Sunday, July 28, 2013

Flossie Moves Towards Hawaii

Tropical Storm Flossie is pushing along to the west, about 36 hours or so away from impacting parts of the Hawaiian Islands. The storm sports a max wind of 60 mph but is generally forecast to gradually weaken as the storm approaches the islands.  That said, Flossie should be able to bring some heavy rain and some wind to parts of Hawaii as it moves through Monday.

Tropical Storm warnings are up for the southeast half of the island chain.  It is expected to weaken due to the combination of expected northerly wind shear and dry air aloft that will eat away on the storm.  The northerly wind shear is expected to become an increasing factor later Monday into Tuesday, which would work to weaken the storm and probably dissipate it once Flossie passes Hawaii by.  Ocean temperatures are marginal to the east of Hawaii (better to the west) but the shear/dry air combo will work to effectively knock this storm out after it moves through.

Hawaii normally doesn't get many tropical storms that cross the islands from the east.  This graphic above shows the tracks of tropical systems through 1997 that have impacted Hawaii. There have been a few storms that have skirted along to the north (Hiki is one, Fernanda is a second example), some that have skirted to the south that have been hurricanes as they have done so (Flossie in 2007 is an example and there are others) but very few survive a trek towards Hawaii from the east due to cooler ocean and often unfavorable winds aloft across this portion of the Pacific.  Hawaii does occasionally get impacted by the dying remnants of these storms, passing through as rain makers, but the big league wind and destruction that is often associated with hurricanes occurs when hurricanes track towards Hawaii from the south (Iniki in 1992, Dot in 1959, and Iwa in 1982 are three examples).

Flossie will provide potentially five to ten inches of rain across the islands of Hawaii and Maui, with isolated higher amounts along the eastern-facing mountains that squeeze out additional tropical moisture. Winds will not be a huge factor but it is a pretty unique experience to see a tropical system come in at them from the east.  It doesn't happen, as a named storm, all that often.