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Tropical Depression EIGHT Forecast Discussion Number 1
2016-08-28 16:52:00| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT SUN AUG 28 2016 000 WTNT43 KNHC 281451 TCDAT3 TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082016 1100 AM EDT SUN AUG 28 2016 The area of low pressure located west of Bermuda has been producing intermittent organized deep convection for the last 24 hours or so, and the convection has increased markedly since 06Z. Given this, and the well-defined center shown by an overnight ASCAT pass, advisories are now being initiated on this system as a tropical cyclone. The initial intensity is estimated to be 30 kt based on the latest Dvorak estimates of T2.0/30 kt from TAFB and SAB. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the depression this afternoon. The environment is only expected to be marginally conducive for intensification, with moderate southeasterly to easterly shear expected to become southwesterly and increase further in 36 to 48 hours. As a result, only modest strengthening is shown in the official forecast, with the depression expected to become a tropical storm in the next day or two. After that time, the global models show the cyclone opening up along a frontal zone well offshore of the northeastern United States. However, there is some disagreement in when this will occur, with the GFS showing the cyclone dissipating in about 3 days, and the ECMWF hanging onto it until around day 5. As a compromise, the NHC forecast shows dissipation after day 4, but this timing is quite uncertain. The depression is currently situated south of a mid-level ridge that extends from the Mid-Atlantic states into the western Atlantic, and the initial motion estimate is 280/08. The ridge is forecast to break down and shift eastward during the next 2-3 days, which should result in the cyclone gradually turning poleward and then recurving during the next 72 hours. The NHC track forecast is close to a blend of the GFS and ECMWF models through dissipation. This forecast keeps the center of the cyclone east of the Outer Banks of North Carolina, but a tropical storm watch may be needed for that area later today. Based on an evaluation of satellite imagery and data during the past few days, it appears that the remnants of Tropical Storm Fiona are not directly responsible for the genesis of this depression. The Fiona remnants were absorbed into a separate area of pre-existing vorticity, with the current depression developing out of the combined system. As a result, this is considered to be a new tropical cyclone, not a regeneration of a previous tropical cyclone. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 31.5N 70.0W 30 KT 35 MPH 12H 29/0000Z 32.1N 71.6W 30 KT 35 MPH 24H 29/1200Z 32.9N 73.3W 30 KT 35 MPH 36H 30/0000Z 33.6N 74.4W 35 KT 40 MPH 48H 30/1200Z 34.2N 75.0W 35 KT 40 MPH 72H 31/1200Z 36.5N 73.0W 35 KT 40 MPH 96H 01/1200Z 39.0N 66.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 02/1200Z...DISSIPATED $$ Forecaster Brennan
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