Surface high pressure will continue to build north of the state through Wednesday and bring moderate to locally breezy easterly trade winds. Brief passing showers will favor windward and mountain areas, mainly during the overnight and early morning hours. Late Wednesday through this weekend, trade winds will ease slightly and veer to a more east- southeast direction, shifting shower activity toward east and southeast facing slopes of most islands. However, overall rainfall amounts are expected to remain limited. An approaching front may bring unsettled wet weather by early- to mid next week.
An IR satellite imagery loop from this morning shows a swath of mid and high clouds slowly dissipating over Maui and the Big Island as a weak upper level disturbance fades. At the surface, a large area of high pressure far north and northeast of the state has become well established. This feature has acted to tighten the surface pressure gradient and strengthen easterly trades to moderate to locally breezy. As is typical with this flow regime, scattered light to moderate showers have mainly affected windward and mauka areas of the islands with rainfall accumulations generally ranging from a few hundredth of an inch to around a half of an inch. Little change is expected through Wednesday with the high to the north continuing to drive moderate to locally breezy easterly trades with night and early morning scattered showers focused mainly along windward and mauka locations.
Thursday through this weekend, winds will begin to veer east southeast and ease as a long wave trough deepens in the central North Pacific and the aforementioned surface high north of the region slowly moves east. Models show the inversion height rising by the few thousand feet, but moisture remains limited. Thus, there may be a few showers that form over the interior regions as afternoon sea breezes develop, but nothing of significance.
Early- to mid next week, both the GFS and ECMWF begin to nudge the deep trough closer towards Hawaii and push an associated cold front in from the west. If the occurs, expect unsettled wet weather and gusty southerly winds ahead of the front. However, confidence in the storm details remains low at this time due to both timing and intensity differences between models.
Clearing skies will gradually continue across most of the island chain today as high pressure and trades gain a stronger influence over the area. MVFR conditions are possible along windward sites to start off the period, however cigs are expected to improve over the next 24 hours. Cannot rule out stray shower activity along windward sites due to the strengthening trade wind pattern, however. Elsewhere, expect moderate trade breezes and VFR conditions.
AIRMET Tango remains in effect for moderate upper-level turbulence between FL290 and FL370 across the islands, however as this ongoing system dissipates, this turbulence is expected to diminish. Light icing is also possible between FL130 and FL230 from Maui to the Big Island through the early morning, however as these high clouds continue to move out from the area, the icing threat is expected to dissipate.
Building surface high pressure north of the islands will strengthen and drift northeast through the week bringing moderate to locally strong east to east south east winds through Wednesday. A Small Craft Advisory (SCA) is currently in effect for the windier waters and channels around Maui County and the Big Island through this afternoon. As the winds veer, the SCA will expand to add Maui County and Big Island windward waters through Wednesday afternoon. Looking towards the ending of the week, winds look to veer to the east southeast and weaken slightly as a upper trough and surface front approach from the northwest.
The current moderate medium period northwest swell gradually declined overnight and will continue to trend down through the rest of the week. The next small to moderate northwest swell looks to build in Saturday and hold through the weekend. Surf along east facing shores will remain choppy as fresh trade winds redevelop and expand upstream of the state. This will keep surf along exposed east-facing shores somewhat elevated.
Surf along south-facing shores will remain small to tiny, with no significant swells forecast for at least the next several days.
A Coastal Flood Statement has been issued through Wednesday morning due to the peak monthly high tides combined with water levels that are running higher than predicted. This may lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is expected around the daily peak tide early this morning and Wednesday morning.
Small Craft Advisory from 6 PM this evening to 6 PM HST Wednesday for Maui County Windward Waters-Big Island Windward Waters.
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
