ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM MARTY DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP172015 1000 PM CDT SAT SEP 26 2015 The cyclone has become better organized during the past several hours with a large burst of convection recently trying to form a central dense overcast. In addition, the latest microwave images show some structure to the inner core, along with more pronounced banding features south of the center. On the basis of the increased organization and the latest Dvorak estimate from TAFB, the initial wind speed is set to 35 kt. Marty is now moving northward at about 4 kt. A turn to the north-northeast is forecast on Sunday due to the storm moving around the western side of a weak mid-level ridge over the far eastern Pacific west of Central America. While Marty will get close to being caught by a trough over Mexico, most of the guidance suggest that the cyclone will be left behind in a couple of days southwest of the coast of Mexico due to the trough moving away. Marty would then drift west-northwestward in the low-level flow as a weaker cyclone. The NHC forecast has shifted eastward in the first couple of days, then westward at longer range with more model guidance showing the solution where the cyclone is left behind. This is an uncertain forecast, however, and it wouldn't take much of a deviation for stronger winds to approach the coast. A tropical storm watch could be issued for a portion of the coast of Mexico on Sunday morning. Marty is currently in an environment of light wind shear, high mid- level moisture and very warm waters. These favorable conditions should last for the next 24-36 hours and promote intensification during that time. While none of the deterministic guidance shows rapid intensification, the SHIPS-RI index shows about a 70 percent chance of a 25-kt increase in the first 24 hours. The intensity forecast is set at the upper end of the guidance, about 5 kt above the previous prediction through 36 hours. After that time, almost all of the global models show a significant increase in southwesterly shear, which should cause Marty to weaken and probably dissipate by day 5. The official forecast is very close to the previous one and the intensity consensus after 72 hours. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 13.6N 103.0W 35 KT 40 MPH 12H 27/1200Z 14.2N 102.8W 45 KT 50 MPH 24H 28/0000Z 14.9N 102.6W 55 KT 65 MPH 36H 28/1200Z 15.4N 102.3W 60 KT 70 MPH 48H 29/0000Z 15.8N 102.0W 55 KT 65 MPH 72H 30/0000Z 16.0N 102.0W 45 KT 50 MPH 96H 01/0000Z 16.2N 102.3W 30 KT 35 MPH 120H 02/0000Z 16.5N 103.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Blake NNNN
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Page last modified: Thursday, 31-Dec-2015 12:09:52 UTC