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Tropical Storm Franklin Forecast Discussion Number 6
2017-08-08 04:42:07| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Mon Aug 07 2017 000 WTNT42 KNHC 080241 TCDAT2 Tropical Storm Franklin Discussion Number 6 NWS National Hurricane Center Miami FL AL072017 1000 PM CDT Mon Aug 07 2017 Satellite images and radar data from Belize show that Franklin has an expansive and nearly symmetric circulation. However, recent microwave data indicate that the cyclone does not have a well-defined inner core, which is characterized by an elliptical ring of convection that is open on the northwest side. In addition, cloud tops are not very cold near the center, and the deepest convection is located in a band well to the east of the center over the Caribbean Sea. Earlier Hurricane Hunter aircraft data indicated that maximum winds were near 50 kt, and since the satellite presentation has not improved since then, that will remain Franklin's initial intensity. Franklin appears to have turned west-northwestward and sped up just a bit with an initial motion of 300/12 kt. A mid-tropospheric ridge extending across the northern and central Gulf of Mexico should force Franklin west-northwestward and westward across the Yucatan peninsula and into the Bay of Campeche during the next day or two, which is handled well by the numerical models. After 36 hours, there is some latitudinal spread in the track guidance, likely related to how Franklin's circulation interacts with the mountainous terrain of Mexico. Since tropical cyclones in the western Bay of Campeche historically have tended to turn a little southward prior to landfall, the updated NHC track forecast is a little south of the previous forecast, leaning in the direction of the HFIP Corrected Consensus and the GFS. Given Franklin's structure and limited time before landfall, the cyclone is unlikely to strengthen before the center reaches land. Weakening is anticipated while Franklin takes about 18 hours to cross the Yucatan peninsula, but the storm should then begin to restrengthen once it reaches the warm waters of the Bay of Campeche tomorrow evening. It does appear that northerly shear may begin to increase in about 36 hours, but it does not look strong enough to prevent intensification. Continuing the pattern of following the HFIP Corrected Consensus and the ICON intensity consensus, the official forecast shows Franklin reaching hurricane intensity in about 48 hours, and then making landfall on the coast of mainland Mexico as a hurricane between 48 and 72 hours. Despite what is explicitly indicated in the forecast, Franklin's low-level center is likely to dissipate near the mountains of Mexico, with the mid-level remnants continuing westward across central Mexico. Based on the updated forecast, the government of Mexico has discontinued the Hurricane Watch for the east coast of the Yucatan peninsula but has issued a new Hurricane Watch for parts of the state of Veracruz in mainland Mexico. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 19.1N 87.3W 50 KT 60 MPH 12H 08/1200Z 19.7N 88.9W 40 KT 45 MPH...INLAND 24H 09/0000Z 20.2N 91.1W 45 KT 50 MPH...OVER WATER 36H 09/1200Z 20.5N 93.1W 55 KT 65 MPH 48H 10/0000Z 20.6N 95.2W 65 KT 75 MPH 72H 11/0000Z 20.0N 100.4W 30 KT 35 MPH...INLAND 96H 12/0000Z...DISSIPATED $$ Forecaster Berg
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