Light to moderate trade winds this morning will gradually strengthen over the next few days with moderate trades expected over the weekend. Brief passing showers will drift into the islands on the northeasterly trade winds, favoring windward and mountain areas during the overnight to early morning hours. A more significant change to our weather pattern continues to evolve for early next week beginning sometime Monday night or Tuesday. Deeply unstable tropical moisture moving across the state will bring the potential for heavy rain and thunderstorms affecting all islands through at least the middle of next week.
The trade winds have eased to become light to moderate in response to the weakening pressure gradient as the surface high gets pushed farther northeast of the state and a low pressure system sets up to the north. As this low continues to drift southeastward, high pressure will build behind and will allow the northeasterly trades to gradually strengthen through the weekend. Moderate trades are expected later this afternoon and could become locally breezy in a few areas this weekend as the remnants of a dissipating frontal boundary moves into Kauai on Saturday and over Oahu on Sunday. An increase of trade wind showers should be expected as the old frontal boundary moves through this weekend.
Also a weak trough southeast of the Big Island could bring an uptick of moisture over windward Big Island this weekend. Brief downpours will be possible, especially over the windward slopes during the afternoons.
Starting next week, a very unusual weather pattern is expected to develop over the state. A surface low is expected to develop near 15N and the international dateline this weekend. This low pressure system will gradually track eastward next week. While tracking eastward, a deep upper level trough will develop just west of the state and will transport a broad area of deep tropical moisture (with precipitable water values of up to 2.5 inches) over the state around Tuesday and Wednesday of next week. While there are still some timing differences, there is potential for significant heavy rain and flash flooding towards the middle of next week. Due to the broad band of deep moisture, it is going to be difficult to pinpoint what areas will be impacted the most and will highly depend on where the clusters of thunderstorms develop. While, heavy rain and flash flooding will be the main concern, some damaging winds will be possible with any thunderstorms.
Gentle to moderate trade wind weather is expected today with mostly VFR conditions. An increase of showers around PHTO could produce brief MVFR conditions later this afternoon.
A strong jet developing today with the jet streak located just north of the state could produce light to moderate turbulence around Kauai and Oahu between FL240 to FL320. Severe turbulence will be possible further north of the state especially this afternoon into Saturday morning. See SIGMET ROMEO for more information.
No AIRMET's are in effect, but we may need AIRMET TANGO later today if we begin to see reports of moderate turbulence.
Easterly trade winds will be at gentle to moderate strength through Friday as surface low pressure far north of Hawaii and a nearby surface trough weaken the local pressure gradient. Trades are expected to hold at current strength and shift out of the northeast this weekend as high pressure far northwest of Hawaii pushes the low eastward. The weaker trade winds should persist Monday, but uncertainty increases on Tuesday, hinging on the potential development of a low southwest of the islands.
A small, medium-period northwest swell will arrive overnight and provide a small boost to surf along north-facing shores on Friday. A moderate, medium-period north-northwest swell will build late Saturday and peak around seasonal average on Sunday. As this swell declines on Monday, a long-period west-northwest swell will arrive, maintaining small to moderate surf into the middle of next week.
Small background level surf will prevail along south-facing shores through Friday. A small to moderate south-southwest swell is expected to boost surf to around seasonal average this weekend into early next week.
Along east-facing shores, trade-wind swell will continue to decrease through Friday, though a small, medium-period northeast swell may maintain small surf through Saturday. Aside from wrapping north-northwest swell in exposed areas, east shore surf should remain below seasonal average much of next week.
None.
