Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
921 FXHW60 PHFO 270645 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 845 PM HST Sun May 26 2024 .SYNOPSIS... 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 passing areas of high clouds at times. && .DISCUSSION... Broad high pressure far north of the islands continues to drive moderate to locally breezy trade winds across the state. Infrared satellite imagery shows an area of showers and thunderstorms roughly 550 nm west of Kauai associated with a surface trough and its attendant low aloft. This feature is also causing local trades to veer slightly more east-southeasterly than usual, particularly across the western islands. Afternoon soundings from Lihue and Hilo show mostly stable conditions with temperature inversions around 6000 and 7000 ft, respectively. The latest radar imagery shows only a few light showers scattered around the state. Little change is expected in the overall pattern through Tuesday, as high pressure gradually strengthens to the north/northwest and the surface trough and upper low west of the state remain nearly stationary. 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 on local weather otherwise. For the rest of the week, 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. 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 for mtn obsc could return tonight across windward areas especially over Big Island as a plume of moisture moves in late tonight. 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. With a weak shortwave trough passing just west of the state on Monday and increased mid level clouds around Kauai the potential exists for AIRMET Zulu to be needed for 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, 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 couple of days reflected the potential for next weekend, showing a broad swath of gale- to storm-force winds 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. For north-facing exposures, expect summertime conditions with minimal surf 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...TS AVIATION...SMW MARINE...Gibbs