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Tropical Depression Nine-E Forecast Discussion Number 3
2021-07-31 10:36:10| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Sat Jul 31 2021 000 WTPZ44 KNHC 310836 TCDEP4 Tropical Depression Nine-E Discussion Number 3 NWS National Hurricane Center Miami FL EP092021 200 AM PDT Sat Jul 31 2021 The depression remains poorly organized this morning. Deep convection remains limited, and recent scatterometer data show that the circulation is elongated from east to west. The initial intensity is maintained at 25 kt, which could be generous based on the latest ASCAT data. As mentioned in the previous advisory, the confidence in the track and intensity forecast for the depression is quite low due to the current lack of organization of the system, and the potential for some interaction with Tropical Storm Hilda located to its northeast. The ASCAT data was helpful in pinpointing the center location overnight, and the latest fixes indicate that the cyclone is moving just south of due west or 265/5 kt. The track guidance generally agrees on a slow west or west-southwest heading over the next 12-24 hours followed by a west or west-northwest motion through 48-60 hours. After that time, the track guidance begins to diverge with the GFS showing a binary interaction of the depression and Hilda by days 4 and 5. Most of the remainder of the guidance keeps enough separation between the systems that the depression continues generally moving westward or west-northwestward through the end of the forecast period. The NHC track forecast is once again close to the various multi-model consensus aids, and is slightly slower than the previous official forecast. Although the depression is located over warm water, moderate easterly shear and dry air entrainment have prevented strengthening since genesis occurred. Given the current poor organization of the system and the marginal environment, only slow strengthening is indicated over the next few days. Another plausible scenario is that the system fails to produce organization deep convection within the next 12 to 24 hours, and it degenerates into a broad low pressure area along the ITCZ. Given this uncertainty, the NHC intensity forecast has been lowered slightly and is in best agreement with the IVCN intensity aid. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 12.3N 127.0W 25 KT 30 MPH 12H 31/1800Z 12.2N 127.5W 25 KT 30 MPH 24H 01/0600Z 12.1N 128.3W 30 KT 35 MPH 36H 01/1800Z 12.2N 129.6W 30 KT 35 MPH 48H 02/0600Z 12.5N 131.3W 35 KT 40 MPH 60H 02/1800Z 12.8N 132.8W 35 KT 40 MPH 72H 03/0600Z 13.1N 134.2W 40 KT 45 MPH 96H 04/0600Z 13.7N 136.5W 45 KT 50 MPH 120H 05/0600Z 14.5N 138.5W 45 KT 50 MPH $$ Forecaster Brown
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