Trades will give way to southeast winds later today as an upper level ridge axis moves across the state. Showers will be light and mainly in windward and mauka areas. A weakening cold front will move into the western part of the state Wednesday, but confidence is low on how far into the state it will get. Rainfall chances will increase in western counties Wednesday through Friday, and perhaps throughout the state. There is a chance that increased showers could linger through next weekend.
Satellite showed areas of low clouds moving toward the state from the east-northeast under the influence of trade winds early this morning. There was just enough moisture for isolated light showers moving into some windward areas, but any precipitation amounts will be light, a few hundredths of an inch at most.
A surface high far to our northeast will move even farther northeast today, helping to shift our winds around to become more southeasterly. Predominantly dry and stable conditions are expected to persist through Tuesday, with only a few light showers along windward and southeast slopes and coasts. The east- southeast to southeast surface winds will gradually weaken over the next few days as a front approaches the region from the northwest.
Things change more significantly Wednesday, when a front will approach from the northwest. Driven by an upper level trough, reaching Kauai County Wed morning, then Oahu in the afternoon, and Maui County in the evening. Models diverge at this point, with important differences. Ensemble members show some solutions taking the front through Big Island, while others stall it out and begin to move it back to the west. But the speed at which it moves back west and the amount of moisture associated with the remains of the front vary amongst the solutions. At this point, all we can really say is that the chance of precipitation increases from west to east across the state Wednesday into Thursday, with an increased chance of showers likely remaining elevated over some parts of the state beyond Thursday. Clarity on this part of the forecast will probably take several more days as the models slowly converge on a solution.
Moderate to locally breezy trades are expected to continue this morning before becoming southeast in most areas this afternoon. Brief, isolated to scattered showers are forecast over windward and mauka areas this morning, but will decrease this afternoon. Brief MVFR conditions are possible within these showers, with VFR conditions prevailing elsewhere.
AIRMET Tango remains in effect for low-level turbulence downwind of island terrain today. Additionally, AIRMET Tango is also in effect for tempo moderate turbulence between FL240-FL320. This turbulence is expected to be out of the area around the time of the next issuance and will likely be dropped at that time. However, moderate upper-level turbulence could return to the area again tonight.
The morning package continues a Small Craft Advisory (SCA) to the typical windier coastal waters, and adds most of the remaining coastal waters as the incoming northwest swell will bring SCA level seas to exposed areas today and into tonight. A High Surf Advisory (HSA) has also been posted to the north and west facing shores of Niihau, Kauai and Oahu, and the north facing shores of Molokai and Maui.
High pressure to the north of the state will continue to move to the east as a cold front moves towards the islands today. With the high pressure to the north, moderate to locally strong trade winds will continue today. As the cold front advances to the east towards the islands, winds will weaken and veer to the southeast. The front is expected to enter the offshore waters Tuesday, and will bring the possibility of thunderstorms to the northern offshore waters Tuesday through Thursday. The front is expected to reach the northwest coastal waters late Tuesday, and move over the central waters Wednesday where it will linger during the second half of the week.
The new moderate, long period, northwest swell reached the buoys to the northwest of the islands around midnight, and will reach Kauai later this morning. This swell will cause surf to rise rapidly along north and west facing shores. A High Surf Advisory (HSA) has been posted for the effected shores of the smaller islands. This swell is expected to peak in the islands this afternoon, with surf dropping below HSA levels tonight. Another moderate, long period, northwest swell is expected to arrive in the islands Tuesday, and linger through the middle of the week. This swell will maintain elevated surf along north and west facing shores.
The moderate to locally strong trade winds today will maintain rough and choppy surf along east facing shores. Additionally, some east facing shores sensitive to northerly swells may be experiencing a slight uptick in surf heights today as a fading north swell lingers. As winds weaken and veer to the southeast ahead of the incoming front, surf will lower along east facing shores. There are no noteworthy swells for the next few days for south facing shores.
High Surf Advisory until 6 AM HST Monday for north and west facing shores of Niihau, Kauai, and Oahu, and north facing shores of Molokai and Maui.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel- Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters- Maui County Leeward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters.
