TROPICAL STORM GONZALO DISCUSSION NUMBER
5 NWS NATIONAL HURRICANE CENTER MIAMI FL
AL082014 1100 AM AST MON OCT 13 2014
An Air Force Reserve reconnaissance aircraft investigating Gonzalo this morning found 850 mb maximum flight-level winds of 64 kt along with reliable SFMR surface winds near 55 kt in the northeastern quadrant, plus a central pressure of 992 mb. In addition, the Antigua-Barbuda Meteorological Service recently reported a sustained wind of 58 kt and a gust to 76 kt. Based on these data, the intensity has been increased to 55 kt. Reports from the aircraft radar and Antigua-Barbuda also indicate the center of Gonzalo passed over Antigua between 1300-1400 UTC.
The initial motion estimate is 290/9 kt. Gonzalo is expected to continue to move west-northwestward today, and turn toward the northwest after 24 hours when the cyclone clears the northern Lesser Antilles. After that, the mid-level ridge to the north of Gonzalo is expected to break down as a strong mid-latitude trough moving off of the U.S. east and southeast coasts approaches the area north of Puerto Rico and Hispaniola in about 72 hours. The weakening ridge will allow Gonzalo to move slowly northward, and then turn toward the northeast and accelerate on Days 4 and 5. The latest NHC model guidance appears to have stabilized and has no longer made any eastward shifts, so the official forecast track is just an update of the previous advisory track, which lies close to a blend of the GFEX and TVCN consensus models.
The satellite presentation of Gonzalo has continued to improve, and radar data from Guadeloupe indicates that a small but intense vortex may have passed over Antigua earlier this morning. Overall, the improvement in the horizontal and vertical structure of Gonzalo the past several hours, along with weak vertical wind shear and SSTs greater than 29C, should allow for at least steady strengthening of the cyclone through the next 96 hours. By 120 hours, southwesterly wind shear of around 20 kt is expected to affect Gonzalo, which should induce a slow weakening trend. The NHC intensity forecast is similar to the previous forecast and the SHIPS intensity model.
Gonzalo is forecast to be reaching hurricane strength by the time it passes near the British Virgin Islands, and so a hurricane warning is in effect there. Although hurricane conditions are not currently expected in the U.S. Virgin Islands, only a slight deviation to the left of the forecast track, or a more rapid strengthening of the storm, would result in the need to extend the hurricane warning into those areas. Interests in the hurricane watch area are reminded that the watch means that hurricane conditions are possible...and in this case within 24 hours.