| Current Conditions | ||
| Temp |  | -3.0 C |
| RH | | 58 % |
| Wind | | N 13 mph |
| Road | | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 213 FXHW60 PHFO 050630 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 830 PM HST Sat Feb 4 2023 .SYNOPSIS... An upper low over the state will maintain an unstable and moist airmass, which will generate showers and isolated thunderstorms, with locally heavy rainfall, through the remainder of the weekend. The upper low will weaken and exit east of the islands by Monday. Much drier and more stable conditions will filter across the state to begin the work week, while a more typical trade wind weather pattern develops across the islands into next weekend. && .DISCUSSION... Current radar shows showers remaining across the islands this evening, becoming more focused along windward slopes as locally breezy trade winds continue across the region. Radar estimates suggest locally enhanced rainfall rates remaining embedded within some of the showers this evening. The latest lightning data shows a few strikes in the vicinity of the Big Island, around 200 miles north to northeast of Hilo, in an area of enhanced instability (Showalter Index (SW) around -2c). Tonight through Sunday...the upper low will remain anchored over the state tonight, before slowly moving eastward and becoming centered across the Big Island Sunday night. This pattern will maintain deep layered moisture (PWs greater than 1.50") and modest instability (SW around 0 to -1c) across the state through Sunday afternoon. The deeper moisture and lingering instability will then become mainly concentrated across the eastern end of the state Sunday night into early Monday. Thunderstorm probabilities show the best chance for isolated storms to remain across windward zones and surrounding waters, and vicinity of the Big Island through Sunday afternoon. Drier and more stable conditions will then begin to push in across the western end of the state Sunday night into early Monday. Overall, will maintain the current forecast trend, with showers and isolated thunderstorms becoming mainly focused along windward areas and marine waters through Sunday afternoon. Monday and Tuesday...the transition toward more stable and dry conditions will continue Monday, as the upper low weakens and exits eastward of the state. High pressure drifting well north of the region will further strengthen the trade wind weather pattern across the islands to begin the work week. This pattern will reinforce the trend toward drier and more stable conditions across the islands. However, current trends suggest enough moisture lingering around the islands (modeled PW values 1.25 to 1.35", moisture depths 9k-13k ft) to maintain increased areal coverage of showers across windward locations into Tuesday. Showers will remain focused across mainly windward areas. However the airmass will quickly stabilize through the beginning of the week, which will greatly reduce the threat of locally heavy rainfall. Wednesday into next weekend...the airmass continues to become more dry and more stable, with forecast PW values falling to under 1.00" while modeled moisture depths fall to around 8k ft or less. This pattern will greatly reduce the intensity and areal coverage of showers across the islands. Lingering trade wind flow will maintain showers to mainly favored windward locations, with the most persistent showers at night through early morning hours. && .AVIATION... Breezy easterly trade winds will prevail through the 24-hr forecast period, with clouds and showers favoring windward areas. Shower coverage may increase overnight as an area of moisture continues westward through the area. Some showers will may be heavy at times and a thunderstorm or two can't be ruled out with the added instability associated with an upper low over the islands. With the breezy trades in place, some showers will manage to reach leeward areas. AIRMET Sierra for tempo mountain obscuration will be possible later this evening and through the second half of the overnight period as the aforementioned area of moisture moves through. AIRMET Tango for moderate low-level turbulence will continue over and downwind of island mountains. && .MARINE... A strong high pressure system passing north of the Hawaii region will continue to produce fresh to strong trade winds over the coastal waters through next week. An upper level low over the eastern islands will continue to slowly drift eastward. This low will enhance shower activity mainly over southern and eastern waters on Sunday before drifting away from the region. A Small Craft Advisory (SCA) remains in effect for all waters due to winds and seas through tonight. Winds and seas will decrease on Sunday with stronger trade winds with the SCA decreasing in coverage to the typical windier waters and channels around the islands in Maui and Hawaii Counties. More stable conditions are forecast for Sunday, though a chance for thunderstorms will linger longer over eastern waters. A medium period north-northwest to north swell (340-350 degrees) will hold into Sunday before fading. On Monday, the next long period northwest swell (310-320 degrees) will arrive and slowly fill in, peak on Tuesday and Wednesday, and then lower during the latter half of next week. On Thursday, a larger swell from the north- northwest (340 degrees) will arrive and may produce surf near advisory levels for exposed north and west facing shores. Surf along south facing shores will ease through the weekend as a long- period south swell energy fades. Surf along east facing shores will trend up through the early part of the new week as a belt of fresh to strong easterly trades develops over and far upstream of the islands. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Sunday 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 PM HST Sunday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...SWR AVIATION...Gibbs MARINE...Bohlin Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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