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Tropical Depression Nine-E Forecast Discussion Number 2
2021-07-31 04:36:33| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Fri Jul 30 2021 000 WTPZ44 KNHC 310236 TCDEP4 Tropical Depression Nine-E Discussion Number 2 NWS National Hurricane Center Miami FL EP092021 800 PM PDT Fri Jul 30 2021 The depression is struggling. Aside from a stray cell or two, the cyclone has been nearly devoid of deep convection since the diurnal convective minimum earlier this evening. AMSR data near 22Z indicated that multiple weak swirls may be embedded within the broader circulation sampled earlier today by ASCAT. The initial intensity remains 25 kt for this advisory. Confidence in the track forecast is unusually low. The initial position, and therefore also the motion estimate, is highly uncertain due to the disorganized nature of the depression. On top of that, the track guidance is in extremely poor agreement regarding even the basics of the future track of the cyclone. Hilda, located relatively close to the east (about 10 degrees) may have some impact on the depression's track during the next 5 days. In fact, the GFS explicitly forecasts that a binary interaction will occur between the two tropical cyclones. Other models like the ECMWF move both systems steadily, and mostly independently, westward. As a course of least regret, the NHC track forecast is close to the previous advisory and multi-model consensus, between those two scenarios. Large changes to the track forecast may be necessary on Saturday if the track guidance begins to converge on a single solution. Warm water and moderate shear could allow for some strengthening during the next few days, if the depression can redevelop and sustain organized convection. The NHC intensity forecast assumes that will happen to some degree and has not been substantially changed. It is also possible that dry air in the environment could continue to inhibit convection as the depression moves westward. In that case, the official intensity forecast could wind up being a little too high. The NHC intensity forecast is well within the guidance envelope, but is a touch above the latest consensus. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 12.5N 126.2W 25 KT 30 MPH 12H 31/1200Z 12.4N 126.6W 30 KT 35 MPH 24H 01/0000Z 12.3N 127.3W 30 KT 35 MPH 36H 01/1200Z 12.4N 128.4W 35 KT 40 MPH 48H 02/0000Z 12.7N 130.0W 35 KT 40 MPH 60H 02/1200Z 13.1N 131.6W 35 KT 40 MPH 72H 03/0000Z 13.4N 133.0W 40 KT 45 MPH 96H 04/0000Z 13.8N 135.9W 45 KT 50 MPH 120H 05/0000Z 14.5N 138.9W 50 KT 60 MPH $$ Forecaster Zelinsky
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