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Tropical Storm Maria Forecast Discussion Number 51
2017-09-28 22:39:33| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Sep 28 2017 000 WTNT45 KNHC 282039 TCDAT5 Tropical Storm Maria Discussion Number 51 NWS National Hurricane Center Miami FL AL152017 500 PM AST Thu Sep 28 2017 After the earlier burst of convection near the center of Maria, the overall convective pattern has become more ragged and cloud tops have warmed. Westerly vertical shear has also displaced most of the convective cloud shield to the east of the center. The most recent Dvorak satellite intensity estimate from TAFB has decreased to 45 kt, and the latest UW-CIMSS ADT and SATCON values have decreased to 54 kt and 55 kt, respectively. Therefore, Maria's initial intensity has been lowered to 55 kt for this advisory. Despite the ragged satellite appearance, a 1431Z AMSU overpass indicated that Maria is still a tropical cyclone based on a deep warm core that extends from near the surface to above the 200 mb level, accompanied by a warm anomaly of at least 2.5 deg C in the middle- and upper-levels of the cyclone. The initial motion estimate is 090/11 kt. Maria is forecast to move in an easterly direction for the next 12 h or along the northern edge of a strong deep-layer ridge located to its south. By 24 h, acceleration and a turn toward the east-northeast is expected ahead an approaching deep-layer trough. By 36-48 h, Maria is forecast to turn toward the northeast and further accelerate, reaching forward speeds of 30-35 kt when the cyclone will be moving over the far North Atlantic. The latest track guidance continues to remain in excellent agreement on this developing track scenario, and only a slight nudge to the south of the previous forecast was required. Little change in intensity is forecast during the next 36 h or so while Maria remains over marginal SSTs of 25-26C and within a low to moderate vertical wind shear environment. By 36 h and beyond, Maria will be moving over sub-24C SSTs, reaching 21 deg C water by 48 h or so. Increasing westerly wind shear of more than 40 kt should induce a slow weakening trend, and Maria is now expected to become extratropical by 48 h due to the aforementioned unfavorable conditions. The extratropical low is forecast to be absorbed by a larger low or frontal system over the northeastern Atlantic by 96 h, before the low moves across Ireland. The intensity and wind radii forecasts at 48 and 72 h are based on guidance provided by the NOAA Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 36.8N 67.8W 55 KT 65 MPH 12H 29/0600Z 37.1N 64.4W 55 KT 65 MPH 24H 29/1800Z 38.1N 58.8W 55 KT 65 MPH 36H 30/0600Z 40.0N 52.0W 55 KT 65 MPH 48H 30/1800Z 42.7N 44.4W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 01/1800Z 48.8N 26.7W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 02/1800Z...DISSIPATED $$ Forecaster Stewart
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