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Hilda Fizzling as it Approaches Hawaii; Twin Typhoons Coming to the Western Pacific

By: Jeff Masters 3:29 PM GMT on August 13, 2015

The Tropical Storm Watch for the Big Island of Hawaii has been dropped as Tropical Storm Hilda heads westwards at 9 mph on a course that will take it no closer than 150 miles south of the Big Island. High wind shear of 30 - 40 knots continues to disrupt Hilda, and satellite loops on Thursday morning showed the storm struggling to keep a respectable amount of heavy thunderstorm activity near its core. Shear will remain a high 25 - 40 knots through Friday, the surrounding atmosphere will grow increasingly dry, and sea surface temperatures will cool slightly, which should cause Hilda to weaken to a tropical depression on Friday, if not sooner. However, even if Hilda dissipates before reaching Hawaii, it will still be capable of bringing heavy rains to the islands, particularly to the Big Island. The 2 am EDT (06Z) Thursday run of the HWRF model predicted that the eastern portion of the Big Island would see 4 - 8" of rain over the next few days from Hilda, with the southern portion of Maui receiving 2 - 4". Rains of this magnitude will be capable of causing dangerous floods and mudslides. Hawaii could use some rain, though--today's Drought Monitor classified 26% of the state as being in moderate or greater drought.

Figure 1. When a hurricane unravels: high wind shear due to strong upper-level westerly winds on Wedneday, August 12, 2015, exposed the low level center of Hurricane Hilda to view. Hilda's heavy thunderstorms were all on the east side of the center of circulation in this MODIS satellite image from approximately 9 pm EDT, when Hilda had top winds of 45 mph. Image credit: NASA.

Twin typhoons likely next week in the Western Pacific
In the Western Pacific, a pair of tropical disturbances, 97W and 98W, appear destined to become twin typhoons early next week, according to the latest runs of the European and GFS models. Both of these storms will have the potential to cause trouble for Asia late next week. The twin storms will be close enough together that they could influence each other, making prediction of their track and intensity more difficult than usual.

Figure 2. Surface winds over the Pacific Ocean on Thursday morning, August 13, 2015. Image credit: http://earth.nullschool.net/.

Ten years ago today
Tropical Depression Ten formed on August 13, 2015, from a tropical wave that emerged from the west coast of Africa on August 8. As a result of strong wind shear, the depression remained weak and did not strengthen beyond tropical depression status, and degenerated on August 14. Its remnants partially contributed to the formation of Tropical Depression Twelve, which eventually intensified into Hurricane Katrina. Thanks go to wunderground members MonsterTrough and BiloxiIsle for posting this in my blog comments.

The Atlantic remains quiet today, with no tropical cyclone development likely over the next five days.

Bob Henson will have a new post by 2 pm EDT this afternoon on the latest monthly El Niño update issued by NOAA.

Jeff Masters


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