(ABOVE IMAGE) A National Weather Service image shows the latest 5 day track for Tropical Storm Ana.

NEWS BRIEFS

• Hawaii County remains under a Tropical Storm Watch
• Tropical Storm Ana is 500 miles southeast of Hilo, Hawaii. The storm is moving west at 10 miles per hour.
• Maximum sustained winds are near 60 miles per hour, with higher gusts. Ana is forecast to gradually intensify and is still predicted to become a hurricane on Friday. Ana is expected to turn toward the west-northwest today, then turn toward the northwest on Friday with little change 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.

PRIMARY SOURCES

The outflow pattern associated with ana has improved over the past several hours… Especially in the northern semicircle… Indicating what appears to be a relaxation of the moderate shear that has been plaguing the system over the past 24 to 36 hours. Although the system continues to present a somewhat ragged appearance in satellite imagery… A burst of deep convection has recently blossomed and persisted near the assumed center. Latest dvorak current intensity estimates are a consensus 3.0/45 kt… But given the new convection… The initial intensity for this advisory is determined to be the same as the previous…50 kt.

With limited microwave passes over the past couple of hours… Locating the low level center has been a bit of a challenge overnight. A recently received 1120 utc gcom overpass helped to some degree… But this occurred just before the burst of new convection began. The center is assumed to be just west of the deepest convection… Resulting in an initial motion estimate of 265/09 kt. Latest track guidance continues the trend presented by earlier runs… Thus the updated track forecast offers little in the way of significant changes. The forecast lies within a tightly clustered guidance envelope… Especially through day 3… And is close to the previous track… And the tvcn consensus. Both the 06 utc gfs and 00 utc ecmwf runs indicate that Ana will begin to move along a west-northwest trajectory later today into tonight… And then move along an increasingly northwesterly track Friday and Saturday. On this track… The center will pass southwest of the Big Island Friday night… And close to Oahu, Kauai and Niihau over the weekend. On Sunday… A ridge building north of the cyclone will impart an increasingly westerly motion… With the timing of the turn having significant implications as to the potential impacts felt on those islands. By day 5… Ana is forecast to be entering the Papahanaumokuakea Marine National Monument… Potentially affecting Nihoa.

Sufficiently warm water temperatures and an expected short term decrease in vertical wind shear supports intensification to a hurricane over the next 24 to 36 hours… In line with the latest hwrf guidance. However… Ships and lgem do not anticipate hurricane development and depict only modest intensification through 36 to 48 hours… Before increasing wind shear leads to weakening on days 3 through 5 despite increasingly warm water temperatures. The recent observed trends support gradual intensification… And the forecast represents a blend of the guidance… Delaying hurricane development until Friday.

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 5 a.m. HST