Hurricane Hilda heads toward Hawaii
- A tropical storm watch was issued Tuesday morning by the Central Pacific Hurricane Center for the Big Island of Hawaii.
- Hurricane Hilda is holding as a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale with maximum sustained winds of 85 mph as of Tuesday morning, Hawaii time.
- The center of Hilda is about 290 miles east-southeast of Hilo, Hawaii, and is moving slowly northwest.
- Hilda is expected to weaken due to increasing wind shear the next few days.
- The latest thinking suggests a weakened Hilda may move near or either side of the Big Island Thursday, with impacts lingering into Friday. See below for more information on what impacts are likely or possible in Hawaii.
- Hilda reached its maximum intensity as a Category 4 hurricane with top sustained winds of 140 mph late Saturday.
A U.S. Air Force Reserve Hurricane Hunter reconnaissance mission Monday night found Hilda's inner core of convection is still holding firm, despite increased wind shear. Hilda's forward motion has also slowed considerably, and this may continue into Wednesday.
Hilda may still be a hurricane now, but by late this week, it appears it will limp toward Hawaii's Big Island in a much weaker state, either as a tropical depression or a weak tropical storm.
Already a rather small tropical cyclone, Hilda will feel intensifying shearing winds aloft from a strong subtropical jet stream blanketing the Hawaiian Islands and areas to the east of the island chain. Shearing winds push a tropical cyclone's thunderstorms away from its center, weakening it, as we saw with Guillermo last week. Another factor in the expected weakening of Hilda is its slow motion could result in upwelling of colder sub-surface water.
The latest thinking is this wind shear will leave an increasingly shallow circulation of Hilda to migrate west-northwest toward the Big Island of Hawaii Thursday.
With the rate of weakening still a little uncertain, the Central Pacific Hurricane Center hoisted a tropical storm watch for Hawaii County -- the Big Island -- meaning tropical storm-force winds are possible within the next 48 hours.
For now, here are what impacts we're expecting, based on the current forecast:
LIKELY: High surf will continue on east and southeast-facing shores of the Big Island and Maui, reaching a peak by early Tuesday, but persisting at least into early Wednesday, according to the National Weather Service. Waves of up to 8-12 feet and dangerous rip currents are expected.
POSSIBLE: Assuming Hilda doesn't shear apart completely before arriving, locally heavy rain is possible in the Big Island starting as early as Wednesday, perhaps extending into some of the other islands into the weekend. Some gusty winds are possible too, particularly over higher elevations and exposed coastal locations.
(INTERACTIVE: Hawaii Radar)
All interests in the Hawaiian Islands should continue to monitor the progress of Hilda. Tropical storm watches may be posted sometime Tuesday.
Virtually every system approaching Hawaii from the east since 1950 tracking at least as far north as the latitude of the Big Island of Hawaii eventually weakened to a tropical storm or depression by the time it reached the islands.
We discussed the reasoning behind this in a piece written in August 2014.
Incidentally, hurricanes Julio and Ana also passed near the Hawaiian Islands in 2014. Ana was one of only four hurricanes since 1950 to pass within 150 nautical miles of Honolulu, dumping locally heavy rain and generating high surf.
Hurricane specialist Michael Lowry says 17 tropical cyclones of at least tropical storm intensity have tracked within 100 nautical miles of Hawaii dating to 1950. Three of those -- Tropical Storm Flossie (2013), Tropical Storm Iselle (2014) and Hurricane Ana (2014) -- have done so since 2013.
This may not be the season's last named storm to gain Hawaii's attention.
NOAA's 2015 central Pacific hurricane season outlook cited El Niño's tendency for reduced wind shear and more storm tracks coming from the eastern Pacific as reasons to expect an active season in the central Pacific Basin.
Here are the effects of El Niño so far:
Lowry says dating to 1950, there is a 13 percent increase in the chance of a named storm to track within 100 miles of the Hawaii islands during an El Niño year than a neutral year.