Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
953 FXHW60 PHFO 181906 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 906 AM HST Sat Jul 18 2026 .SYNOPSIS... Locally breezy trade winds will remain through the weekend, easing a bit early next week. A trend toward fewer windward and mauka showers, and more sunshine, is expected this weekend as drier air pushes in on the trades. Typical trade wind showers will return early next week. && .SHORT TERM UPDATE... Skies were partly to mostly cloudy in most areas this morning, with isolated showers in windward and mauka locations. Trades were averaging 10 to 20 mph sustained, with gusts 20 to 30 mph in the typical windier locations. Today will be a fairly normal summer trade wind day, and the current forecast describes the situation well. No update is planned at this time. && .PREV DISCUSSION... Issued at 310 AM HST Sat Jul 18 2026 A persistent, large 1033 mb surface high over the far NE Pacific has been keeping locally breezy trades blowing across the Aloha State for quite a long while now. An area of moisture, and perhaps a very weak surface trough, riding through on the trades has been enhancing windward and mauka showers overnight, especially for Big Island and Maui. A few windward Big Island gauges have picked up 1.5 to 2 inches of rain in the last 12 hours although more recently, those showers have been diminishing. The area of moisture will move west of us during the day today for a decrease in trade wind showers and increasing sunshine. Models are in good agreement that a pocket of drier air will overspread the state tonight into Sunday, especially for the smaller islands, and this should lead to fewer windward and mauka showers. A modest increase in moisture returns by Tuesday for a few more showers once again, and then the multi-model ensemble means show the airmass drying out again for the second half of the week. Models agree the pressure gradient will tighten just a bit leading to a minor uptick in tradewind speeds today. This uptick will be short-lived as a weak front far to our N temporarily disrupts the NE Pac high Sunday into Monday. Starting Tuesday, the NE Pac surface high reestablishes and strengthens, leading to a slow, gradual increase in trade wind speeds. It will take a few days, but should be breezy to locally windy by Friday as the high peaks in intensity around 1037 mb far N of us. We will keep an eye on the developing tropical disturbance several hundred miles SW of Ixtapa, Mexico. Various ensemble systems have been showing a small potential for this system to bring us some tropical trouble in about a week and a half or so. Much too early to speculate on any details, and plenty of ensemble members don`t bother us with it at all. However, a good reminder to stay prepared. && .AVIATION... Moderate trades will continue through Sunday, with just a slight decrease in speed tomorrow. Clouds and showers will be focused over windward and mauka locations. Conditions will be VFR apart from isolated MVFR over windward and mauka areas in clouds and showers. No AIRMETs in effect. There is the possibility of an AIRMET for mountain obscuration during the afternoon and evening hours. && .MARINE... High pressure far northeast of the islands and a passing broad trough to the south will maintain fresh to locally strong trades across the region through at least this afternoon. The Small Craft Advisory (SCA) currently in effect through 6 PM HST this evening has been expanded to include most waters surrounding The Big Island and Maui County, including the windward zones and Kaiwi Channel. Winds will begin to decrease Sunday into early next week as high pressure to the north starts to weaken, which should scale back and then eliminate the need for a SCA. Then as high pressure builds back to the north, trades will strengthen over the latter half of next week. Surf along south facing shores will remain elevated keeping levels near average through the day today. A larger, moderate south swell is expected to build Sunday through early next week, bringing potentially High Surf Advisory level conditions Monday and Tuesday. As this swell slowly fades into the middle of next week, another moderate south-southwest swell is expected to arrive next Thursday. A small, medium-period west-northwest swell will gradually fade through the weekend, causing surf along north-facing shores to drop to flat/tiny levels. East facing shores will remain choppy today and then will gradually drop through the rest of the weekend into early next week as trade winds ease. Energy from Tropical Storm Elida may reach the islands during the middle of next week and bring a slight boost for east facing shores. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Maalaea Bay-Maui County Windward Waters-Pailolo Channel. && $$ SHORT TERM UPDATE...Parker DISCUSSION...R Ballard AVIATION...Parker MARINE...Tsamous