Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
922 FXHW60 PHFO 160114 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 314 PM HST Tue Jul 15 2025 .SYNOPSIS... A high pressure system will remain far northeast of the state through the week before shifting westward over the weekend into early next week. Moderate to locally breezy trade winds will persist through the forecast period. Stable conditions will build over the state with best chances of rainfall along windward and mauka areas, especially during the overnight hours. There may be a slight increase in shower activity as early as Thursday night into the weekend as a upper level disturbance moves over the islands. && .DISCUSSION... A surface high pressure roughly 1750 miles northeast of the state is generating moderate to locally breezy trade winds. Satellite and radar imagery shows clouds and showers focusing along windward and mauka areas. The past 3 hour rainfall totals range from .01 to .33 inches with the highest totals generally over the wetter areas of Kauai where a slightly enhance moisture plume continues to exit westward. There are also some clouds and showers building over and along the kona slopes of the Big Island this afternoon as sea breezes developed. As the evening progresses expect clouds and showers to diminish along the kona slopes and to increase over the windward and mauka areas. This typical diurnal tradewind pattern is expected to repeat each day through the forecast period as the high pressure system remains anchored far northeast of the state. As early as late Thursday into the weekend windward clouds and shower activity may see a slight uptick as an upper level low develops northwest of Kauai and low level moisture is advected in. In addition, a few showers may move over to leeward areas at time along the smaller islands as inversion heights increase, especially during the overnight and early morning hours. Confidence in these shower trends remain moderate at this time, as the strength of the upper low is currently projected to be on the weaker side of the equation. More details will become clearer later this week, as the time period grows closer, and our confidence on island by island shower trends improve. && .AVIATION... Locally breezy trade winds will persist through much of the week as high pressure holds far north of Hawaii, and stable conditions will prevail during the next several days. Periods of MVFR ceilings and visibility are expected over windward slopes, where AIRMET Sierra for mountain obscuration may be needed during some overnight and morning hours. VFR will dominate across leeward areas. Under the breezy and stable trade wind flow, some low level turbulence is expected over and downwind of terrain, and some strengthening of low level winds in the guidance suggests that AIRMET Tango will be needed on Wednesday. && .MARINE... High pressure will remain far northeast of the state throughout the week. Fresh to locally strong trades will likely persist through most of the week, although we could see wind speeds drop slightly as a weak trough develops near the western end of the state into the weekend. A Small Craft Advisory (SCA) is now in effect for the typical windy areas around Maui County and the Big Island through Wednesday night. A long-period south swell caused surf along south facing shores to peak near the summer average earlier today. As this swell declines, a reinforcing short-period south-southeast swell will continue to fill in this evening into Wednesday, slowing the decline of surf heights through Friday. Another small increase is expected heading into the weekend as a new long-period southwest swell arrives from the Tasman Sea. Surf along east facing shores will continue to remain rough and choppy with a slight boost in surf heights expected through mid week as the trades strengthen and again late this week into the weekend as a short-period northeast swell fills in. Surf along north facing shores will continue to decline through Wednesday and remain nearly flat through the weekend. && .FIRE WEATHER... Trade winds will remain in the moderate to locally breezy range through the forecast period. Weather conditions will become more dry and stable over the next couple of days. Shower trends may increase as early as Thursday night into the weekend as an upper level disturbance moves over the island chain and low level moisture increases. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Almanza AVIATION...Wroe MARINE...Farris/Vaughan FIRE WEATHER...Almanza