Sunrise 5:47 AM   Sunset 6:57 PM Moonrise 10:56 AM   Moonset 12:00 AM

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PHZ119 Maalaea Bay- 938 Am Hst Mon May 13 2024
Rest of today - North winds 15 to 20 knots. Seas to 2 feet or less. Isolated showers late this morning, then scattered showers this afternoon. Tonight - North northeast winds to 15 knots. Seas to 2 feet or less. Isolated showers in the evening, then scattered showers after midnight. Tuesday - North northeast winds to 15 knots, veering to south in the afternoon. Seas to 2 feet or less. Isolated showers in the morning, then scattered showers in the afternoon. Tuesday night - Winds variable less than 10 knots. Seas to 2 feet or less. Isolated showers in the evening, then numerous showers with isolated Thunderstorms after midnight. Wednesday - Winds variable less than 10 knots, becoming south to 10 knots in the afternoon. Seas to 2 feet or less. Occasional showers with isolated Thunderstorms. Wednesday night - South winds to 10 knots. Seas to 2 feet or less. Occasional showers with isolated Thunderstorms. Thursday - South winds 7 to 10 knots, becoming variable less than 10 knots. Seas to 3 feet. Occasional showers with isolated Thunderstorms. Friday - Winds variable less than 10 knots. Seas to 2 feet or less. Isolated Thunderstorms through the night. Numerous showers.
winds and seas higher in and near tstms.

PHZ100 938 Am Hst Mon May 13 2024
Synopsis for hawaiian coastal waters - A new cold front will approach the islands from the northwest Tuesday night. The front will move into the western islands Wednesday night and Thursday, then weaken into a trough and shift westward Friday.

FXHW60 PHFO 132015 AFDHFO

Area Forecast Discussion National Weather Service Honolulu HI 1015 AM HST Mon May 13 2024

SYNOPSIS
Light southeasterly winds, afternoon sea breezes and weak troughing aloft will produce brief periods of slow moving showers over most islands through Tuesday. Some of these showers may become heavy at times especially along the eastern slopes of Oahu and Maui, and the southeastern slopes of the Big Island. On Wednesday the weather pattern trends more unstable as southerly winds develop over the state in response to a kona low approaching the islands from the north. Deep unstable tropical moisture will move over all islands from the south, resulting in periods of heavy rainfall, thunderstorms and strong gusty winds. The threats from flooding and thunderstorms will be elevated for all islands from Wednesday into the weekend.

DISCUSSION
An upper level low continues to linger north of the state and continues to produce unstable conditions over the state. A surface trough over the western end of the state will bring light east to southeast winds today and light southeast to south winds on Tuesday. Overall the weather pattern looks fairly similar today and tomorrow with heavy showers possible each afternoon due to the sea breeze convergence. The most likely area for heavy rain will be over interior and mountain areas. With steep low level lapse rates and ample moisture (precipitable water values of 1.58 inches) as seen on the 12Z sounding from Lihue should allow for slow moving heavy downpours today. Currently, heavy showers are already ongoing across windward Oahu, where we have a Flash Flood Warning and we are seeing heavy showers starting to develop over other parts of the state. With the heaviest rain expected over interior and mountain areas, please remember that flash flooding can occur well downstream from the mountains in areas where it may not be even raining. Although the threat for heavy rain will continue to exist the next few days, a more widespread rain event is expected during the second half of the week.

A strong kona low will develop north of the state and its associated frontal boundary will heavily impact the state during the second half of the week. The frontal boundary will move into the state Tuesday night into Wednesday with increasing chances of heavy rain as deep tropical moisture moves in from the south. By Wednesday night, precipitable water values will likely increase over 1.8 inches across parts of the state and the frontal boundary is expected to stall somewhere around Oahu and Maui County based on the latest guidance. Where this moisture boundary stalls (late Wednesday through Friday), will be the area where there will be significant potential for flash flooding.

Several threats are likely in this weather pattern from Wednesday onward including heavy rain with flooding, thunderstorms in the strong to severe range, and strong gusty winds. The severe thunderstorm threat will favor the western islands closer to the approaching surface front/trough, the upper level cold pool and the strongest wind shear. The forecast guidance over the past few days suggests these threats will last for several days from Wednesday through Friday with even deeper moisture moving in from the south on Saturday. Latest guidance is showing deep tropical moisture with precipitable water values of over 2 inches moving into the western half of the state on Saturday. This will increase the threat of flash flooding, especially over Kauai and Oahu on Saturday. Long story short, this is a strong kona low event that will last for many days (starting Wednesday and persisting through the weekend) and will likely produce record rainfall in many areas for the month of May and will impact many people. Please stay tuned to the latest forecast as we fine tune the details.



AVIATION
Lingering instability aloft combined with a moist southeasterly flow will allow for a few SHRA across the state through the forecast period. Winds will remain light enough to allow for a land/sea breeze pattern where clouds and SHRA will build up over island interiors during the afternoon/early evening hours and clear out overnight. MVFR conds are expected in heavier SHRA, with brief IFR conds possible.

AIRMET Sierra for mtn obsc is in effect over east facing areas of Oahu and Kauai. AIRMET Sierra for IFR conds may also be needed for the southeastern slopes of the Big Island later today as showers periodically become heavy.

MARINE
The air mass over the state will remain moist and unstable, creating a favorable environment for locally heavy showers and possible thunderstorms. Light to locally moderate southeasterly flow will hold over the next twenty-four hours.
Winds will shift to the south Tuesday night when a new cold front will approach the islands from the northwest. The front will move into the western islands Wednesday night and Thursday, then weaken into a trough and shift westward Friday. Light to moderate northwest winds may briefly develop behind the front over the far western end of the state, otherwise moderate southerly winds should prevail into the weekend.

Surf along south facing shores will slowly decline today and tonight. A series of overlapping, long-period south swells will then move through the islands Tuesday into the weekend. This will be a long lived south shore event, with multiple overlapping pulses. Surf may approach High Surf Advisory criteria on Thursday.

A small, long-period northwest swell peaked early this morning will slowly decline through tomorrow. A new northwest swell will then arrive on Wednesday. This will bring moderate sized surf moving into north facing shores Wednesday night through Friday.

Surf along east facing shores will remain well below normal levels through the weekend.

HFO WATCHES/WARNINGS/ADVISORIES
None.

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Kahului
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Kihei
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Kihei, Maui (Hawaii) (2), Tide feet

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