Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
197 FXHW60 PHFO 161937 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 937 AM HST Tue Jul 16 2024 .SYNOPSIS... Breezy trade winds today will ease to moderate strength 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... Some slight adjustments to shower chances and sky cover have been made to the forecast for the rest of today based on the latest guidance and observations with this morning`s updates. Broad high pressure remains between 30N and 35N, which continues to steer locally breezy trade winds across the islands. An upper level ridge over the state is helping to maintain a very stable and relatively dry airmass. Latest satellite and radar imagery shows stable clouds moving into windward sections of the islands, particularly from Kauai to Oahu, with fewer clouds embedded within the trades upstream of Maui County and the Big Island. Any showers that are occurring are light and favoring windward and mauka areas. 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 the day due to strong trades. && .MARINE... A broad surface high over the central and eastern Pacific will maintain fresh to locally strong trade winds through tonight. The Small Craft Advisory (SCA) remains in effect for the typical windier waters around Maui County and the Big Island. Winds may fall below the SCA threshold by Wednesday morning as low pressure northeast of the islands causes winds to weaken. Existing long period S swell is still holding in the 16 second range per the latest nearshore and offshore buoy data. The High Surf Advisory (HSA) remains in effect through today and will be reevaluated prior to expiration this afternoon. This swell will slowly decline through Thursday and then drop to background levels Friday into the weekend. Surf remains choppy along east facing shores but can be expected to slowly subside as upstream trades weaken. In addition, a small pulse out of the NE quadrant has arrived at the nearshore buoys and will continue filling in today providing a tiny boost to north and east facing exposures. North facing shores may see a tiny bump from the combination of a small, medium period northwest swell and the northeast swell mentioned above today into Wednesday but will quickly fade Wednesday night. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until 6 PM HST this evening for Niihau-Kauai Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-Kona-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central Valley South-South Maui/Upcountry-South Haleakala-Big Island South-Big Island Southeast. 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