Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
442 FXHW60 PHFO 170141 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 341 PM HST Tue Jul 16 2024 .SYNOPSIS... Breezy trade winds will ease to moderate levels Wednesday through Friday as broad high pressure north of the state weakens. Stable and fairly dry conditions will prevail throughout much of the week, with light showers favoring windward and mauka areas. This weekend, a trough could increase windward showers, particularly across the eastern end of the state. && .DISCUSSION... Broad high pressure north of the state is steering locally breezy trade winds across the islands this afternoon. Meanwhile, an upper level ridge is helping to maintain a very stable and relatively dry airmass. Latest satellite imagery shows some scattered clouds embedded within the trades moving into windward and mauka locations, though even these are rather sparse across the eastern end of the state with little notable moisture upstream. Rainfall has been rather sparse today as well, mostly confined to a couple of afternoon sea breeze-induced showers along the leeward section of the Big Island. Otherwise, any showers that are occurring are light and favoring windward and mauka areas. A few tweaks have been made to the forecast throughout the next week to trend towards the latest guidance, but the overall forecast philosophy remains unchanged. The ridge to the north is expected to weaken, which will allow trades to ease some tonight and Wednesday. Stable conditions will persist with limited moisture in the trade wind flow. As a result, expect modest windward rainfall. Aside from a few afternoon showers on Kona slopes of the Big Island, leeward areas should remain dry. In the long range, trades may strengthen during the weekend. The GFS and ECMWF suggest that a trough in the vicinity of the islands could increase trade wind showers this weekend, particularly across the eastern half of the state. && .AVIATION... Breezy trade winds will continue through tonight, then gradually ease through the end of the week. Light showers and limited low clouds will favor windward and mauka areas and could bring brief periods of MVFR. Otherwise, VFR will prevail. AIRMET Tango for moderate low-level turbulence lee of island terrain remains in effect and will continue through tonight due to strong trades. && .MARINE... Fresh to locally strong trades will weaken to moderate late tonight into Wednesday as weak troughing develops northeast of the islands. The Small Craft Advisory for the typical windier waters of Maui County and the Big Island remains posted through tonight. Existing long period S swell is slowly subsiding, the bulk of energy now shifting toward the 13 to 15 second bands per the latest buoy observations. The High Surf Advisory (HSA) is no longer in effect, though surf will still approach the HSA threshold in favored areas at times, particularly during the first half of tonight. This swell will then slowly decline during the latter half of the week, dropping to background levels Friday into the weekend. Surf remains choppy along east facing shores due to trades and is also experiencing a very modest bump from a small NE swell. North facing exposures may see a tiny bump from the combination of a small, medium period northwest swell and the small northeast swell mentioned above tonight into Wednesday but will quickly fade Wednesday night. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Vaughan AVIATION...Ahue MARINE...JVC