Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
985 FXHW60 PHFO 060127 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 327 PM HST Sun May 5 2024 .SYNOPSIS... Breezy trade winds will continue into Monday, then decrease to moderate speeds late Monday into Tuesday. An upper-level disturbance passing through the islands will keep enhanced trade showers in the forecast through Monday. Additional bands of moisture, along with another upper disturbance, will keep generally wet weather in place for all islands into next weekend. && .DISCUSSION... Water vapor satellite imagery this afternoon shows a weakening upper-level low just west of Kauai, drifting slowly eastward. A portion of the subtropical jet stream remains near the islands this afternoon, but is forecast to weaken over the next day or so. Winds at the Big Island Summits have been borderline advisory level today, but the overall trend this afternoon has been down. Therefore, the Wind Advisory for the summits has been cancelled. At the surface and lower elevations, a 1029 mb high remains far north of the island chain and will continue to produce breezy easterly trade winds across the state into Monday. By Monday afternoon, trade wind speeds transition to more moderate levels as the high moves off to the east. Expect moderate easterly trade winds to continue through the rest of the week. Current visible satellite and radar imagery show scattered low clouds and showers moving into windward areas on the trades, with some showers making it over to leeward sides at times. Wetter than normal conditions remain in the forecast for all islands through much of this week. Enhanced showers will continue through Monday night as the weakening upper level disturbance swings through the island chain from west to east. Showers will be heaviest and most widespread over windward areas and during the overnight and early morning hours. There also appears to be enough instability around on Monday for some convective activity, so have added a slight chance of thunderstorms over interior Big Island for Monday afternoon. While Tuesday will trend slightly drier, more wet trade wind weather is in store Wednesday through Friday, as the remnant moisture from an old East Pacific cold front drifts into the islands. Another upper-level trough sweeping in from the north on Thursday and Friday will likely keep enhanced showers in the forecast into next weekend. && .AVIATION... Breezy easterly trade winds will persist into Monday, with clouds and showers favoring windward areas. An upper low will move east across the islands tonight into Monday, along with an incoming band of showers, will result in increasing rainfall tonight particularly across windward sides of Kauai, Oahu and Big Island. AIRMET Sierra for mountain obscurations will be possible later tonight across windward areas. AIRMET Tango is in effect for moderate turbulence below 8000 feet downwind of island terrain due to the winds. Additionally, moderate turbulence aloft (FL280-FL380) is expected through tonight. && .MARINE... A 1030 mb high centered over 800 nm north of the state is maintaining fresh to near gale force trade winds, and a Small Craft Advisory (SCA) remains in effect for all waters through tonight. Trades will gradually ease late tonight through Tuesday as the high moves eastward. As a result, the SCA is scheduled to be scaled back to the typically windy waters around the Big Island and Maui County by Monday morning and may be dropped entirely late Tuesday or Wednesday. Expect gentle to locally fresh trade winds to prevail Wednesday through Friday as a trough develops then lingers north of the islands. In addition, a few heavy showers will be possible tonight and Monday. Pulses of south to southwest swell are due this week, with High Surf Advisory (HSA) conditions expected by Thursday. In the short term, the bulk of a south swell will be passing east of Hawaii, but the PacIOOS buoy off of Lanai did pick up on some increase in long period energy late this morning. As this swell fills in tonight, south shore surf may rise to around May average through early Monday, then decline late Monday through Wednesday. Forerunners from a larger and longer lived south-southwest swell will arrive Wednesday, and surf is expected rise to the HSA level during the peak of the swell Thursday and Friday. A pair of small northwest swells will move through over the next several days. As the current swell of around 2 feet at 12 to 13 seconds declines overnight, a reinforcing small swell of around 3 ft will fill in through Monday, peak Tuesday, then decline late Tuesday and Wednesday. Wind-driven waves of 8 to 9 feet at 9 seconds will maintain rough east shore surf above the May average into Monday. As trade winds decline over the next few days, these seas will gradually decline to around May average by Tuesday, then drop to below average for the rest of the week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel- Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Big Island Windward Waters. Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...TS AVIATION...Foster MARINE...Wroe