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Tropical Storm Nana Forecast Discussion Number 2
2020-09-01 18:56:37| National Hurricane Center (Atlantic)
Issued at 100 PM EDT Tue Sep 01 2020 000 WTNT41 KNHC 011656 TCDAT1 Tropical Storm Nana Special Discussion Number 2 NWS National Hurricane Center Miami FL AL162020 100 PM EDT Tue Sep 01 2020 An Air Force Reserve reconnaissance aircraft investigating the vigorous disturbance south of Jamaica this morning has found that the system has a well-defined, closed circulation center. The aircraft also measured 60 kt at 925 mb in the northeastern quadrant and reliable SFMR surface winds of 45 kt. Based on these data, the system has been upgraded to Tropical Storm Nana, the 14th named tropical storm of the 2020 Atlantic hurricane season. The initial motion estimate is an uncertain 280/14 kt, No significant changes were made to the previous track forecast. A strong deep-layer to the north of the system is expected to build slowly westward over the next few days, keeping the disturbance moving in a general west-northwestward to westward direction through 48 hours, followed by a turn toward the west-southwest shortly thereafter when the system will be inland over Central America. The NHC official forecast track lies close to a blend of the simple consensus models TVCN and GFEX, and the corrected-consensus model HCCA. Nana has developed a well-defined upper-level anticyclone, with outflow gradually improving in all quadrants. Modest northeasterly to easterly vertical wind shear is expected to gradually subside to less than 10 kt by 48 hours, which should allow for at least some slow but steady strengthening, given that sea-surface temperatures (SST) will be 29.5-30.5 deg C along the track. Some dry air intrusions might hinder development for the next 24 hours or so, but the global and regional models still indicate that the atmosphere will moisten thereafter, and continue to moisten right up until landfall. Based on the higher initial intensity and the mostly favorable environmental conditions expected after 24 hours, the peak forecast intensity has been increased to 65 kt at 48 hours, just prior to landfall. Due to the Nana's expected proximity to Belize in 48 hours, a Tropical Storm Watch has been issued for that country. Additional watches and possible warnings will likely be required later today for Guatemala and the southern portion of the Yucatan Peninsula. KEY MESSAGES: 1. Tropical Storm Nana is now forecast to be a hurricane as it approaches the coast, and interests in Honduras, Guatemala, Belize and Yucatan should closely monitor the progress of this storm. Strong winds, dangerous storm surge and very heavy rainfall causing flash flooding are becoming more likely from Nana. FORECAST POSITIONS AND MAX WINDS INIT 01/1700Z 16.6N 77.9W 45 KT 50 MPH 12H 02/0000Z 16.6N 79.5W 50 KT 60 MPH 24H 02/1200Z 16.7N 82.3W 55 KT 65 MPH 36H 03/0000Z 16.8N 85.1W 60 KT 70 MPH 48H 03/1200Z 16.8N 87.4W 65 KT 75 MPH 60H 04/0000Z 16.5N 89.6W 30 KT 35 MPH...INLAND 72H 04/1200Z 15.7N 91.7W 15 KT 15 MPH...POST-TROP/REMNT LOW 96H 05/1200Z...DISSIPATED $$ Forecaster Stewart
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