(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 340 miles south southeast of Hilo, Hawaii. The storm is moving west northwest at 14 miles per hour, a direction that is expected to continue tonight, with a slight turn to the northwest on Friday and Saturday. A decrease in forward speed is expected on Saturday.
• Maximum sustained winds are near 65 miles per hour, with higher gusts. Gradual strengthening is expected during the next 24 hours, with Ana possibly becoming a hurricane on Friday. Slight weakening is expected on Saturday. Tropical storm force winds extend outward up to 70 miles

PRIMARY SOURCES

Ana has been producing persistent deep convection near the center since this morning… With an increasingly impressive outflow pattern observed in latest satellite images. Dvorak intensity estimates are 3.0/45 kt from phfo and sab… While pgtw derived 3.5/55 kt. However…0055z ssmi and 0349z ssmi/s overpasses depicted structure consistent with that of a system nearing hurricane strength… With a partial eyewall detected east of the center. Based on a blend of this data… The initial intensity for this advisory has been increased to 55 kt. A U.S. Air Force reconnaissance aircraft is in transit from the mainland… And is expected to provide critically valuable data regarding storm structure for the next forecast package… After the NOAA g-iv sampled the near storm environment earlier today.

The turn toward the west-northwest that began earlier today continues this evening… With an initial motion estimate of 295/12 kt. A gradual turn toward the northwest is expected late Friday and Saturday… As the deep layer anticyclone centered to the northeast of Ana is nudged eastward by a mid-latitude trough passing north of the Hawaiian Islands. Late Saturday and Sunday a new ridge is forecast to build north of Ana… Resulting in a slowing in the forward motion… And a turn toward the west… Just as the system approaches Kauai County and Oahu from the south. The timing and extent of this turn has significant implications as to the potential impacts in the islands this weekend. The latest forecast track follows the previous forecast closely… And is in line with most of the dynamic guidance in the short term… And lies on the right side of most guidance at the longer time ranges. By days 4 and 5…Ana is forecast to be near the Papahanaumokuakea Marine National Monument.

Modest intensification is expected through Friday… As vertical wind shear has decreased… And is expected to remain rather light through Friday night… While water temperatures will be efficiently warm to support development. This is expected to allow Ana to strengthen to a hurricane in the short term. The window for strengthening is expected to close on Saturday… At least temporarily… As the passing mid-latitude trough imparts increased vertical wind shear. The official forecast follows the trends presented by ships and lgem during this weakening phase. Worth noting that some models show another strengthening trend as Ana reaches the anomalously warm waters northwest of the main Hawaiian Islands toward the end of the forecast period. This variance is due to differences in the magnitude of the forecast wind shear near the system.

It is important for everyone to understand that the exact track that Ana takes will be critical to the sensible weather and water impacts that the main Hawaiian Islands will have to endure. Unfortunately it is still too soon to try to nail down details… Particularly for the smaller islands. If the center of Ana tracks more toward the right side of the error cone… The result would be drastically worse weather than a track on the left side. National Weather Service discussion on Oct. 16 at 11 p.m. HST