000 WTPZ41 KNHC 100232 TCDEP1 Tropical Storm Adrian Discussion Number 2 NWS National Hurricane Center Miami FL EP012017 1000 PM CDT Tue May 09 2017 Although outer banding features have weakened somewhat since the previous advisory, the inner-core convective pattern has improved, including the possible development of a small, mid-level eye feature as noted in 0059Z SSMI/S microwave data. The upper-level outflow is improving and expanding in all quadrants, except to the east where is being restricted by upper-level easterly flow. Satellite classifications are a consensus T2.5/35 kt from TAFB and SAB, so the depression has been upgraded to tropical storm status. This makes Adrian the earliest tropical storm to form in the eastern North Pacific basin during the satellite era. The initial motion estimate is 290/06 kt. Adrian is moving slowly west-northwestward along the southern periphery of a deep-layer ridge located over the central and southwestern Gulf of Mexico. The global and regional models are fair agreement on this ridge pattern remaining basically static for the next 48-72 hours, so little change in the west-northwestward motion of the tropical storm is expected during that time. By 72 hours and beyond, the ridge to the north of Adrian is forecast to gradually weaken and eventually break down by 120 hours as the large-scale, high-amplitude flow pattern across the United States weakens and shifts eastward. This pattern change is expected to result in weak southwesterly steering flow developing, causing the cyclone to slow down significantly and turn northeastward. The 12Z ECMWF model run does not develop the cyclone beyond its current intensity, which results in a very shallow system being steered northeastward by increasing southwesterly low-level monsoon flow by 72 hours and beyond. This scenario seems unlikely at this time given that Adrian is forecast to strengthen into a hurricane and become more vertically deep, so less weight has been placed on the weaker ECMWF solution. The official forecast track is similar to the previous advisory track, and lies close to a blend of the various consensus models. Earlier scatterometer wind data and recent microwave satellite imagery indicate that Adrian has developed a small radius of maximum winds of 25-30 nmi. This tight inner-core wind field, along with SSTs exceeding 30 deg C, a moist mid-level environment, and only modest wind shear of 10-15 kt support steady intensification throughout the forecast period. By 96-120 hours, increasing southerly to southwesterly vertical wind shear could disrupt the intensification process, but Adrian is expected to already be a hurricane by that time. The official intensity forecast follows the strengthening trend of the previous advisory, but is a little stronger and is similar to the SHIPS model forecast due to the non-development of Adrian noted in the HWRF and Navy COAMPS models, which is causing a low bias in the IVCN/ICON consensus models. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 9.5N 92.3W 35 KT 40 MPH 12H 10/1200Z 9.8N 93.1W 40 KT 45 MPH 24H 11/0000Z 10.3N 94.1W 50 KT 60 MPH 36H 11/1200Z 10.8N 95.2W 55 KT 65 MPH 48H 12/0000Z 11.2N 96.2W 60 KT 70 MPH 72H 13/0000Z 12.1N 97.1W 70 KT 80 MPH 96H 14/0000Z 13.1N 96.8W 80 KT 90 MPH 120H 15/0000Z 14.1N 96.0W 85 KT 100 MPH $$ Forecaster Stewart