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Tropical Storm Narda Forecast Discussion Number 4
2019-09-29 10:32:28| National Hurricane Center (East Pacific)
Issued at 400 AM CDT Sun Sep 29 2019 000 WTPZ41 KNHC 290832 TCDEP1 Tropical Storm Narda Discussion Number 4 NWS National Hurricane Center Miami FL EP162019 400 AM CDT Sun Sep 29 2019 Satellite images and Acapulco radar data show that the storm has become a little better organized with some evidence of banding features. Upper-level outflow is fairly well defined over the southern semicircle of the circulation while the cyclone continues to experience some northeasterly shear. Based on data from a scatterometer overpass, the current intensity is set at 40 kt which is also the mean of Dvorak estimates from TAFB and SAB. The intensity forecast for Narda is problematic and uncertain, since the future strength of the cyclone depends on how much the cyclone will interact with the mountainous land mass of southwestern Mexico during the next few days. Some of the models, such as the ECMWF and GFS, take the cyclone inland within the next 24 hours and do not show the system recovering from its land interaction in 24-48 hours. A little more strengthening should occur today, assuming the center remains offshore. The official intensity forecast assumes that the center will move along the coast within the next day or so, and this would cause some weakening and disruption of the circulation. The NHC intensity forecast is in fairly close agreement with the LGEM guidance. The center is not easy to locate, but my best estimate of initial motion is northwestward or 315/7 kt. Over the next couple of days, the tropical cyclone is likely to move generally northwestward along the southwestern periphery of a large high pressure area. Later in the period, a trough approaching the northern Baja California peninsula should cause the system to turn toward the north-northwest. The official forecast is similar to the previous one, and close to the corrected dynamical model consensus guidance. The primary threat from Narda is very heavy rainfall, which should result in life-threatening flash flooding and mudslides over portions of the southern coast of Mexico. Rainfall totals of up to 15 inches are possible. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 16.0N 101.0W 40 KT 45 MPH 12H 29/1800Z 17.4N 102.4W 45 KT 50 MPH 24H 30/0600Z 19.3N 104.6W 35 KT 40 MPH...INLAND 36H 30/1800Z 21.3N 106.4W 30 KT 35 MPH 48H 01/0600Z 22.8N 107.9W 35 KT 40 MPH 72H 02/0600Z 25.0N 109.5W 35 KT 40 MPH 96H 03/0600Z 26.5N 110.0W 25 KT 30 MPH 120H 04/0600Z 27.5N 110.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Pasch
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