Strong high pressure far north of the state will continue to produce breezy trades into the weekend. One batch of trade wind showers will spread across mainly Maui and the Big Island tonight with a quick downpour or two possible windward. Another increase in moisture will bring enhanced showers to mostly windward and mauka locations Saturday night into Sunday. Otherwise fairly typical trade wind weather is expected.
Very large surface high 1035 mb or so meanders over the far NE Pac the next 10 days, keeping trades breezy with slight slackening expected by the middle of next week. One bactch of enhanced showers is rolling into Maui and the BI, associated with higher PW around 1.75" moving in, enough for a couple of quick windward and mauka downpours. Oahu should be on N fringes of this moisture convergence later tonight and Fri AM. Still another shower area progged near the islands in the ensemble means Sat night into Sun AM. Ridging persists aloft, so nothing too unusual expected with either of these. Otherwise, typical windward and mauka showers expected with PW trending near normal thru midweek next week.
However, the latest ensemble runs and current MJO phase suggest we keep an close eye on the tropics to our S and SE the over the next couple of weeks. There is more agreement in the long range than I'd like to see, that the ITCZ to the S and SE of the islands will become even more active. The subtropical jet shifts N of the islands in a week or so, anticyclonic flow builds aloft SE of the islands, and deeper tropical moisture and much- below- normal surface pressure gradually get established to our S and shift northward. Just a little tap on the shoulder to remind us that while it is quiet over the islands for the time being, we are getting farther into Hurricane Season with what is expected to be a very strong El Nino continuing to build.
Moderate to breezy trades will persist across the Hawaiian Islands, bringing in pockets of enhanced low-level showers across predominately windward and mauka areas. Expect VFR conditions to prevail across most locations, with occasional localized MVFR conditions in association with shower activity.
AIRMET Sierra is in effect for mountain obscuration above 2500 feet for windward Kauai, Oahu, Maui, and the Big Island. This is expected to persist throughout the period as shower activity continues, even if showers prove to be intermittent at times.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of terrain for all islands. This AIRMET will likely continue through the next several days.
Strong high pressure centered north of the state will remain nearly stationary over the forecast period driving fresh to strong trade winds across the entire coastal waters. The Small Craft Advisory (SCA) is in effect through Friday afternoon for all Hawaiian waters. Trades will remain fresh to strong through the weekend so the SCA may need to be extended but a few leeward zones might drop off.
The current small medium-period south-southwest (190-200 degrees) swell will gradually decline through Friday. A small to moderate, long- period southwest swell (220 degrees) is expected to fill in Saturday into early next week, but due to its Tasman source, could be more inconsistent than the current swell.
Surf along east-facing shores will remain rough and choppy through the forecast period as fresh to strong trades hold. A series of small, moderate- to long-period west (270 to 280 degrees) swells are expected to arrive late Friday and hold into early next week, sourced from Typhoon Bavi in the far western Pacific. Surf along north-facing shores is expected to remain flat to tiny with no significant swells forecast from the north or northwest.
Looking ahead, higher than normal high tides will be possible beginning during the latter half of this weekend. Interests immediately along the coasts in low-lying or vulnerable areas should continue to monitor forecasts for possible coastal flooding due to the King Tides from Sunday through the first half of next week.
Small Craft Advisory until 6 PM HST Friday for all Hawaiian waters-
