Sunrise 5:46 AM   Sunset 6:57 PM Moonrise 12:44 PM   Moonset 1:12 AM

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PHZ119 Maalaea Bay- 915 Pm Hst Tue May 14 2024
Rest of tonight - South winds 7 to 10 knots. Seas to 2 feet or less. Scattered showers. Wednesday - South winds to 10 knots, rising to 15 knots in the afternoon. Seas to 2 feet or less. Scattered showers. Wednesday night - South winds 15 to 20 knots. Seas to 2 feet or less. Scattered showers in the evening, then numerous heavy showers after midnight. Thursday - South winds 10 to 15 knots. Seas to 3 feet. Numerous heavy showers. Isolated Thunderstorms in the afternoon. Thursday night - South winds 7 to 10 knots in the evening, becoming variable less than 10 knots. Seas to 3 feet. Isolated Thunderstorms in the evening. Scattered showers. Friday - Winds variable less than 10 knots, becoming southeast 7 to 10 knots in the afternoon. Seas to 2 feet or less. Isolated showers. Friday night - East winds 7 to 10 knots. Seas to 2 feet or less.Saturday - East northeast winds 10 to 15 knots. Seas to 2 feet or less. Isolated showers through the night. Sunday - East northeast winds 10 to 15 knots. Seas to 2 feet or less.
winds and seas higher in and near tstms.

PHZ100 915 Pm Hst Tue May 14 2024
Synopsis for hawaiian coastal waters - A cold front approaching the state from the west will advance eastward and stall over oahu by late Thursday. The front will then weaken shift westward Friday. Slight chance of Thunderstorms starting Wednesday night and continuing into the weekend.

FXHW60 PHFO 150808 AFDHFO

Area Forecast Discussion National Weather Service Honolulu HI 1008 PM HST Tue May 14 2024

SYNOPSIS
A kona low will develop about 600 miles north of Kauai overnight into Wednesday, then intensify and meander around well northwest of the islands into next week. The kona low will turn our local winds southerly, pulling copious moisture from the deep tropics over the islands. A slow moving band of downpours and a few thunderstorms is expected to develop near Oahu and Maui county Wednesday night into Thursday, then slowly shift westward toward Kauai by Friday. Excessive rainfall and flash flooding will certainly be possible. Other areas away from the main band could see spotty downpours and localized flooding problems as well. The weather over the Aloha State this weekend and beyond will depend highly on the later evolution and movement of the kona low far to our northwest.

DISCUSSION
A strong digging shortwave trough is quite clear on water vapor imagery this evening well to the NNW of the islands, and this feature will be the one to initiate cyclogenesis approximately 600 mi N of Kauai. Background low level southerly flow has already started creeping our dewpoints upward, approaching or exceeding 70 at some lower-elevation stations. Both the GOES-derived and CIMSS-MIMIC total precipitable water fields are showing a large wedge of relatively moist air pushing northward across the area surrounding Hawaii, with even deeper ITCZ moisture well to our S beginning to creep N under the influence of the sharply digging trough aloft.

In the short term, numerous disorganized showers and the odd, brief thundershower or two are pushing northward across Oahu and Maui county, with the Big Island on the periphery of this area and Kauai mostly quiet so far this evening. The convection-allowing models (CAMs) and HRRR suggest that this will continue to be the case overnight, and also showing the need to keep an eye on the ESE flow into the Kau district of the Big Island.

As the kona low develops, the convergence band over the islands will sharpen, and the focus for heavier spotty showers will shift westward for a time on Wed. Although the CAMs have minor differences in the details, there is good agreement about a fairly solid band of heavy showers and embedded thunderstorms developing somewhere near or over Oahu Wed night and lingering into Thu. The HRRR shows increasing probabilities for excessive rainfall rates focusing on Oahu as an area of favorable upper level jet stream diffluence spreads over the low level convergent band. There are still some probs for intense rainfall on Maui county, but a subtle westward shift in the guidance with time has been noted over the last few HRRR runs.

One other thing to note is the risk of some gusty downslope winds on the normal-windward side of the islands. The models don't seem to be super-stoked about the possiblity for damaging downslope winds, but some gusts over 30 knots appear possible on Wed into Wed night.

The global models and CAMs show that the band may break up or weaken a bit by Thu night as the best diffluence and stronger shortwave energy shifts NE of the islands. Heavy showers will still be possible but they may become more spotty and less organized for a time before reintensification starting Friday.
One of the big questions that remains will be how far W will the band be when it reintesifies under stronger upper level diffluence Fri into the weekend. The NBM thunderstorm probabilities show values increasing again near Kauai on Friday before shifting westward to the coastal and offshore waters W of Kauai Fri night.
Global model rain rates increase quite a bit within the band this weekend, but by then hopefully the heaviest rain is falling out over the water. Still, the models can change on these details and we'll need to keep an eye on this.

The global models show that the middle and eastern islands this weekend will have an odd combination of very moist air, with precipitable water near 2 inches...but also a low level subsidence inversion that may try to keep somewhat of a lid the moisture.
Nevertheless, with ESE or SE flow continuing, there should be some fairly prolific afternoon showers in any areas shadowed by the background flow. Kauai remains a big question mark during this period.

There's considerable uncertainty after the weekend, with lingering moisture gradually diminishing and the kona low far to the north likely weakening, leaving a surface trough behind W of the islands.
There should be a continuing trend toward more settled weather statewide, with weak mid-level ridging eventually trying to build in. In the meantime, there will be a daily chance of spotty heavy showers, mainly in the afternoons and evenings.

AVIATION

The aviation weather forecast will continue to be active through the rest of the week, especially as a kona low develops to the northwest of the island chain. Showers and thunderstorms will bring the potential for periodic MVFR or lower conditions on and off throughout the period. Southerly winds will be light overnight before picking up tomorrow. Moderate winds are expected with higher gusts possible within/near heavy showers or thunderstorms.

AIRMET Sierra is in effect for all the smaller islands and windward Big Island for mtn obsc. Sierra may be needed for IFR conds and Tango for turb as the kona low gets closer and conds deteriorate.

MARINE
Low pressure developing north of Kauai will usher a cold front toward the state from the northwest this evening. The front will advance eastward until stalling over Oahu late Thursday and weakening. The remnant boundary will then drift west during the remainder of the week. Heavy showers and isolated thunderstorms are expected along and ahead of the front.

A series of overlapping, long period S swells will maintain near to below average surf along S facing shores through the near term. Renewed energy out of the southerly quadrant will then fill in late tomorrow night bringing above average surf by Thursday.
Surf remains elevated in through the weekend.

A small medium period NW swell is filling in this evening and will peak on Wednesday. By Wednesday night, a short period fresh NW swell associated with the developing low will spread into the area. This swell is forecast to peak near to just below the High Surf Advisory threshold Thursday into Friday.

West facing shores see a bump in surf through the week due to overlapping NW swell and S swells wrapping into exposed areas.
Surf along E facing shores remains well below normal through the weekend.

HFO WATCHES/WARNINGS/ADVISORIES
Flood Watch from 6 AM HST Wednesday through Friday evening for all Hawaii islands-

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Kuheia Bay
Click for Map
Wed -- 01:11 AM HST     Moonset
Wed -- 01:49 AM HST     First Quarter
Wed -- 05:42 AM HST     -0.01 feet Low Tide
Wed -- 05:49 AM HST     Sunrise
Wed -- 11:58 AM HST     0.87 feet High Tide
Wed -- 12:43 PM HST     Moonrise
Wed -- 03:47 PM HST     0.50 feet Low Tide
Wed -- 06:56 PM HST     Sunset
Wed -- 10:41 PM HST     1.63 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Kuheia Bay, Kahoolawe Island, Hawaii, Tide feet

Kihei
Click for Map
Wed -- 01:11 AM HST     Moonset
Wed -- 01:49 AM HST     First Quarter
Wed -- 05:05 AM HST     0.20 feet Low Tide
Wed -- 05:48 AM HST     Sunrise
Wed -- 11:09 AM HST     1.00 feet High Tide
Wed -- 12:42 PM HST     Moonrise
Wed -- 03:31 PM HST     0.54 feet Low Tide
Wed -- 06:56 PM HST     Sunset
Wed -- 10:42 PM HST     1.83 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Kihei, Maui (Hawaii), Tide feet

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