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#1014929 (Received by flhurricane at: 4:57 AM 02.Sep.2020) TCDAT1 Tropical Storm Nana Discussion Number 5 NWS National Hurricane Center Miami FL AL162020 500 AM EDT Wed Sep 02 2020 Nana`s Central Dense Overcast has become a little better defined, with cloud tops to -80 deg C or colder. Upper-level outflow continues to be somewhat inhibited over the northern portion of the circulation. SFMR-observed surface winds and adjusted flight-level winds from an Air Force Hurricane Hunter aircraft indicated an intensity of 50 kt. Although northerly shear is likely to limit intensification, the environment is conducive enough for Nana to strengthen into a hurricane later today. The official intensity forecast is close to the Decay-SHIPS prediction based on the ECMWF global model forecast fields. Center fixes from the aircraft indicate that the motion continues to be generally westward, or 270/16 kt, to the south of a strong mid-level high pressure area. Over the next couple of days, the ridge is expected to be maintained or to build a little more to the west. This should keep Nana on a westward or slightly south-of-west track until it moves into Central America. The official track forecast is close to the previous one and also very close to the latest Florida State University Superensemble prediction. Observations from the aircraft and NOAA data buoy 42057 indicate that Nana is a rather small tropical cyclone, with tropical-storm-force winds extending 60 n mi or less from the center. KEY MESSAGES: 1. Tropical Storm Nana is forecast to be a hurricane as it approaches the coast, and interests in Honduras, Guatemala, Belize, and the Yucatan Peninsula 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 02/0900Z 17.0N 82.7W 50 KT 60 MPH 12H 02/1800Z 16.9N 85.0W 60 KT 70 MPH 24H 03/0600Z 16.8N 87.6W 65 KT 75 MPH 36H 03/1800Z 16.5N 89.8W 50 KT 60 MPH...INLAND 48H 04/0600Z 16.4N 92.1W 30 KT 35 MPH...INLAND 60H 04/1800Z 16.1N 93.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 05/0600Z...DISSIPATED $$ Forecaster Pasch |