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Tropical Storm Harvey Forecast Discussion Number 9
2017-08-19 16:49:59| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sat Aug 19 2017 000 WTNT44 KNHC 191449 TCDAT4 Tropical Storm Harvey Discussion Number 9 NWS National Hurricane Center Miami FL AL092017 1100 AM AST Sat Aug 19 2017 Harvey has become less organized in visible imagery since this time yesterday, with the convective pattern becoming elongated and the circulation looking less well defined. In addition, an Air Force Reserve Hurricane Hunter aircraft could not close the circulation at 850 mb, but was able to close the circulation at 1000 ft. The plane has not yet reported tropical-storm-force winds, but the northwestern quadrant was not well sampled. Thus, the initial intensity is held at a possibly generous 35 kt. The initial motion is now 275/19. A low- to mid-level ridge extending across the western Atlantic should keep Harvey on a fast westward course across the Caribbean Sea for the next 36-48 hours. Thereafter, there should be a weakness in the ridge north of Harvey caused by a strong mid/upper-level low currently seen in water vapor imagery over the Gulf of Mexico. This pattern should cause a turn toward the west-northwest and a decrease in forward speed. The track guidance is in good agreement that Harvey should pass near or just north of northeastern Honduras, and then cross Belize and/or the Yucatan Peninsula into the Bay of Campeche, and based on this the new forecast track follows the guidance with only minor changes from the previous track. The ongoing moderate vertical shear should continue for another 12-24 h or so, and combined with the current lack of organization should allow at best only slow strengthening. After that, the upper-level winds are expected to become favorable for strengthening as the system moves over the deep warm waters of the western Caribbean. The intensity forecast follows the previous forecast in calling for a peak intensity of 60 kt just before the system reaches Belize or the Yucatan Peninsula. Harvey should weaken as it crosses the southern portion of the Yucatan Peninsula between 72-96 h, followed by some re-intensification over the Bay of Campeche. It should be noted that any additional loss of organization in the next 12-24 h would result in the cyclone degenerating into an easterly wave. FORECAST POSITIONS AND MAX WINDS INIT 19/1500Z 13.9N 68.1W 35 KT 40 MPH 12H 20/0000Z 14.1N 70.9W 35 KT 40 MPH 24H 20/1200Z 14.4N 74.9W 40 KT 45 MPH 36H 21/0000Z 14.9N 78.7W 45 KT 50 MPH 48H 21/1200Z 15.7N 82.4W 50 KT 60 MPH 72H 22/1200Z 17.5N 88.0W 60 KT 70 MPH 96H 23/1200Z 19.0N 91.5W 30 KT 35 MPH 120H 24/1200Z 19.5N 93.5W 40 KT 45 MPH $$ Forecaster Beven
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