Update at 11:15 am ET: Hurricane Iselle has weakened only slightly on Thursday morning, and now has maximum sustained winds of 80 mph. Iselle is still expected to be near hurricane status as it makes landfall on the Big Island Thursday night.

Original post:

On Wednesday evening, a hurricane warning was issued for Hawaii for the first time in 22 years. Despite signs that the hurricane was weakening, Iselle strengthened slightly on Wednesday and is now forecast to hit the Big Island as a Category 1 hurricane on Thursday.  If it does so, this will be the first hurricane landfall on the Big Island in recorded history.

As of the 2 a.m. Hawaii time advisory, Iselle still has 85 mph sustained winds and was located 350 miles east-southeast of Hilo.  Landfall is expected later this evening, Hawaii time, or in the early morning hours of Friday, Eastern time.  The impacts will likely be severe for two reasons: it’s a hurricane with destructive winds and a massive amount of rain, and the infrastructure in Hawaii is not designed for such conditions since they occur so infrequently.

Hawaii’s Big Island is home to Mauna Loa and Mauna Kea, the former rising to an elevation of nearly 14,000 feet.  As with any mountainous area, this storm will generate a LOT of rain which will result in flash flooding and mudslides.  Rainfall totals of six to 12 inches will probably not be uncommon, and isolated areas near the highest terrain could see up to 24 inches of rain.  The higher elevations will also experience the strongest winds.  Long radar loops are available to help monitor the storm as it approaches.

Forecast track, watches, and warnings as of the 11 p.m. Hawaii time advisory. (NOAA)

Combing through the records, which extend back to 1950 in the central Pacific, there have been 26 tropical cyclones to pass within three degrees (a little over 200 miles) of the Hawaiian Islands as a tropical storm or hurricane; 12 of those were hurricanes.  Only two hurricanes have technically made landfall on any of the islands: Dot in 1959 hit Kauai as a Category 1 and Iniki of 1992 also hit Kauai as a Category 4.  Iselle will likely be the third hurricane landfall for the state, but the first for the Big Island.  The only other tropical cyclone landfall recorded for the Big Island was a tropical storm in 1958, though others have passed nearby and caused damage via wind and rain.

Tracks of all known tropical storms and hurricanes to pass within three degrees of the Hawaiian Islands (since 1950). There are 26 storms, 12 of which were hurricanes. (NOAA)

Aside from Iselle, there is a lot of action in the Pacific.  Typhoon Halong is still heading for Japan in the West Pacific, Genevieve has rapidly intensified from a tropical depression to a super typhoon over the past couple of days, and Julio is a category 2 hurricane that is also heading toward Hawaii.

Before Genevieve crossed the date line, Phil Klotzbach at Colorado State pointed out that it was the first time that we had three hurricanes at the same time between 130-180°W.  The tropical cyclone activity in this region is likely enhanced by an El Niño starting to shape up.

Infrared satellite image of Genevieve, Iselle, and Julio at 7:15am EDT today. (NASA)
Infrared satellite image of Genevieve, Iselle, and Julio at 7:15 a.m. ET today. (NASA)

Julio, which is a category 2 hurricane on Thursday morning, is intensifying and heading toward Hawaii as well, but will likely skirt the islands to the north.  Some of Julio’s impacts will be felt on the Hawaiian islands, but they won’t be as bad as Iselle.

The last time two tropical storms passed near Hawaii in the same year was 1983 (Narda and Gil), but they were nearly two months apart — not three DAYS!  Two hurricanes have never affected Hawaii in the same year, and probably won’t this year either, given Julio’s forecast to weaken as it approaches the islands.

Hurricane Julio’s track forecast. (NOAA)

Though it won’t affect land, Super Typhoon Genevieve is also extremely interesting. It formed 13 days ago well east of Hawaii, but struggled to maintain itself until just recently.  Maximum winds increased from 35 mph to 160 mph in just 48 hours, and it’s still intensifying.  Genevieve will be around for at least another five days, and will have passed through three different tropical cyclone basins (East Pacific, Central Pacific, and West Pacific).

Infrared satellite image of Super Typhoon Genevieve as of 7:30 a.m. ET. (NOAA)
State officials warn of potential flash floods, mudslides, and power outages from two hurricanes expected to hit Hawaii over the next several days. (Reuters)