follows HCCA during the first 36 hours but then diverges from HCCA and indicates a peak intensity occurring at 48 hours, which is closer in timing to the peak intensities shown by SHIPS, the GFS, and the ECMWF models. Cold water should cause the cyclone to degenerate to a remnant low by day 4 or 5. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 14.3N 100.0W 25 KT 30 MPH 12H 25/1200Z 15.1N 101.6W 35 KT 40 MPH 24H 26/0000Z 15.9N 103.4W 45 KT 50 MPH 36H 26/1200Z 16.8N 105.2W 55 KT 65 MPH 48H 27/0000Z 17.9N 106.9W 60 KT 70 MPH 72H 28/0000Z 19.5N 110.5W 45 KT 50 MPH 96H 29/0000Z 20.5N 113.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 30/0000Z 21.0N 116.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg
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