Hawaii Weather Synopsis: A high far northeast of the area will produce gentle to moderate trade winds through tomorrow. The trades will produce windward showers that will be most frequent during nights and mornings. A trough developing west of Kauai will disrupt the trade winds starting Sunday. The weather will turn muggy and hazy with clouds and showers during the afternoons and evenings. Unsettled weather will continue most of next week.
No Advisories, Watches, or Warnings are currently in effect.
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Broad Overview of Hawaii’s Weather
Based on the NWS Area Forecast Discussion for Hawaii, issued 21 Oct 2011 at 10:00am HST
Surface analyses show a 1027 mb surface high about 1600 miles northeast of the main Hawaiian Islands with a ridge extending west to a point about 600 miles north of Kauai (see latest weather map). The ridge north of the islands will produce gentle to moderate trade winds. Satellite imagery shows scattered to broken low clouds east of the islands. The trades will push these clouds across the islands producing showers over mainly windward areas. No heavy rainfall is expected from these trade-wind showers. There is a low aloft about 550 miles west northwest of Kauai. There is a north-south surface trough beneath the low. Southwest winds aloft associated with the low are carrying high, cirrus clouds over the main Hawaiian Islands. These clouds will not produce any precipitation.
The global forecast models are in good agreement showing the surface trough west of Kauai deepening over the next few days. The models show a surface low forming within the trough by Saturday evening, then show a front developing and moving southeast toward the main Hawaiian Islands. As the trough deepens the winds over the main Hawaiian islands will weaken and veer out of the southeast. As the low level flow veers, the Big Island will partly block the flow and winds will become weak from Maui to Kauai while moderate trades will persist near the Big Island. Toward the end of the week the winds may become light near the Big Island too.
With the low level flow weakening and shifting to southeast the weather pattern over the islands will shift from night and morning showers over windward areas to afternoon clouds and showers over interior areas. The atmosphere will be stable enough to limit rainfall early in the week. Later in the week, moisture and instability will increase and showers may become heavier. The models become less consistent later in the week so it is too early to be very confident about the forecast during that period.
In the marine environment, low pressure over the Aleutians is generating the next NW swell now. There is excellent model agreement to support the Wavewatch III timing and height of the next northwest swell, still scheduled to arrive Saturday night. NWS still expects surf along north and west facing shores will peak near the 15 foot advisory level on Sunday.
The following numbers represent the strongest wind gusts (mph), along with directions Friday morning:
13 Princeville, Kauai – ESE
17 Bellows AFB, Oahu – ENE and Kaneohe, Oahu – ESE
14 Molokai – E
25 Kahoolawe – E
20 Kapalua, Maui – ENE
25 South Point, Big Island – E
Here are the 24-hour precipitation totals (inches) for each of the islands as of Friday morning:
0.84 Mt. Waialeale, Kauai
0.51 Nuuanu Upper, Oahu
0.26 Puu Kukui, Maui
0.11 Kealakomo, Big Island
Here is the latest NWS rainfall forecast
Here are the latest available satellite images:
SURF ZONE FORECAST – OAHU
NATIONAL WEATHER SERVICE HONOLULU HI
900 AM HST FRI OCT 21 2011
Surf along north facing shores will be 1 to 3 feet through Saturday.
Surf along east facing shores will be 1 to 3 feet through Saturday.
Surf along south facing shores will be 1 to 3 feet through Saturday.
Surf along west facing shores will be 2 feet or less through Saturday.
Outlook through Thursday Oct 27: A northwest swell will build this weekend with surf peaking near the advisory level of 15 feet along north facing shores Sunday and Monday, then gradually diminishing through mid week.