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| #873077 (Received by flhurricane at: 4:55 AM 27.Aug.2016) TCDAT2 TROPICAL STORM GASTON DISCUSSION NUMBER 19 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072016 500 AM AST SAT AUG 27 2016 Recent microwave data indicate that Gaston's center is now well embedded near the middle of the central dense overcast. The microwave images also show that a partial mid-level ring has formed, but it remains open to the north-northeast. Even though Gaston's structure appears to be improving, the maximum winds remain 55 kt based on Dvorak Current Intensity numbers from TAFB and SAB. Two outflow jets are emanating away to the east and southwest of Gaston, but the outflow remains restricted to the south and northwest. Still, the shear has decreased substantially from what it was a day or two ago, and it should remain generally low for the next 48 hours. In addition, sea surface temperatures ahead of Gaston are expected to be at least 28C for several more days. Therefore, strengthening is anticipated through day 3, followed by gradual weakening on days 4 and 5 due to increasing westerly shear. Although the intensity models all agree on this general scenario, there is a little more spread in the peak intensities than has been noted in previous advisories. On the high end, the Florida State Superensemble still shows Gaston approaching major hurricane intensity, while the LGEM model is at the other extreme being about 20 kt lower. The updated NHC intensity forecast is near the middle of the guidance and ends up just a little lower than the previous forecast. Gaston is moving northwestward, or 310 degrees at 13 kt, between a mid-tropospheric high to its northeast and a mid-/upper-level low to its southwest. The cyclone is expected to maintain a northwestward heading but steadily decelerate during the next 48 hours. After that time, Gaston should recurve sharply east-northeastward and accelerate through the end of the forecast period as it gets picked up by the mid-latitude westerlies. The track guidance has trended westward through 48 hours, delaying Gaston's recurvature just a bit, and it is then a little faster by days 4 and 5. The NHC track forecast has been adjusted accordingly and is close to the TVCN multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 27.9N 52.0W 55 KT 65 MPH 12H 27/1800Z 28.8N 53.6W 60 KT 70 MPH 24H 28/0600Z 29.9N 55.0W 70 KT 80 MPH 36H 28/1800Z 30.6N 56.0W 80 KT 90 MPH 48H 29/0600Z 31.2N 56.8W 85 KT 100 MPH 72H 30/0600Z 32.5N 55.6W 90 KT 105 MPH 96H 31/0600Z 34.5N 50.5W 85 KT 100 MPH 120H 01/0600Z 37.0N 43.5W 75 KT 85 MPH $$ Forecaster Berg |