| Category 4 hurricane (SSHS) | |
|---|---|
| Hurricane Flossie on August 11 | |
| Formed | August 8, 2007 |
| Dissipated | August 16, 2007 |
| Highest winds | 1-minute sustained: 140 mph (220 km/h) |
| Lowest pressure | 949 mbar (hPa; 28.02 inHg) |
| Fatalities | None reported |
| Damage | Minimal |
| Areas affected | Hawaiʻi |
| Part of the 2007 Pacific hurricane season | |
Hurricane Flossie was a strong Category Four Hurricane which brushed the island of Hawaiʻi as it rapidly weakened to a tropical storm. Flossie was the ninth tropical cyclone and sixth named storm of the 2007 Pacific hurricane season. Flossie developed from an ill defined wave which formed off the coast of Africa on July 21 and traversed the Atlantic. The wave crossed into the Pacific on August 2 while remaining poorly organized. The low slowly developed over the next few days before gaining enough convection to be declared a tropical depression on August 8. The depression quickly strengthened to a tropical storm early the next morning and later to a hurricane on August 10. Flossie became a major hurricane on August 11 and reached category four status just before entering the Central Pacific basin later that day. Flossie maintained a category four until August 14 when vertical wind shear increased and began to weaken the system. Flossie brushed the southern coast of Hawaiʻi as the strong wind shear took its toll on the storm. Flossie dissipated on August 16 as it moved away from the islands without making landfall.
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A poorly organized tropical wave moved off the African coast on July 21 into the Atlantic Ocean. The wave produced very little convection as it moved towards the west. On August 1, the wave crossed over Central America and entered the Pacific the next day. The low continued to produce very little convection for the next few days. On August 4, there was some increase in convection but not much. Two days later, there was a large increase in convection and the low was near tropical depression strength. However, the convection did not persist and the system weakened slightly. On August 8, the system had reorganized and gained stronger convection which persisted and the low was declared Tropical Depression 09-E later that night.[1][2]
The depression was located in an environment of low wind shear and warm sea surface temperatures, favorable for intensification, and was quickly upgraded to Tropical Storm Flossie on its second advisory.[1][3] Flossie gradually intensified and was upgraded to a hurricane on August 10 as an eye began to form. Forecasts showed that Flossie would intensify some more before entering an area that was less favorable for development which would get less favorable towards the end of the forecast period.[4] Flossie intensified further to a strong Category One shortly after and the peak intensity in the forecast was increased to a low end Category Two.[5]
That night, Flossie's eye became more well defined and cleared out as the storm rapidly intensified to a major hurricane as it moved out of the National Hurricane Center's area of responsibility.[6] Flossie continued to rapidly intensify and reached Category Four status shortly after entering the Central Pacific. Forecasts showed the intensification ending and that colder water and stronger shear would begin to weaken the system in 24 hours.[7] Flossie maintained its intensity as it continued its westward movement. The possibility of a Hawaiʻian landfall was beginning to unfold as Flossie neared the big island.[8] Flossie again intensified slightly, with winds reaching 140 mph (230 km/h).[9] Despite days of predictions to the contrary, the storm did not lose intensity,[10] leading a forecaster at the CPHC to remark that "Hurricane Flossie is not willing to give up."[11]
On the morning of August 13 Hurricane Flossie began to weaken[12] as wind shear, upper-level warming, and restricting outflow finally began to take their toll.[13] By that night the storm's central pressure had risen to 970 mb[14] and the persistent upper-level wind shear caused breaks in the southeast eyewall which preceded the eye's eventual collapse.[15] Although the eye had disappeared from satellite imagery, NEXRAD and reconnaissance data on August 14 showed a partial eyewall open to the southeast.[16] 29 mph (47 km/h) southwesterly wind shear decimated the storm's structure and restricted outflow, further weakening it.[17] Satellite imagery showed portions of the eyewall uncovered again, and land-based radar showed an absence of deep convection in the southeast semicircle.[18] Under the effects of the negative environmental conditions, Flossie's eye disappeared again,[19] and Flossie weakened to a tropical storm late that night local time.[20] The last advisory was issued on August 16.[20]
The CPHC issued a hurricane watch on August 13 for the Big Island of Hawaii as the storm neared the islands without weakening significantly.[21] Later, as the hurricane tracked slightly further to the north and its wind radii expanded, a tropical storm warning was issued for the same areas as the hurricane warning.[22] Heavy rainfall and flooding were expected to be the primary concern, and as such, flash flood watches were issued, with 10 to 15 inches (250 to 380 mm) of rainfall considered possible. Also, tropical storm-force winds were expected.[23] Governor Linda Lingle declared a state of emergency for the Island of Hawaii, where residents were advised to stock up on necessary supplies.[24]
The Federal Emergency Management Agency (FEMA) dispatched 20 transportation, public works and health experts to the region. Emergency shelters were opened, though were used little.[25] The threat of the storm forced the closure of schools, including the University of Hawaii at Hilo and Hawaii Community College. Some libraries, parks, private schools, banks and other businesses were also closed. Non-essential state employees were advised to remain at home,[26] and emergency workers were mobilized.[27] In advance of the storm, many tourists canceled reservations.[28]
Forecast heavy rains over the southeast-facing slopes of the Big Island failed to occur, as Flossie turned away before low level southeasterly winds had a chance to produce mountain-enhanced rainfall. However, north- and east-facing slopes received some rainfall; 1 to 2 inches (0.025 to 0.051 m) of rain was reported in the Hamakua, South Hilo, and Puna Districts. Elsewhere, 1 to 3 inches (25 to 76 mm) of precipitation fell at Maui, and 2 to 4 inches (51 to 100 mm) fell at the Koolau Range on Oahu, although no significant winds or flooding was reported. Wave action affected the southeast-facing shores, also with little impact.[29] The most significant waves were estimated at 20 feet (6.1 m) in height, while sustained winds of at least 39 miles per hour (63 km/h) were reported at South Point. A large lava bench collapsed into the ocean on August 13, which may have been related to the hurricane's passage, or alternatively, a recent earthquake.[30]