A Tropical Storm Threat For Hawaii?

Jon Erdman
Published: July 6,2015
The Western Pacific Basin has roared back to life, with three tropical cyclones, one of which is headed for landfall late this week.
Now, Hawaii needs to pay attention.
(MORE: Hurricane Season Outlook | Hurricane Central | Tropical Update)
A broad area of low pressure, Invest 96E, is about 1,450 miles east-southeast of the Hawaiian Islands.
(MORE: What is an "Invest"?)
So far, thunderstorms have not been able to concentrate and persist to begin the process of tropical cyclogenesis. In other words, we do not yet have a tropical depression.

Enhanced Satellite

However, forecasters at the National Hurricane Center say a generally favorable environment could allow this disturbance to develop in the next few days.
A NOAA Gulfstream jet is tentatively scheduled to sample the environment around the disturbance Tuesday to help computer model forecasts.
If this system becomes a tropical storm – maximum sustained winds at least 39 mph – its name would depend on what side of 140 degrees west longitude this occurs.
This is the case since the National Hurricane Center in Miami issues advisories on all eastern Pacific tropical cyclones, while the Central Pacific Hurricane Center in Honolulu has jurisdiction from 140 degrees west longitude to the international dateline.
If it happens to the east of that line, it would get an eastern Pacific name, Dolores, and keep that name along its track.
Otherwise, it would get the next central Pacific name,  Ela.
The Air Force Reserve hurricane hunters would then investigate the system Wednesday, if it does indeed develop.

Hawaiian Worry?

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.
Last August, Iselle became only the second tropical storm to landfall on the Big Island dating to 1950, after strengthening to a Category 4 hurricane.
Are we looking at another Iselle this time? In short, it doesn't appear so at this time.
First, an extension of upper-level low pressure currently swirling off the California coast will carve southwestward over the next several days, eventually taking it over Hawaii.
The winds aloft from this so-called "tropical upper-tropospheric trough," or TUTT, should have two impacts on the tropical system as it approaches:
1) Hostile wind shear – changing wind direction and speed with height – which tends to displace thunderstorms from the core of a tropical cyclone, limiting its strengthening potential.
2) Steering winds that would deflect the tropical system, assuming it becomes deep enough a circulation, to the north of the Hawaiian Islands.

Late-Week Steering Scenario

But it's still early and this forecast could change.
Furthermore, as noted by Eric Blake, hurricane specialist with the National Hurricane Centerm sea-surface temperatures near Hawaii have set records in June.
All other factors being equal, a warmer sea-surface adds instability to the lower levels of the atmosphere, making a more ripe environment for thunderstorms helping to organize, intensify and sustain a tropical cyclone.
Interests in Hawaii should continue to monitor the progress of this system this week.
(FORECASTS: Honolulu | Hilo | Kona Coast | Maui)
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.
This disturbance may not be the season's last to gain Hawaii's attention.
NOAA's 2015 central Pacific hurricane season outlook cited El Nino'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.
MORE: Hurricanes By the Numbers (PHOTOS)