ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM Tropical Storm John Discussion Number 14 NWS National Hurricane Center Miami FL EP102024 300 AM CST Thu Sep 26 2024 Recent TROPICS/TMS and SSMIS microwave passes indicated an improved inner core with a 70 percent closed small eye feature. The UW-CIMSS objective intensity guidance ranges from 56 to 65 kt, and the latest SATCON analysis indicated an intensity of 61 kt. The subjective satellite estimates from TAFB and SAB are 65 and 55 kt, respectively. The initial intensity is set at 60 kt using a blend of these data. The ocean sea surface temperatures are very warm, and the shear is low, and there is ample moisture in the low to mid-portions of the atmosphere for John to quickly strengthen before the cyclone moves over the coast on Friday. The UW-CIMSS AI RI index and the SHIPS statistical-dynamical RI model both continue to show increasing chances of John quickly strengthening during the next 24 hrs and the NHC intensity forecast follows suit and shows a peak of 85 kt before landfall. The initial motion is estimated to be west-northwestward, or 285/3 kt and is being steered by a mid-tropospheric ridge centered over Northern Mexico. John should continue in this general motion through today, followed by a gradual turn to the northwest by this evening. On the forecast track, the center of John is forecast to approach and move along the coast of southwestern Mexico or just inland on Friday. The official track forecast is adjusted a little to the left of the previous one and follows a compromise of the skilled HCCA consensus model and the ECMWF global model, which has been performing the best with this system. The wind radii have been adjusted for this advisory, and was based on a 0426 UTC METOP-C scatterometer overpass. It cannot be emphasized enough that catastrophic life-threatening flash flooding and mudslides are expected to continue through the end of the week for portions of the Mexican States of Guerrero, Oaxaca and Michoacan. KEY MESSAGES: 1. Tropical Storm John will bring additional very heavy rainfall to coastal portions of southwest Mexico through Friday. The additional rainfall totals will be falling across areas that have received very heavy rainfall amounts over the past few days. This heavy rainfall will likely cause significant and catastrophic life-threatening flash flooding and mudslides to the Mexican States of Guerrero, Oaxaca and Michoacan. 2. John is forecast to strengthen to a hurricane before landfall, and a Hurricane Warning is in effect along the coastline of southwestern Mexico, where tropical storm conditions could begin during the next few hours. Tropical Storm Warnings are also in effect for portions of the area and has been extended westward to Manzanillo. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 17.1N 102.5W 60 KT 70 MPH 12H 26/1800Z 17.2N 102.6W 75 KT 85 MPH 24H 27/0600Z 17.8N 103.0W 85 KT 100 MPH 36H 27/1800Z 18.8N 103.6W 45 KT 50 MPH 48H 28/0600Z 19.7N 104.7W 30 KT 35 MPH 60H 28/1800Z 20.2N 106.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 29/0600Z...DISSIPATED $$ Forecaster Roberts NNNN
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Page last modified: Tuesday, 31-Dec-2024 12:10:17 UTC