Hawaii Weather Synopsis: A weak front well to the northwest of the Hawaiian islands will keep winds light today with afternoon sea breezes and some interior and leeward showers. A ridge building north of the islands will return light to moderate trades Thursday through Saturday, along with a few more showers for windward and mauka sections. Another front approaching from the northwest will bring a prolonged period of light winds to the State for much 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 19 Oct 2011 at 10:05am HST
A weak stationary front about 500 mi NW of Kauai is keeping a weak pressure gradient over the main Hawaiian islands today (see latest weather map). This will lead to another day of afternoon clouds and scattered mainly interior showers. Given the weak easterly background flow, after they develop, these will tend to drift west with time toward leeward shores. The forecast grids and text products were adjusted earlier to better match NWS expectations. The 12Z soundings showed the inversion heights and boundary layer moisture are similar to yesterday, so while a brief downpour or two in the heaviest cells cannot be ruled out, flooding rains are not anticipated.
Guidance is in good agreement that the subtropical ridge to the north will temporarily reestablish itself to the N starting this evening and continuing through about Saturday. After Saturday, the ridge starts to consolidate into a high that will move away to the NE, and the pressure gradient weakens once again over the State as yet another autumn front approaches from the NW. A prolonged period of light winds with daytime sea breezes and nighttime land breezes, along with higher humidity that will last well into next week is expected. Forecast adjustments are in progress for this time period. Models show the airmass over the islands will be more moist and mid levels will be somewhat cooler by the middle of next week, so afternoon convective showers will probably be a little more vigorous by then.
In the marine environment, winds could approach Small Craft Advisory criteria around the normally windier areas such as South Point on the Big Island and through the Alenuihaha channel on Thursday or Friday, but for now winds remain below Small Craft Advisory levels.
A series of weak lows over the north Pacific over the past few days will send a short-period bump in NW swell, arriving Wed night and lasting through Thursday. A stronger low developing near the Aleutians Thursday/Friday will send a more significant swell that should arrive on Sunday. The current south swell, generated south of Tahiti several days ago, will continue to diminish. Low pressure near New Zealand could send a small SW bump toward the State of Hawaii for Monday but the probability looks rather low at this point.
The following numbers represent the strongest wind gusts (mph), along with directions Wednesday morning:
08 Princeville, Kauai – ESE, and Lihue, Kauai – ENE
23 Kaneohe, Oahu
09 Molokai – ENE
22 Kahoolawe – ESE
16 Kapalua, Maui – E
06 Lanai – ESE
24 Upolu Airport, Big Island – ENE
Here are the 24-hour precipitation totals (inches) for each of the islands as of late Tuesday night:
0.42 Puu Opae, Kauai
1.13 Punaluu Pump, Oahu
0.05 Kaupo Gap, Maui
0.11 Pahala, 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 WED OCT 19 2011
Surf along east facing shores will be 4 to 6 feet today, lowering to 2 to 4 feet Thursday.
Surf along north facing shores will be 2 to 4 feet through Thursday.
Surf along south facing shores will be 3 to 4 feet through Thursday. Locally higher sets today.
Surf along west facing shores will be 1 to 3 feet through Thursday.
Outlook through Tuesday Oct 25: A new northwest swell will build this weekend, with surf peaking near the advisory level of 15 feet along north facing shores for Sunday and Monday. The current south swell will slowly diminish through the week, and will be followed by another small south-southwest swell on Monday.