Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
634 FXHW60 PHFO 261946 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 946 AM HST Sun May 26 2024 .SYNOPSIS... Broad high pressure north and northeast of the state will maintain moderate to locally breezy easterly trade winds through the week. Showers will mainly favor windward and mauka areas, with areas of high clouds passing overhead at times. && .DISCUSSION... At the surface, broad high pressure far north of the islands is driving moderate to locally breezy trade winds across the state. Meanwhile, satellite imagery shows showers and thunderstorms with a surface trough and its attendant low aloft roughly 600 nm west of Kauai. This is causing the trades to veer slightly more east- southeast than usual, particularly across the western islands. Showers favoring windward locations have remained fairly light this morning, though some areas of Kauai did receive meaningful rainfall overnight. Little change is expected over the next few days as high pressure gradually strengthens north/northwest of the islands and the trough and upper low west of the state remains nearly stationary through Tuesday. Shallow moisture embedded within the trades will produce some windward and mauka showers at times, particularly during the overnight through early morning hours each day. Additionally, expect spotty afternoon and evening showers, some briefly heavy, across leeward portions of the Big Island. The trough`s proximity to the western end of the state will weaken the inversion at times near Kauai and could enhance shower activity there, similar to last night. However, guidance is in agreement that the trough will remain far enough west of the main Hawaiian Islands to have little impact to local weather otherwise. The surface high will settle far northeast of the state and hold into Friday, while the surface trough lingers west of the islands and produces breezy easterly trade winds. The nearby upper-level trough will weaken around mid-week, leading to greater stability and supporting a more typical trade shower pattern favoring windward and mauka areas. && .AVIATION... A fairly stable pattern will remain over the state over the next few days with some passing high clouds overhead. Moisture embedded within the trade flow will allow for SHRA over windward and mauka areas. VFR conds should prevail over most locations, with MVFR conds possible in any SHRA. AIRMET Sierra is in effect for mtn obsc for, windward Big Island and NE through SE portions of Kauai. Conditions are expected to improve later this morning, but conditions could return tonight especially over windward Big Island. AIRMET Tango remains in effect for moderate low-level turb downwind of island terrain. This AIRMET will likely remain in effect through much of this week. A weak shortwave trough passing just west of the state on Monday should bring an increase of mid level clouds around Kauai Monday afternoon and evening. Although low probability, there is a chance for some light icing between 160 and FL250 Monday afternoon through Monday night. && .MARINE... Moderate to strong easterly trades will continue through the week as the surface ridge remains positioned north of the state. The strongest winds are expected over the windier waters around Maui County and the Big Island, supporting the Small Craft Advisory. The lightest winds are anticipated over the Kauai waters, fluctuating between east and east-southeast over the next few days due to a persistent surface trough to the west. Surf along exposed south-facing shores will remain small throughout much of the week, mainly due to a combination of background south-southwest and southeast swell energy. An upward trend is expected from Friday through the first week of June due to an active pattern unfolding within our swell window near New Zealand. Altimeter and ASCAT passes over the past 24 hours reflected the potential for next weekend, showing a broad swath of gales with seas up to 30 feet focused at the state within the 190-200 degree directional bands. This will mark the beginning of a long-lived event with additional reinforcements expected within the same area over the next several days. Surf along exposed east-facing shores will remain small and choppy throughout the week as the trades persist. Surf along exposed north-facing shores may increase slightly later today through Monday due to a small, medium-period northwest swell expected. Otherwise, summertime conditions are anticipated with minimal surf expected this week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Monday for Pailolo Channel- Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Vaughan AVIATION...Kino MARINE...JVC