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Tropical Depression Nine-E Forecast Discussion Number 6
2021-08-01 04:41:26| National Hurricane Center (East Pacific)
Issued at 500 PM HST Sat Jul 31 2021 000 WTPZ44 KNHC 010241 TCDEP4 Tropical Depression Nine-E Discussion Number 6 NWS National Hurricane Center Miami FL EP092021 500 PM HST Sat Jul 31 2021 The tropical depression's classification as a tropical cyclone is in doubt. It has not produced sustained organized deep convection for over a day and is nearly devoid of even moderate convection at this time. In addition, the surface wind field is poorly defined. A prominent swirl noted in the previous forecast package moved quickly southeastward and dissipated, leaving only a broad, elongated low centered east of previous estimates. The most recent TAFB Dvorak fix still supports an intensity of 25 kt. If organized deep convection does not redevelop soon, the system could become a remnant low or open into a trough at any time. Even if the depression is able to maintain its status as a tropical cyclone, the close proximity of rapidly intensifying Hilda to the east will likely prevent it from strengthening during the next 72 h, and this is reflected in the new NHC intensity forecast. After that time, Hilda is forecast to weaken, which could open a window for intensification (or re-formation) late in the forecast period. The official intensity forecast is now below the intensity consensus at most forecast hours. It is worth noting that the operational regional hurricane models do not capture storm-to-storm interactions very well, and this is likely influencing the relatively high intensity forecast produced by the HWRF. The eastward adjustment of the initial position has necessitated a large eastward shift in the forecast track based on the new center position. Otherwise, the general reasoning behind the NHC track forecast is similar to the previous advisory. A slow, westward to west-northwestward motion is expected for the next few days. Beyond that time, differences regarding the specifics of any direct interaction with Hilda is the primary source of uncertainty in the track forecast. Confidence in the forecast, especially at that long range, remains low. The NHC forecast is based primarily on a consensus of the GFS and ECMWF global models. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 11.5N 127.5W 25 KT 30 MPH 12H 01/1200Z 11.8N 128.4W 25 KT 30 MPH 24H 02/0000Z 12.0N 130.0W 30 KT 35 MPH 36H 02/1200Z 12.2N 131.5W 30 KT 35 MPH 48H 03/0000Z 12.5N 133.0W 30 KT 35 MPH 60H 03/1200Z 12.9N 134.2W 30 KT 35 MPH 72H 04/0000Z 13.5N 135.6W 30 KT 35 MPH 96H 05/0000Z 14.5N 138.0W 35 KT 40 MPH 120H 06/0000Z 15.5N 141.0W 40 KT 45 MPH $$ Forecaster Zelinsky
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