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Tropical Depression Nine-E Forecast Discussion Number 1
2019-08-12 04:51:54| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Sun Aug 11 2019 000 WTPZ44 KNHC 120251 TCDEP4 Tropical Depression Nine-E Discussion Number 1 NWS National Hurricane Center Miami FL EP092019 900 PM MDT Sun Aug 11 2019 The broad low pressure system that the NHC has been tracking the past several days has finally developed a well-defined surface circulation and enough organized deep convection to be classified as a tropical depression. A late-arriving 1716Z ASCAT-C scatterometer pass indicated the surface wind field was possibly closed at that time, but since then deep convection with tops of -75C to -80C have persisted near and to the west of the mid-level circulation center, suggesting that a low-level center has likely closed off now. Dvorak satellite intensity estimates are T1.5/25 kt from both TAFB and SAB, but the initial intensity is set at 30 kt based on 30-31 kt winds indicated in the aforementioned scatterometer data. The initial motion is estimated to be west-northwestward or 295/12 kt, based primarily on scatterometer and passive microwave fixes. The small cyclone is expected to move west-northwestward around the southern periphery of a deep-layer ridge for the next 3 days until dissipation occurs. The NHC track forecast lies near the southern portion of the guidance envelope, between the TVCE consensus model and the ECMWF-ensemble mean model. The small cyclone only has about 36 hours to strengthen before the system moves over sub-26 deg C SSTs. The shear is forecast to be low at less than 10 kt for the next 72 hours or so, even decreasing to near 5 kt in 24-36 h, which would normally result in significant development. However, intermittent intrusions of dry mid-level air are expected to disrupt the typical intensification process, thus only modest strengthening is forecast through 36 h, after which much cooler waters will induce a weakening trend. The official intensity forecast closely follows a blend of the HCCA and IVCN intensity consensus models. FORECAST POSITIONS AND MAX WINDS INIT 12/0300Z 18.9N 109.8W 30 KT 35 MPH 12H 12/1200Z 19.4N 111.2W 35 KT 40 MPH 24H 13/0000Z 20.3N 113.1W 35 KT 40 MPH 36H 13/1200Z 21.3N 115.3W 35 KT 40 MPH 48H 14/0000Z 22.1N 117.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 15/0000Z 23.7N 123.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/0000Z...DISSIPATED $$ Forecaster Stewart
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