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Nov
07
2011

Hawaii Weather Overview


Hawaii Weather Synopsis: An upper level low near the state will keep unsettled weather for much of this week. Showers will be focused across windward and mauka areas, but will also spread leeward at times. A strong high pressure system will pass to the north during the middle of this week and bring windier conditions.

A Small Craft Advisory is in effect until 6 am HST Tuesday for Maalaea Bay, Pailolo channel, Alenuihaha channel, Big Island leeward waters, Big Island southeast waters.

 

PDC Global Hazards Atlas showing the Hawaiian Islands with TRMM 3-hour precipitation accumulations.

 

Click on the following link for the latest National Weather Service advisories and warnings: Wind/Surf/Flood related advisories or warnings

Broad Overview of Hawaii’s Weather

Based on the NWS Area Forecast Discussion for Hawaii, issued 7 Nov 2011 at 1000am HST  

Water vapor imagery shows an upper level low just south of the state. Infrared satellite images from early this morning showed some mid-level clouds over Maui County – a sign of the elevated instability – but these have thinned out following sunrise.

An area of low-level moisture just upstream of the smaller islands will move through today, with a patch of drier air behind it. Rainfall amounts were generally 0.1-0.2 inches for the 12-hour period ending at 8 am HST, with the exception being Kauai where amounts ranged up to 0.3-0.6 inches. The GFS model shows drier low-level air spreading across the state this afternoon, which will lower shower coverage.

By the middle of the week, models show the upper low building westward.  The trough will also bring another surge of colder mid-level temperatures, further destabilizing the air mass. At the same time, there is an increase in low-level moisture. This moisture can be tracked back to an area east of 150°W, where there is currently an area of showery cumulus clouds. Forecast soundings show the weak inversion dissipating with the approach of the upper trough. With the destabilizing air mass and increase in moisture, there is the possibility for thunderstorms again. The potential is centered around Tuesday night, but could begin earlier or linger into Wednesday morning. The trend has been toward more destabilization across the entire state, so we will expand the slight chance of thunderstorms to encompass all islands. However, this is an uncertain situation without a well-defined trigger to initiate convection, and further adjustments will be necessary.

Looking further into the second half of the week, weather models show the upper low shifting westward, eventually starting to weaken by the weekend. Forecast soundings show some mid-level drying and weak stabilization, but not to the degree that we see currently. We remain in a wet pattern through the week. The GFS and ECMWF models both show a surge in moisture centered around Friday, associated with the remains of a dissipated front.

At the surface, winds will remain fresh to strong through the week. High pressure far to the east-northeast of the state will give way to a stronger high building in far north of the state by mid-week. This high will lead to a strong pressure gradient over the islands. Winds are expected to increase on Wednesday and remain strong through the week, eventually starting to weaken over the weekend.

Marine Forcast: A Small Craft Advisory remains in effect for the typically windier waters near Maui County and the Big Island. This area will likely be expanded to cover all the coastal waters by midweek for a combination of fresh to strong trades as well as increasing combined seas. A High Surf Advisory may also be needed along east facing shores for rough and choppy surf late in the week.

The following numbers represent the strongest wind gusts (mph), along with directions Monday morning:

23                 Port Allen, Kauai – ENE
30                 Bellows AFB, Oahu – E
24                 Molokai – NE
37                 Kahoolawe – E
31                 Kahului Apt, Maui- ENE
0                   Lanai 
40                Bradshaw FLD/Hawaii (BSF), Big Island – ESE

Here are the 24-hour precipitation totals (inches) for each of the islands as of Monday morning:

1.36               Mt. Waialeale, Kauai
0.16              Kahuku, Oahu
0.00              Molokai
0.00              Lanai
0.00              Kahoolawe
0.02               Puu Kukui, Maui
0.72              Kealakekua, Big Island

Here is the latest NWS rainfall forecast

Here are the latest available satellite images:

Hawaii Infrared satellite image 
Animated Satellite image of Hawaii region
Latest satellite image – Close-in visible satellite view
Latest radar image – Looping

SURF ZONE FORECAST – OAHU
NATIONAL WEATHER SERVICE HONOLULU HI
900 AM HST MON NOV 7, 2011

Surf along north facing shores will be 3 to 6 feet today then drop to 1 to 3 feet Tuesday.

Surf along south facing shores will be 3 to 6 feet through Tuesday. 

Surf along west facing shores will be 1 to 3 feet then drop to flat to occasional 2 feet Tuesday.

Surf along east facing shores will be 1 to 3 feet today then drop to flat to occasional 2 feet Tuesday.

Outlook through Sunday Nov 13:  The current northwest swell will fade into tomorrow. More overhead northeasterly swell is expected during the second half of the week. Trades will maintain head high short period chop along windward reefs and beaches over the next several days. Surf along south facing shores will go flat and stay below average for quite some time.

NOAA animated wave model