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Tropical Depression Fifteen Forecast Discussion Number 4
2019-10-15 16:33:08| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Tue Oct 15 2019 000 WTNT45 KNHC 151433 TCDAT5 Tropical Depression Fifteen Discussion Number 4 NWS National Hurricane Center Miami FL AL152019 1100 AM AST Tue Oct 15 2019 The depression doesn't looking very healthy compared to 24 hours ago when tightly curved convective bands wrapped around the center. Over the past 12 hours, the convection has devolved into an elongated north-to-south band of stratiform deep-layer cloudiness with embedded clusters of moderate to deep convection. The western semicircle of the broad circulation has degraded with at least two small low-level circulations revolving southward around the mean center. A 1045Z partial ASCAT-A pass indicated that the low-level center was located west of 21W longitude, so the initial position was adjusted farther west. Intensity estimates range from T1.5/25 kt from TAFB and the partial ASCAT pass, to 33 kt and 37 kt from UW-CIMSS ADT and SATCON, respectively. For now, the intensity will be held at 30 kt, which is an average of these estimates. The initial motion estimate remains northwestward, or 320/08 kt, but this motion is of low confidence given the broad nature of the cyclone. Surprisingly, the models remain in quite good agreement that the depression will move generally northwestward during the next couple of days and pass over or just east of the northeastern Cabo Verde Islands. A turn to the west-northwest is forecast by 72 hours and beyond due to the weak and shallow system being steered by the low-level easterly trade wind flow. The new NHC track forecast has been nudged a little to the left or west of the previous advisory track, mainly due to the more westward initial position, and lies close to the tightly packed consensus models. The environmental conditions are expected to remain somewhat conducive for slight strengthening during the next 12-18 hours. Although no longer explicitly forecast, it is still possible that the depression could briefly become a tropical storm later tonight if a burst of deep convection can develop and tighten up the inner-core wind field. By late Wednesday, however, the combination of a sharp increase in southwesterly vertical wind shear, drier mid-level air, and SSTs less than 26C should induce steady to rapid weakening, resulting in the cyclone degenerating into a remnant low by 36 hours and dissipating in 72-96 hours. Regardless of whether or not the depression becomes a tropical storm before passing near the Cabo Verde Islands, the primary threat from this system is the potential for locally heavy rainfall and flash flooding in those islands. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 15.6N 21.6W 30 KT 35 MPH 12H 16/0000Z 16.5N 22.4W 30 KT 35 MPH 24H 16/1200Z 17.7N 23.4W 30 KT 35 MPH 36H 17/0000Z 18.5N 24.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 17/1200Z 19.4N 26.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 18/1200Z 21.6N 30.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 19/1200Z...DISSIPATED $$ Forecaster Stewart
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