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| #1015767 (Received by flhurricane at: 10:57 PM 08.Sep.2020) TCDAT3 Tropical Depression Rene Discussion Number 8 NWS National Hurricane Center Miami FL AL182020 200 AM CVT Wed Sep 09 2020 Rene`s circulation remains fairly robust based on a 08/2148Z ASCAT-A overpass. However, the overall convective pattern has eroded significantly, and this is reflected in the ASCAT scatterometer wind data only showing surface winds of about 25 kt. Allowing for some undersampling, plus a recent increase in convection near the center, the intensity has only been lowered to 30 kt for this advisory. Rene remains beneath a pronounced upper-level anticyclone and outflow is fairly symmetrical in all quadrants. The initial motion is 285/14 kt. There continues to be no significant change to previous forecast track or reasoning. Rene is expected to move generally west-northwestward around the southwestern periphery of a deep-layer ridge for the next couple of days, followed by a decrease in forward speed and a turn toward the northwest on Friday and a motion toward the north on Saturday and Sunday. The latest NHC model guidance is in decent agreement on this developing steering flow pattern, thus the new NHC track forecast is essentially just an extension of the previous advisory track and lies close to a blend of the consensus models TVCA, GFEX, and NOAA-HCCA. Although Rene has weakened, a burst of strong convection with cloud tops colder than -80C has developed over and to the west of the center, while a fragmented band of convection has formed in the northern semicircle. These features strongly suggest that Rene is poised to restrengthen soon. Sea-surface temperatures are expected to be 26.0-26.5 deg C in the 24-60 h period, which are only marginal for strengthening to occur. However, mid-level humidity values are forecast to be near 70 percent and the cyclone is expected to remain under a favorable upper-level anticyclone during that time. Given these factors, slow but steady intensification is forecast, with Rene still expected to become a hurricane in 2-3 days. Thereafter, strong westerly to west-northwesterly vertical wind shear in excess of 25-30 kt is expected to cause Rene to weaken significantly on days 4 and 5. The new official intensity forecast is similar to but slightly lower than the previous intensity forecast, and is along the extreme upper portion of the guidance envelope and is above the intensity consensus models. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 17.0N 29.3W 30 KT 35 MPH 12H 09/1200Z 17.5N 31.1W 35 KT 40 MPH 24H 10/0000Z 18.4N 33.7W 40 KT 45 MPH 36H 10/1200Z 19.3N 35.9W 50 KT 60 MPH 48H 11/0000Z 20.5N 38.1W 60 KT 70 MPH 60H 11/1200Z 22.1N 39.8W 65 KT 75 MPH 72H 12/0000Z 24.2N 41.4W 60 KT 70 MPH 96H 13/0000Z 28.5N 42.6W 50 KT 60 MPH 120H 14/0000Z 30.2N 40.3W 40 KT 45 MPH $$ Forecaster Stewart |