Darby Makes the Closest Pass to Honolulu by a Tropical Storm in Recorded History

The closest approach on record by a tropical storm to the island of Oahu resulted in torrential rains in excess of ten inches there as Tropical Storm Darby passed just 40 miles to the south and west of Honolulu, Oahu on Sunday with sustained winds of 40 mph. No other named storm on record has passed that close to Honolulu or Oahu since accurate records began in 1949. Rainfall amounts of over ten inches in the 24 hours ending at 3:45 am HST Monday were reported at five locations on the eastern half of Oahu from Darby:

11.09" Moanalua RG
10.94" Nuuanu Upper
10.81" Luluku
10.70" Waihee Pump
10.04" Palisades

Monday morning Hawaiian radar showed that Darby continued to stream bands of heavy rain over the island, and satellite loops showed that Darby still had plenty of heavy thunderstorms on the northeast side of its circulation. Over the weekend, Darby also brought rains in excess of ten inches to West Wailuaiki, Maui (12.63") and Paauilo, on the Big Island (10.19"). There have been several road closures on Oahu due to flooding, and as of 10 pm HST Sunday, the Honolulu fire department reported 59 calls from residents who needed to be evacuated from their homes due to flooding. About 1,000 customers have lost power from the storm thus far. Darby, downgraded to a tropical depression at 11 am EDT Monday, should cease deluging Oahu by Monday afternoon as the storm pulls away to the west.


Figure 1. Radar-estimated precipitation from Tropical Storm Darby as of 10:53 am EDT (14:53 UTC) Monday, July 25, 2016. A band of heavy 6 - 11" rains fell just east of Honolulu on Oahu Island in Hawaii.


Figure 2. Tracks of all tropical cyclones (tropical depressions, tropical storms, and hurricanes) to pass within 100 miles of the Hawaiian Islands, 1949 - 2016. No named storm at tropical storm strength has passed closer to Honolulu and Oahu in recorded history than Darby, though Raymond hit the island as a tropical depression in 1983. Image credit: NOAA/CSC.

Direct hits by tropical storms and hurricane are uncommon in Hawaii
Darby made a direct hit on the Big Island of Hawaii on Saturday, becoming just the fifth named storm since 1949 to make landfall on a Hawaiian Island. The others were:

Tropical Storm Iselle, which made landfall along the southeast shore of Hawaii's Big Island on August 8, 2014 as a tropical storm with 60 mph winds. Iselle killed one person and did $79 million in damage.

Hurricane Iniki, which hit Kauai as a Category 4 hurricane, killing 6 and causing $1.8 billion in damage (1992 dollars.)

Hurricane Dot, which hit Kauai as a Category 1 hurricane, causing 6 indirect deaths and $6 million in damage (1959 dollars.)

An unnamed 1958 storm that had sustained winds of 50 mph at landfall on the Big Island. The storm killed one person and caused $0.5 million in damage.

Hawaii has seen a lot of activity over the past three years, which may be a harbinger of things to come--see my August 2014 post, Climate Change May Increase the Number of Hawaiian Hurricanes.

Eastern Pacific gets its third major hurricane of the year: Georgette
We're not even into August, and the Eastern Pacific has already had as many major hurricanes as it typically gets in an entire year: three. Hurricane Georgette, which topped out as an impressive Category 4 storm with 130 mph winds on Monday morning, is the latest addition to the club. Georgette is the seventh named storm to form in the Eastern Pacific this month, tying the July record for named storms set in 1985. Since July 2, we've had Tropical Storm Agatha, Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, Tropical Storm Estelle, Tropical Storm Frank and Category 4 Hurricane Georgette. This puts us well ahead of climatology: the Eastern Pacific usually does not see its seventh named storm until August 7, its fourth hurricane until August 12, and its third major hurricane until September 20. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes.


Figure 3. VIIRS visible satellite image of Tropical Storms Frank (right) and Hurricane Georgette (left) taken at 5:20 pm EDT Sunday July 24, 2016. At the time, Georgette was an intensifying Category 2 storm with 105 mph winds. Image credit: NASA.

The Atlantic is still quiet
There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. A few recent runs of the GFS model have been highlighting the possible development this weekend of a tropical wave predicted to come off the coast of Africa around July 27. The 00Z Monday run of the GFS ensemble forecast had about 30% of its twenty ensemble members predict that a tropical depression would form this weekend or early next week midway between Africa and the Lesser Antilles. Most of these forecasts had the storm dying out the middle Atlantic, due to unfavorable conditions. There will be several impressive pulses of dry air and dust coming off the Sahara Desert over the next ten days, which will likely make it challenging for any tropical waves to develop (check out this animation of the 10-day African dust forecast from NASA.) Less than 10% of the 50 members of the 00Z Monday European model forecast showed a tropical depression forming in the Atlantic over the next ten days. I'm not expecting to see anything form in the Atlantic until August.

Jeff Masters