High Surf Advisory

...HIGH SURF ADVISORY FOR SOUTH FACING SHORES OF ALL HAWAIIAN ISLANDS... .A long-period south swell generated by a powerful long-lived storm in the southern hemisphere will gradually decline tonight through Tuesday night. ...HIGH SURF ADVISORY REMAINS IN EFFECT UNTIL 6 PM HST TUESDAY...

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4-6 foot
3-5+ foot
4-6+ foot
3-5+ foot

High pressure building northwest of the marine area will lead to a gradual increase in the trades through the weekend. Winds should remain below Small Craft Advisory levels through Sunday, with moderate to locally strong trade winds potentially requiring a SCA for the windier zones around Maui and the Big Island developing Sunday night and continuing through much of next week.

A persistent upper-level trough over the area will keep conditions unstable through the weekend, bringing the potential for heavy showers and thunderstorms, particularly over the waters surrounding Maui and the Big Island.

The latest nearshore NDBC buoys show the incoming south swell continuing to inch up early this morning. This swell is expected to produce well above normal surf right through early next week. The long period south swell will continue to build today, then peak tonight and Sunday, before lowering slightly for Monday. As a result, a High Surf Advisory remains in effect for south facing shores of all islands through 6 PM Monday. Re-enforcing south swells will keep south shore surf elevated through much of next week, with another Advisory level event possible by late next week or next weekend.

Elsewhere, surf heights will remain below advisory levels through the middle to latter part of next week. A moderate short period north-northwest swell is expected to hold through tonight, then gradually drop Sunday through early next week.

Hawaii Wave Height Model

Tide Predictions

High tide at Kahului was 1.54 foot at 2:00 PM early this afternoon, dropping to a low of 0.59 foot at 2:00 PM early this afternoon, then rising to a high of 2.20 foot at 2:00 PM early this afternoon, before once again dropping to a low of 0.45 foot at 2:00 PM early this afternoon.

The sunrise was at 06:22 am this morning and will set at 05:58 pm this evening. The Moon is currently 11 days old, and is in a Waxing Gibbous phase. The next Full Moon will occur at 4:47 PM on Wednesday, October 24th.

Hawaii Wind Report

Maui Weather

°/°
Wind: n/a at 0 mph
Sunrise:
Sunset:
current observations as of 6pm October 22nd, 2018

Weather Outlook for Saturday, 20th October 2018

Summary

A weak trade wind flow will gradually strengthen through Sunday night. A disturbance at the upper levels of the atmosphere will lead to some unsettled weather with thunderstorms across mainly the eastern half of the island chain, but especially for the Big Island over the rest of the weekend. Locally strong trades return by Monday and persist through at least the middle of next week. Showers riding in with the trades will be favoring the windward an mountain areas. The frequency of these trade showers will increase overnight, then diminish in the morning.

Detailed Discussion

An unstable trade wind flow will likely persist through the eastern part of the island chain for the remainder of the weekend as an upper level trough makes it way gradually eastward. The light to moderate trades will be gaining strength through Sunday night, reaching locally strong by daybreak Monday. The strengthening trades is in response to a front dissipating 450 miles north of Kauai. The trades are shallow now, but will deepen as the upper trough moves eastward.

The overnight heavy showers and thunderstorms, including the current activity, over windward Maui have led to the issuance of a Flash Flood Watch for Maui County that goes through 6 pm HST this afternoon. These flaring heavy showers and thunderstorms have been the pattern throughout the night, and are at it once more, requiring a Flood Advisory for windward Maui the second time around overnight. The advisory is good to until 5 am HST. But the ground is saturated and any more heavy rains will lead to flash flooding and mud slides, etc. Thus, the watch was extended to Maui County, that include Moloka`i and Lana`i, and Kaho`olawe.

Water vapor imagery shows the upper level short wave trough axis nearing Oahu from the west at 3 am HST, with dense layered clouds draped over Maui County and the Big Island. The upper trough will be slowing down as it makes its way across Maui County this afternoon through tonight. The trough axis is expected to clear the Big Island by Sunday afternoon as per GFS, or after midnight Sunday evening as per ECMWF. In essence, by Monday morning.

With the upper trough having cleared Kauai, the weather for Kauai should be fine. The trades will still be weak enough that will lead to some interior afternoon showers. This morning sounding shows a higher precipitable water value of 1.53 inches. The air mass should be more stable there by the time of max heating this afternoon. Oahu should also be out of the area favorable for thunderstorms or heavy showers by perhaps mid morning. After last evening’s deluge over parts of windward Oahu, things have quieted down considerably in the last 2 hours or so.

We look forward to the return of more normal benign trades area- wide by Monday, and last through the new work week. The two models are still showing an area of tropical moisture slated to reach the Big Island and Maui around Tuesday that will lead to a slight uptick in trade showers. It is less of an impact compared to that of 24 hours ago by the models. Also, there are no upper level trough to enhance this tropical moisture.

Central Valley (Kahului, Spreckelsville):

HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST MONDAY… …FLASH FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON. Mostly sunny in the morning then becoming partly sunny. Scattered showers and chance of thunderstorms. Highs around 85. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Leeward West (Lahaina, Ka`anapali):

HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST MONDAY… …FLASH FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON. Mostly sunny in the morning then becoming partly sunny. Scattered showers and chance of thunderstorms. Highs 81 to 86. Northeast winds up to 15 mph. Chance of rain 50 percent.

Windward West (Wailuku, Waiehu):

FLASH FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON. Mostly cloudy. Scattered showers and chance of thunderstorms in the morning, then showers likely and chance of thunderstorms in the afternoon. Locally heavy rainfall possible in the morning. Highs 69 to 84. Northeast winds up to 15 mph. Chance of rain 70 percent.

Windard Haleakala (Hana, Haiku, Makawao):

HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST MONDAY… …FLASH FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON. Mostly cloudy with showers likely and chance of thunderstorms. Locally heavy rainfall possible in the morning. Highs around 81 at the shore to around 66 at 5000 feet. East winds up to 15 mph. Chance of rain 70 percent.

Leeward Haleakala (Kihei, Wailea, Makena):

HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST MONDAY… …FLASH FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON. Mostly sunny in the morning then becoming partly sunny. Scattered showers and chance of thunderstorms. Highs around 85 at the shore to 67 to 75 upcountry. Northeast winds up to 10 mph. Chance of rain 50 percent.

Haleakala Summit

FLASH FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON. Partly sunny with scattered showers and chance of thunderstorms. Highs around 59 at the visitor center to around 55 at the summit. Light winds. Chance of rain 50 percent.

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