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Tropical Depression Six Forecast Discussion Number 3
2019-08-27 10:43:46| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Tue Aug 27 2019 000 WTNT41 KNHC 270843 TCDAT1 Tropical Depression Six Discussion Number 3 NWS National Hurricane Center Miami FL AL062019 500 AM EDT Tue Aug 27 2019 The satellite presentation during the past several hours shows some curved banding improvement associated with the cyclone, particularly in the southeast quadrant, however, the circulation is still poorly defined. In fact, imagery reveals multiple swirls rotating about a large circulation. No changes to the subjective satellite intensity estimates, from both TAFB and SAB, and the initial intensity is held at 30 kt for this advisory. The 25-30 kt of westerly shear, indicated by the UW-CIMSS shear product, is forecast to decrease somewhat around mid-period while the system remains over warm oceanic sea surface temperatures. This, along with some baroclinic forcing in response to an approaching mid-latitude trough from the northeast United States, should allow for the cyclone to modestly strengthening. The Florida State Cyclone Phase Evolution forecast, and the global models, including the ECMWF simulated infrared imagery, now indicate the cyclone completing an extratropical transition in 3 days, and the official forecast is adjusted accordingly. Afterward, as extratropical low quickly approaches eastern Canada, the large-scale models show the cyclone becoming absorbed by a larger baroclinic system embedded in the westerlies, and this is also indicated in the official forecast. The initial motion is estimated to be a generally southward drift, or 125/2 kt, within weak low to mid-level steering flow residing between the Bermuda high to the east and a mid-level ridge over the mid-Atlantic states. The depression is forecast to move little through today as it remains in the aforementioned weak steering current. Afterward, a mid-latitude shortwave trough is forecast to move toward the northeastern United States on Wednesday, and should induce a northeastward motion with an increase in forward speed, away from the eastern seaboard. Only a slight adjustment to the left of the previous forecast was made to align more with the reliable NOAA HCCA and TVCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 31.0N 71.6W 30 KT 35 MPH 12H 27/1800Z 31.4N 71.6W 30 KT 35 MPH 24H 28/0600Z 32.5N 71.7W 35 KT 40 MPH 36H 28/1800Z 34.1N 71.4W 35 KT 40 MPH 48H 29/0600Z 36.7N 69.9W 40 KT 45 MPH 72H 30/0600Z 42.9N 63.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 31/0600Z 49.8N 55.6W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 01/0600Z...DISSIPATED $$ Forecaster Roberts
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