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Tropical Depression One-E Forecast Discussion Number 1
2021-05-09 10:57:56| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Sun May 09 2021 000 WTPZ41 KNHC 090857 TCDEP1 Tropical Depression One-E Discussion Number 1 NWS National Hurricane Center Miami FL EP012021 300 AM MDT Sun May 09 2021 Satellite images and scatterometer surface wind data indicate that the low pressure area southwest of Mexico that the NHC has been monitoring for the past few days has acquired sufficient organized deep convection and has developed a well-defined inner-core wind field for the system to be designated as the first tropical depression of the 2021 Eastern North Pacific hurricane season... albeit six days early. The initial intensity of 30 kt is based on 30-kt surface winds noted in 0359 UTC and 0453 UTC ASCAT-B and ASCAT-C, respectively, scatterometer satellite data. There were some 35-kt wind vectors present east of the center, but those appeared to be rain-contaminated at that time. The 30-kt initial intensity is also supported by a 0600 UTC TAFB satellite intensity estimate of T2.0/30 kt using a curved-band feature. The initial motion estimate is 325/04 kt. For the next day or two, the tropical cyclone is forecast to move northwestward to north-northwestward around the western periphery of a weak subtropical ridge that extends westward from the southwestern Gulf of Mexico across central Mexico to just north of the system. The ridge is expected to build steadily westward over the next few days, resulting in the cyclone turning westward on Tuesday and then moving west-southwestward on Wednesday and Thursday. The HHC track forecast follows the overall trend of the consensus models TVCE and HCCA, but lies along the southern edge of the guidance envelope in anticipation of the system weakening and becoming a shallow cyclone by early Tuesday, after which it should be steered more by the low-level easterly to northeasterly trade-wind flow Recent satellite trends suggest that the depression currently is not far from tropical storm status, and SHIPS intensity data indicate that the deep-layer shear is favorable for some additional strengthening. However, shear analyses from UW-CIMSS reveal that moderate southwesterly to westerly mid-level shear is currently displacing the convection to the northeast and east of the low-level center, and this unfavorable pattern is expected to hinder overall development. As a result, the cyclone is only forecast to become a low-end tropical storm before significant deep-layer shear begins to adversely affect the system by late Monday. During the period Tuesday through Thursday, very hostile wind shear in conjunction with sea-surface temperatures cooling to near 26-deg C beneath the cyclone should result in the system degenerating into a remnant low, with dissipation expected by early Friday, if not sooner. The official intensity forecast is similar to but slightly higher than the consensus models IVCN and HCCA for the next 24 hours, and then closely follows those models thereafter. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 13.8N 107.7W 30 KT 35 MPH 12H 09/1800Z 14.5N 108.1W 35 KT 40 MPH 24H 10/0600Z 15.3N 108.6W 35 KT 40 MPH 36H 10/1800Z 15.8N 109.2W 30 KT 35 MPH 48H 11/0600Z 16.1N 110.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 11/1800Z 16.2N 110.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 12/0600Z 16.2N 112.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 13/0600Z 15.8N 115.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 14/0600Z...DISSIPATED $$ Forecaster Stewart
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