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Tropical Storm Nana Forecast Discussion Number 7
2020-09-02 22:36:29| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Wed Sep 02 2020 000 WTNT41 KNHC 022036 TCDAT1 Tropical Storm Nana Discussion Number 7 NWS National Hurricane Center Miami FL AL162020 400 PM CDT Wed Sep 02 2020 Nana continues to feel the effects of about 15 kt of northerly vertical shear, as the low-level center is located near the northern edge of the main convective mass. Data from the last Air Force Reserve Hurricane Hunter Mission showed that the flight-level winds at 850 mb were a little lower than earlier. However, incomplete SFMR data suggested surface winds near 50 kt, and the aircraft reported that the central pressure is near 999 mb. The initial intensity is held at 50 kt, although this could be a little generous. The initial motion is westward or 270/13 kt. A low- to mid-level ridge to the north of the cyclone is forecast to keep steering Nana toward the west, or maybe just south of west, for the remainder of the cyclone's life. The new forecast track, which again is changed only slightly from the previous forecast, calls for the cyclone to pass north of the Bay Islands this evening, then make landfall over central or southern Belize in about 12-18 h. Nana is running out of time to strengthen before landfall, and between that and the ongoing shear none of the intensity guidance forecasts it to become a hurricane before landfall. However, any strong convective burst could spin up the cyclone, and since the bursts have been frequent today the intensity forecast calls for Nana to strengthen to near hurricane strength at landfall. After landfall, steady weakening is expected. Several of the global models now show the remnants of Nana emerging over the Gulf of Tehuantepec in 48-60 h. However, these models continue to forecast dissipation even over water, so the forecast dissipation time is unchanged since the previous advisory. KEY MESSAGES: 1. Nana could bring hurricane conditions and dangerous storm surge tonight to portions of the coast of Belize, and a hurricane warning is in effect. Preparations to protect life and property should be rushed to completion. 2. Tropical storm conditions are expected in the tropical storm warning areas in Belize, the Bay Islands, Guatemala, and the Yucatan Peninsula of Mexico by tonight. 3. Heavy rainfall with isolated maximum amounts as high as 8 to 12 inches could result in flash flooding in Belize, Guatemala, and portions of southeastern Mexico and the Yucatan Peninsula. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 17.0N 85.9W 50 KT 60 MPH 12H 03/0600Z 16.8N 87.8W 60 KT 70 MPH 24H 03/1800Z 16.6N 90.1W 45 KT 50 MPH...INLAND 36H 04/0600Z 16.4N 92.4W 30 KT 35 MPH...INLAND 48H 04/1800Z 16.2N 94.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 05/0600Z...DISSIPATED $$ Forecaster Beven
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