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Tropical Storm Hilary Forecast Discussion Number 11
2017-07-24 04:50:31| National Hurricane Center (East Pacific)
Issued at 1000 PM CDT Sun Jul 23 2017 000 WTPZ44 KNHC 240250 TCDEP4 Tropical Storm Hilary Discussion Number 11 NWS National Hurricane Center Miami FL EP092017 1000 PM CDT Sun Jul 23 2017 Hilary has continued to become better organized with a curved convective band now wrapping nearly all the way around the low-level center, and a banding eye of about 10 n mi in diameter evident in recent SSMI/S microwave satellite data. The intensity estimate was 55 kt by TAFB at 0000Z, but since the overall convective and inner-core patterns have improved during the past few hours, the initial intensity is increased to 60 kt for this advisory. The initial motion estimate is 300/08 kt. There is no significant change to the previous forecast track or reasoning. Hilary is expected to move west-northwestward along the southern periphery of a deep-layer ridge to its north for the next several days, with a slight increase in forward speed expected in about 48 hours or so. The new model guidance is tightly packed around the previous NHC advisory track through 96 h, so the new forecast track is just an update of the previous one, and closely follows the HCCA and TVCN models. Given the improving inner-core structure, coupled with very low vertical shear values and a moist unstable environment, continued rapid intensification appears likely for the next 36-48 hours while the small cyclone remains over SSTs greater than 28C. By 72 hours, SSTs cool to near 27C and the upper-ocean heat content decreases to less than 10 units, suggesting that cold upwelling will probably begin around that time. The new intensity forecast follows the previous advisory by showing rapid strengthening of about 15 kt every 12 hours for the next 36 hours, followed by a slightly slower rate of strengthening since an eyewall replacement cycle could begin in the 36-48 h period. After that, increasing shear and cooler water temperatures should induce gradual weakening. The official intensity forecast is similar to the corrected-consensus model HCCA, which brings Hilary to a 116-kt, category-4 hurricane in 48 hours. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 13.6N 103.5W 60 KT 70 MPH 12H 24/1200Z 14.0N 104.5W 70 KT 80 MPH 24H 25/0000Z 14.7N 106.0W 85 KT 100 MPH 36H 25/1200Z 15.4N 107.6W 100 KT 115 MPH 48H 26/0000Z 16.1N 109.5W 110 KT 125 MPH 72H 27/0000Z 17.2N 113.4W 105 KT 120 MPH 96H 28/0000Z 18.3N 117.1W 90 KT 105 MPH 120H 29/0000Z 19.2N 120.8W 80 KT 90 MPH $$ Forecaster Stewart
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