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PHZ122 Big Island Windward Waters- 958 Am Hst Thu Nov 30 2023
.small craft advisory in effect through late this afternoon...
Rest of today..East winds to 25 knots. Wind waves to 4 feet. Northwest swell 4 feet. Heavy showers with isolated Thunderstorms.
Tonight..East winds to 25 knots. Wind waves to 5 feet. Northwest swell 4 feet. Numerous heavy showers with isolated Thunderstorms.
Friday..Southeast winds to 25 knots. Wind waves to 5 feet. Northwest swell 3 feet. Numerous heavy showers in the morning. Isolated Thunderstorms. Scattered heavy showers in the afternoon.
Friday night..Southeast winds 20 knots. Wind waves to 5 feet. Northwest swell 3 feet. Scattered showers in the evening. A slight chance of Thunderstorms. Isolated showers after midnight.
Saturday..East winds 20 knots. Wind waves to 4 feet. Northwest swell 3 feet. Scattered showers with a slight chance of Thunderstorms.
Saturday night..East winds 20 knots. Wind waves to 4 feet. Northwest swell 5 feet. A slight chance of Thunderstorms in the evening. Scattered showers.
Sunday..East winds 15 knots, rising to to 25 knots. Wind waves around 4 feet. Northwest swell 6 feet. Scattered showers.
Monday..East winds to 25 knots. Wind waves around 4 feet. Northwest swell 6 feet. Scattered showers.
winds and seas higher in and near tstms.

PHZ100 958 Am Hst Thu Nov 30 2023
Synopsis for hawaiian coastal waters.. A kona low west of kauai has maintained moderate southeast winds. Periods of heavy showers and isolated Thunderstorms will occur through Friday in association with this low. The low will weaken into a trough over the weekend with ridging building in north of the island chain.

FXHW60 PHFO 301936 AFDHFO

Area Forecast Discussion National Weather Service Honolulu HI 936 AM HST Thu Nov 30 2023

SYNOPSIS
A kona low west of the islands will bring a continued threat for heavy rain and flooding through Friday. Isolated thunderstorms are also possible, a few of which may be strong. Conditions will improve during the weekend into early next week as drier air moves in and trade winds return.

DISCUSSION

The islands remain entrenched in a pattern of deep cyclonic flow around the eastern periphery of a mature kona low. PWATs well in excess of 2" are making inroads into the state from the east already having engulfed the Big Island and Maui. This moisture plume will advance westward during the next 24 hours increasing the available moisture for heavy rainfall to the remainder of the state.
Convection perking up south of Kauai into the Kauai channel represents roughly the western edge of this deeper moisture and will likely serve as a focus for heavy rainfall as the day progresses, the primary uncertainty being its potential to move over land.
Latest radar trends suggest with low (Oahu) to moderate (Kauai)
confidence that heavy rain potential will increase during the next couple of hours.

Superposition of mid-level divergence and impressive right entrance dynamics will continue to provide strong large scale forcing for much of today. This will in turn favor persistence of heavy rain for at least the next several hours in areas that have already seen several inches. In particular, radar estimates range suggest 1 to 2 feet of rain has fallen over Windward Haleakala where southeasterly flow at the surface is anchoring convection to the terrain. Rain rates in this location have been steady at at least 2"/hr with occasional pulses up to 4"/hr. Likewise, steady heavy rain is focusing over the southeast and windward slopes of the Hilo and Puna Districts of the Big Island where rain rates have been similar to those on Maui.

No updates to the remainder of the forecast. Previous discussion follows.

Previous Discussion. Deep tropical moisture pooling northward over the state due to a kona low to our west supports moist and humid conditions with southerly flow persisting into the weekend.
Satellite-derived precipitable water data reflect this and depict a large band of 2+ inch values extending northward into the area from the deep tropics. Showery conditions with periods of heavy rainfall will continue, which could lead to flash flooding where the rainfall becomes focused or anchors for a given amount of time. Given the lack of focus at the surface, expect the rainfall to develop in bands and move through periodically. Uncertainty in predicting exactly when and where these bands will develop and move through remains high. Overnight, the bulk of the activity has been focused over the Big Island and around Hana on Maui, where measured rainfall totals on the Big Island were around 2 inches in 6-Hrs through 2 AM HST. The activity on Maui has been highly localized around Hana due to anchoring, with estimated rainfall rates coming in around 3-5 inches in 3-Hrs.

In addition to the rainfall potential, enhanced kinematics associated with a band of 40+ knots of deep layer shear (0-6 km)
evolving over the western end of the state plus the added instability with lowering upper heights and forcing support a few strong storms developing today. For the Big Island Summits, areas of showers developing and lifting northward in the area will keep the potential in place for a wintry mix, which has led to the extension of the Winter Weather Advisory.

Conditions should begin to improve late in the weekend through early next week with drier air moving in and as the trades return.



AVIATION

Kona low approximately 270 nm W PHLI mov NW 5kt, with a broad belt of moist southerly tropical flow on it's E flank, will keep fairly widespread MVFR with persistent MTN OBSC and some pockets of IFR moving up over the state for the next couple of days. High resolution guidance shows the worst wx and pockets of deeper convection over the eastern end of the state today but that should settle down some by tonight. However, the weather may deteriorate overall some over western portions later today with increasing coverage of convection expected.

Aside from convection and icing associated with any TS, AIRMET for mid-level turb will also continue to be needed, plenty of PIREPS indicating up to MDT TURB in the 100-FL200 layer, and may need to expand this layer. Light icing in layered clouds has also been reported and will also continue to be a risk in the 140-FL240 layer.

MARINE

The positioning of a broad kona low located approximately 300 nautical miles west northwest of Kauai and surface high pressure off to the distant northeast will maintain moderate to locally strong southeast winds, particularly around more eastern islands, through Friday. A Small Craft Advisory is in effect for the waters east of the Kaiwi Channel with the exception of the Pailolo Channel, Maalaea Bay and southeast Big Island waters today. The kona low will fill in through the weekend and, as a series of North Pacific systems travel east within the westerlies, weak high pressure just north of the state will guarantee winds will ease and transition back to trade flow this weekend. Trades will gradually strengthen next week as high pressure builds in from the northwest.

A small to moderate, medium period northwest (320 degree) swell will peak today then gradually lower through Saturday. The next moderate size, longer period northwest (320 degree) swell will arrive and begin to fill in Saturday. This swell will peak surf to near High Surf Advisory (HSA) heights Sunday, then slowly subside Monday. A reinforcing north northwest (330-350 degree)
swell arriving Monday night could lift surf well above HSA thresholds Tuesday and Wednesday. Expect choppy conditions along south-facing shores the next couple of days due to persistent moderate to fresh southerlies in tandem with very small, medium period south swell. Less choppy east conditions can be expected over the weekend as east-facing shore surf is forecast to hold near seasonal levels before falling below December averages early next week. Strengthening trades during the middle of next week could boost east shore chop back up to above seasonal levels.

HFO WATCHES/WARNINGS/ADVISORIES
Flood Watch through Friday afternoon for all Hawaii islands-

Winter Weather Advisory until 6 AM HST Friday for Big Island Summits.

Small Craft Advisory until 6 PM HST this evening for Maui County Windward Waters-Maui County Leeward Waters-Alenuihaha Channel- Big Island Windward Waters-Big Island Leeward Waters.

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Hilo, Hilo Bay, Kunio Bay, Hawaii Island, Hawaii, Tide feet

Honuapo
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Thu -- 05:46 AM HST     2.83 feet High Tide
Thu -- 06:38 AM HST     Sunrise
Thu -- 09:52 AM HST     Moonset
Thu -- 02:03 PM HST     0.41 feet Low Tide
Thu -- 05:43 PM HST     Sunset
Thu -- 05:46 PM HST     1.01 feet High Tide
Thu -- 08:57 PM HST     Moonrise
Thu -- 10:29 PM HST     0.30 feet Low Tide
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Honuapo, Hawaii Island, Hawaii, Tide feet

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