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Dec
08
2011

Hawaii Weather Overview

Gradually strengthening trade winds,  windward biased showers for the most part…still large surf along our north and west facing beaches into Friday.

PDC Global Hazards Atlas centered on the central Pacific Ocean near Hawaii is displaying 3 hour precipitation accumulations over the last three hours

Hawaiian Weather Synopsis:  The trade winds remain well established across our Hawaiian Islands today, with little change expected through the next week…other than a possible strengthening after this weekend. The main instigator here is a very steady and strong near 1037 millibar high pressure system, which seems to be cemented into place far northeast of us. This high pressure cell is in control of weather conditions from Alaska and the eastern half of the Gulf of Alaska, all the way down the west coast past BC Canada, Washington, Oregon, and the California coast into Baja, California…even down to the Central American coast!

This high pressure system is flooding air from the far north, down south into the tropics. This high, or a new one with time, will keep up this conveyor belt of air coming over us well into the future. This is turning out to be, or will turn out to be in the end, an especially long lasting bout of late autumn trade winds. They are strong enough now to have overlapped almost the entire state with small craft wind advisories. We certainly haven’t seen the last of this advisory, which will be in force through the next week at least. These likely won’t become strong enough to cause trouble for our islands, although will make the east sides of the islands wavy, and cause rough choppy ocean conditions too…not to mention carry lots of showers our way.

In terms of rainfall, we’ll find the usual passing windward showers, how many times have you read that…about a million? At any rate, they will be falling in an off and on fashion through Friday. As we push into the weekend, there’s still that chance of an increase in showers, although there are several variables that could come into play here. They could be more of  those very common showers that the trade winds drag in, or they could become more numerous than usual, and even quite generous in their intensities. This has been an ongoing question in the weather forecasting community all this week, and still isn’t perfectly clear. It will be determined, in an easy way of stating the problem, by whether we get cold air aloft over the state, how cold it turns out to be, and, whether there is enough moisture around to feed these potentially frequent passing showers along our windward sides. This by the way could extend right on into the new week ahead, and could bring some much needed showers over into the leeward sides, especially on the smaller islands.

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

Details of Hawaii’s Weather – Wind/Precipitation/Surf

As this weather map shows, we find a strong 1037 millibar high pressure system located far to the northeast of the Hawaiian Islands Thursday afternoon.  This high pressure cell remains nearly stationary well offshore from the Columbia River mouth, between the Oregon and Washington borders.  This high has a ridge of high pressure running from its center southwest into the area north-northeast of Hawaii. Meanwhile, we see a weaker 1025 millibar high closer, to the north of the islands.  Finally, we have troughs of low pressure located to the east and north of the state. The long and short of all this keeps moderately strong trade winds blowing across our latitudes of the north central Pacific…strongest over the Maui and Big Island end of the chain.

The following numbers represent the strongest wind gusts (mph), along with directions early Thursday afternoon:

25                 Port Allen, Kauai – NE
25                 Kahuku Training, Oahu – NE
25                 Molokai – NE
33                 Kahoolawe – E
32                 Kahului, Maui – NE
35                 Lanai – NE
37                 Puu Mali, Big Island – NE

We can use the following links to see what’s going on in our area of the north central Pacific Ocean early Thursday afternoon. Looking at this NOAA satellite picture we find that high and middle level cloudiness are located over the ocean to the east and southeast, along with fairly minor low clouds stretched across the windward sides, most concentrated on the Big Island and Kauai. We can use this looping satellite image to see low clouds being carried over the islands on the trade wind flow here and there…although skies were quite clear in some areas today.  We can see a large area of thunderstorms over the ocean to the southeast of the Big Island, with high cirrus clouds flying off the tops of those storms…carried by the strong upper level winds in that area. Checking out this looping radar image we see showers over the ocean, most of which are in the light to moderately heavy category. The most active precipitation areas are coming into the  windward sides..especially on Oahu, Maui, and to the southeast of the Big Island. 

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

0.83               Mount Waialeale, Kauai
0.38               Manoa Lyon Arboretum, Oahu
0.06               Molokai
0.00               Lanai
0.00               Kahoolawe
1.35               Puu Kukui, Maui
0.75               Pahoa, 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 OUTLOOK:   Surf along the east shores will remain active, rough and choppy Thursday and Friday…generally on the small side or a little larger. The north shores will be rising significantly Thursday into Friday. The west sides will be coming back up again Thursday into Friday as well. South shores will be small Thursday and Friday.

North shores –  A new large northwest swell will arrive early Thursday, remaining active for several days…gradually lowering through the weekend. The largest surf Thursday in those best aligned spots will be 8-12 feet.

West shores –  The new large northwest swell will bring these beaches up Thursday into Friday, gradually lowering Saturday and Sunday. The largest surf Thursday in those best aligned spots will be 6-8+ feet.

South shores –   Surf will remain small on these leeward shores

East shores –  Surf will gradually rise…as the strengthening trade winds bring choppy and rough conditions into the weekend and beyond.

NOAA animated wave model