| Current Conditions | ||
| Temp |  | 4.1 C |
| RH | | 5 % |
| Wind | | WSW 14 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 362 FXHW60 PHFO 260627 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 827 PM HST Thu Apr 25 2019 .SYNOPSIS... A cold frontal system passing through the Central Pacific will weaken the high pressure ridge north of the islands. Wind speeds will weaken and veer towards the southeasterly direction tomorrow. Shower activity will increase this weekend across the state with locally heavy showers and thunderstorms possible on Sunday and Monday. Trade winds return on Tuesday with more stable weather conditions as a high pressure ridge builds back in north of the state. && .DISCUSSION... The high pressure ridge north of the islands will weaken rapidly this evening as a cold frontal system moves across the Central Pacific basin. Wind speeds will weaken tomorrow and veer towards a more southeasterly direction. Elevated showers may develop along the east to southeast slopes of both Maui and the Big Island from Friday afternoon to Friday evening. Isolated to scattered windward and mountain showers will linger over the rest of the state. The weather pattern gradually changes this weekend with light winds allowing land and sea breezes to develop over all islands ahead of a cold front that will likely stall northwest of the island chain. A broad upper level trough pattern will lead to more unsettled weather conditions from Saturday into Sunday with clouds and scattered showers developing over island interior sections by afternoon. On Sunday night a stronger short wave trough aloft moves into the state from the northwest direction. This trough will create unstable conditions with deeper convective showers, leading to locally heavy rainfall and thunderstorm activity. The western islands will feel the impacts of this trough on Sunday night with deeper showers spreading southeastward down the island chain to the rest of the state on Monday. By next week Tuesday we return to a moderate trade wind weather pattern as the low pressure system drifts eastward and another high pressure system moves into the Central Pacific. Some clouds and showers associated with the stalled cold front may drift into Kauai and Oahu on the trades trending toward the windward and mountain sections of each island. Trade wind weather will continue through the first half of next week. && .AVIATION... Trade winds will be in the light to moderate range through tonight as a high pressure ridge remains north of the state. However, with a front approaching the area from the northwest, winds will begin to veer to the southeast Friday. VFR will prevail, with only isolated areas of showers and lower ceilings in windward and mauka sections over the individual isles. No AIRMETs are currently in effect. && .MARINE... Light to moderate trades will continue through Friday before becoming light and variable over the weekend. An approaching front from the west will nudge the ridge north of the islands away, and replace it with light and variable winds, that will last through early next week. Under this light wind regime, expect daytime sea breeze along the coast and nighttime land breeze. Expect an uptick in showers as well area-wide, especially during the afternoons and evenings. Further more, an upper level trough will bring a slight chance of thunderstorms over the surrounding waters for Sunday through Monday. Small but steady surf will continue along north facing shores through the weekend due to a couple of recent systems passing north of the islands. The current north swell will begin to veer north- northeast on Friday and will hold through the weekend. A moderate size northwest swell is expected to build through the day Sunday and peak Sunday night into Monday and gradually ease through midweek. Surf will remain well below advisory levels. For the south facing shores, a similar trend will continue during the first half of the period, with a series of long- period pulses, spaced a couple of days apart. For the long range, more small long- period swells are expected through next weekend. As the trade winds become even lighter, so will the locally generated trade wind swell. Therefore, expect small surf along the east facing shores over the weekend and into early next week. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Bohlin AVIATION...JT MARINE...Lau Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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