Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
702 FXHW60 PHFO 021935 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 935 AM HST Sun Jun 2 2024 .SYNOPSIS... Breezy trades will continue into the middle of the week before weakening and giving way to land and sea breezes during the second half of the week. An upper level trough over the islands through Tuesday may bring some heavier showers at times, especially over interior Big Island where there will be also be a chance for afternoon thunderstorms. && .DISCUSSION... At press time the Hawaiian Islands are enveloped within the cyclonic flow pattern around a mid-level low positioned a couple hundred miles northeast of the area. Occasional shortwaves embedded in the circulation around this low are rotating through the area, but there is no sign that these waves of forcing are having a meaningful effect at the surface, a testament to existing low-level stability. Little change is therefore expected during the next 24-48 hours for most of the area as the low pivots over the area and its -10 to -12C cold pool becomes established overhead. Relatively stable and breezy trades will therefore continue for the smaller islands into mid- week. Conversely, this elevated unstable layer will be easily accessible during diurnal heating over the interior slopes of the Big Island Monday and Tuesday afternoons. The official forecast handles this potential well with a mention of isolated thunderstorms each day. The leeward island plumes over the nearshore waters are also potential candidates for isolated thunderstorms Monday and Tuesday nights, but confidence remains too low to include in the forecast at this time. The second half of the week will feature a developing mid-level ridge centered along 30N well west of the islands which, in tandem with the occasional mid-latitude trough encroaching on the forecast area, will cause the trade wind belt to contract and migrate south of the islands Thursday into the weekend. This in turn favors warmer conditions and potential for an emerging land and sea breeze pattern. && .AVIATION... Breezy to strong trades will continue, as a surface high moves closer to the state from the northeast. Low clouds and showers will favor windward and mauka areas with periods of MVFR conditions possible. VFR will prevail elsewhere. AIRMET Sierra is in effect for mountain obscuration for windward Big Island. Conditions expected to improve by this afternoon. AIRMET Tango remains in effect for moderate low-level turbulence S through W of terrain due to the breezy trades, as well as for moderate turbulence between FL300-FL400 due to a jet aloft over the state. AMD NOT SKED for PMDY as equipment remains unavailable with no time table for return to service. && .MARINE... An E-W oriented surface ridge about 700 nm N of the islands will remain nearly stationary through Tuesday, supporting fresh to locally strong ENE trade winds. A Small Craft Advisory (SCA) is posted for the windier zones around Maui and the Big Island. On Wednesday and Thursday, unseasonably strong low pressure rapidly developing N of the area will weaken the high, and displace the ridge southward over the islands. Winds will respond by becoming light and variable Thursday and Friday. An extended period of elevated surf along S facing shores is underway, with numerous swell pulses expected, mainly from the SSW. A High Surf Advisory (HSA) is likely to be needed for the largest of the swells, which may not arrive until next weekend. At the moment, offshore NDBC buoys, nearshore PacIOOS buoys and surf cams indicate that the wave period of the current swell remains long, but peak energy trending down toward 15 seconds is leading to more consistent breakers as compared to yesterday. This swell has likely peaked, but will only gradually ease Tuesday before additional long-period swells arrive. A small NW swell is expected Monday and Tuesday, with the potential for a small follow-up later in the week. A small N swell is also possible next weekend. Trade winds will continue to generate short-period wind waves the next couple of days, leading to choppy surf along exposed E facing shores. Wind waves will diminish significantly after Wednesday. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...JVC AVIATION...TS MARINE...Birchard