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| #982856 (Received by flhurricane at: 4:54 PM 18.Sep.2019) TCDAT5 Tropical Storm Jerry Discussion Number 6 NWS National Hurricane Center Miami FL AL102019 500 PM AST Wed Sep 18 2019 Jerry continues to strengthen this afternoon, as indicated by 1-min GOES-16 satellite imagery, with a large burst of convection close to the center. In addition, microwave data show that the central structure has improved, displaying a tightly wrapped band near the center. The initial wind speed is set to 50 kt, on the conservative side of the intensity estimates. The storm should become a hurricane on Thursday while it is moving over very warm waters with light shear. Dropsondes from the NOAA G-IV aircraft this afternoon show that Jerry is surrounded by some very dry air in the lower to mid-levels, and this is likely the main limiting factor on the cyclone`s strengthening rate in the near term. By 48 hours, almost all of the models show an increase in northwesterly shear due to flow from an upper-level ridge, which seems likely to cause some weakening. At long range, Jerry is likely to interact with a mid-latitude trough, which is notoriously difficult to forecast. Only small changes were made to the previous wind speed prediction, and this advisory is close to a blend of the various consensus aids. The initial motion continues to be west-northwestward, or 290/13 kt. There`s no substantial change to the track forecast on this package, with a subtropical ridge providing a well-defined steering current. This ridge should move Jerry along at a faster forward speed in about the same direction for the next couple of days, taking the center close to but north of the northern Leeward Islands. Afterward, a northwest to northward turn, influenced by a weakness in the aforementioned ridge left behind by Humberto and a new mid-latitude shortwave, is anticipated. The new forecast is very close to the previous one and a blend of the latest ECMWF ensemble mean and the corrected-consensus HCCA. Key Messages: 1. Jerry is expected to become a hurricane before it moves close to the northern Leeward Islands Friday. Although the core of Jerry is currently expected to pass north of the islands, tropical-storm- force winds and locally heavy rainfall are possible, and tropical storm watches have been issued for a portion of this area. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 15.0N 50.5W 50 KT 60 MPH 12H 19/0600Z 15.7N 52.5W 60 KT 70 MPH 24H 19/1800Z 16.7N 55.3W 70 KT 80 MPH 36H 20/0600Z 17.8N 58.3W 70 KT 80 MPH 48H 20/1800Z 19.1N 61.4W 65 KT 75 MPH 72H 21/1800Z 21.5N 66.5W 60 KT 70 MPH 96H 22/1800Z 25.2N 70.0W 60 KT 70 MPH 120H 23/1800Z 28.5N 69.5W 60 KT 70 MPH $$ Forecaster Blake |
