(ABOVE IMAGE) A National Weather Service image shows the latest 5 day track for Tropical Storm Ana.
- Hawaii County remains under a Tropical Storm Watch
- Tropical Storm Ana is 465 miles southeast of Hilo, Hawaii. The storm is moving west at 8 miles per hour.
- Maximum sustained winds are near 60 miles per hour, with higher gusts. Gradual strengthening is forecast during the next 36 hours, and Ana is forecast to become a hurricane on Friday. Some weakening is expected by 48 hours. Ana is expected to turn toward the west-northwest today, then turn toward the northwest on Friday with a slight increase in forward speed. On the forecast track, the center of Ana will pass near the Big Island Friday night and Saturday.
- Large swells produced by Ana are possible over the eastern end of the main Hawaiian island chain starting late tonight and Friday morning.
As it has been doing for the past couple of days… Ana continues to produce intense bursts of deep convection confined to a limited area. One such burst is currently underway. The latest dvorak current intensity estimates all came in at 3.0/45 kt… With cimss satcon from 1520z estimating 44 kt. Given the current blossoming of deep convection that is underway… The initial intensity will continue to be held at 50 kt.
Due to its continued ragged appearance… The center location continues to pose a challenge. The sab and jtwc fixes put the center a bit east of the hfo estimate… And with the aid of microwave data from 1638 and 1732z… The center position for this advisory has been placed in between the fix agencies to the west of the deep convection. The result is a slight decrease in forward motion… Which is set at 270/07 kt. Ana is expected to take a turn to the west-northwest today then northwest tonight and Friday as the low to mid level ridge to the northeast of Ana shifts to the east as an upper level trough approaches from the northwest. This expected turn to the west-northwest has been slow to develop. As a result… The forecast track has been shifted slightly to the left through 72 hours but still lies on the right edge of the dynamic model and consensus envelope. Given the uncertainty in the 36 hour position… A tropical storm watch will remain posted for the Big Island of Hawaii. The NOAA Gulfstream IV is sampling the environment around Ana today… And the data from this flight should help improve subsequent model guidance. On Sunday… A ridge building north of the cyclone will impart an increasing motion westward… With the timing of the turn having significant implications as to the potential impacts felt on the rest of the main Hawaiian Islands. By day 5… Ana is forecast to be entering the Papahanaumokuakea Marine National Monument… Potentially affecting Nihoa.
Slow intensification is expected through Friday night… As vertical wind shear and ocean temperatures remain conducive. However… Ana has not been able to maintain an effective outflow channel… And with Ana remaining south of the upper level ridge through the next 24 to 36 hours these conditions will likely not change significantly. All guidance except for the hwrf now fail to bring Ana to hurricane intensity… And the current forecast briefly brings the system to a hurricane by Friday night… Followed by weakening as Ana encounters increasing vertical wind shear imparted by an approaching upper level trough.
It is important for people in the main Hawaiian Islands not to focus too closely on the exact forecast track of Ana. With an average 48 hour track error of approximately 80 miles… It is still too soon to say with much certainty which islands will be most likely to experience the worst weather. Everyone should be prepared for the possibility of direct impacts from Ana. It is also important to keep in mind that significant impacts from tropical cyclones can extend well away from the center. National Weather Service discussion on Oct. 16 at 11 a.m. HST