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Tropical Depression Twenty-E Forecast Discussion Number 1
2018-09-25 10:43:46| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Tue Sep 25 2018 831 WTPZ45 KNHC 250843 TCDEP5 Tropical Depression Twenty-E Discussion Number 1 NWS National Hurricane Center Miami FL EP202018 300 AM MDT Tue Sep 25 2018 The low pressure system that NHC has been monitoring off the coast of southwestern Mexico has now become a tropical depression, the twentieth of the eastern North Pacific 2018 season. ASCAT data from around 0400 UTC indicated that the system had a well-defined center and maximum winds in the 25-30 kt range. In addition, satellite images show deep convection increasing in coverage and intensity near the center. The initial wind speed is set at 30 kt, based on the ASCAT data, but this is a little below the latest Dvorak estimate from TAFB. Since the depression has only recently formed, the initial motion is an uncertain 280/7 kt. Mid-level ridging to the north of the system should keep the depression on a westward to west- northwestward path at about the same forward speed for the next few days. Thereafter, the models show the ridge breaking down due to a large cut off deep-layer low moving toward the west coast of the United States. In response, the cyclone is expected to turn to the northwest this weekend. The models agree on this overall scenario, but there is a fair amount of spread by the end of the forecast period. The NHC track forecast lies near the middle of the guidance envelope and close to the best performing models, the consensus aids. The environmental conditions appear favorable for the depression to strengthen. SSTs are expected to remain quite warm beneath the cyclone for the next several days while vertical wind shear values are around 10 kt or less. These conditions combined with a moist airmass should allow for at least steady strengthening during the next 3 to 4 days. Some weakening is possible by the end of the forecast period due to slightly cooler SSTs and an increase in shear. The NHC intensity forecast shows a slower rate of strengthening than the guidance, since the system is still in the developing stage, but predicts peak winds near the IVCN consensus model. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 14.5N 107.2W 30 KT 35 MPH 12H 25/1800Z 14.9N 108.2W 35 KT 40 MPH 24H 26/0600Z 15.5N 109.8W 40 KT 45 MPH 36H 26/1800Z 15.8N 111.2W 55 KT 65 MPH 48H 27/0600Z 16.1N 112.6W 70 KT 80 MPH 72H 28/0600Z 16.9N 115.6W 90 KT 105 MPH 96H 29/0600Z 18.3N 118.1W 90 KT 105 MPH 120H 30/0600Z 20.7N 119.5W 85 KT 100 MPH $$ Forecaster Cangialosi
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