| Current Conditions | ||
| Temp |  | -0.1 C |
| RH | | 95 % |
| Wind | | E 17 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 286 FXHW60 PHFO 190630 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 830 PM HST Mon Sep 18 2017 .SYNOPSIS... High pressure to the north of the islands will keep a moderate to breezy trade wind flow in place through the remainder of the work week. The trades will ease to light and locally moderate levels over the weekend into early next week, as the high north of the State weakens. Showers will favor windward and mauka areas through the period, with a stray shower reaching leeward areas from time to time. Showers will be most prevalent during the night and morning hours. && .DISCUSSION... Currently at the surface, a 1031 mb high is centered around 1400 miles to the north-northeast of Honolulu, and is driving the breezy trade winds across the island chain this evening. Infrared satellite imagery shows partly cloudy skies in most areas, with a few patches of enhanced cloud cover riding into windward areas with the trades. Meanwhile, radar imagery shows scattered windward showers with a stray shower drifting leeward from time to time. Main short term concerns revolve around trends in the trade wind speeds and rain chances. Tonight through Friday, High pressure to the north-northeast of the island chain will maintain a moderate to breezy trade wind flow through the remainder of the work week, but we should see a gradual decrease in the trade winds speeds as the weak progresses. Bands of clouds and showers will continue to drift through the island chain, with the showers focusing primarily over windward and mauka areas during the night and morning hours. A stray shower may also drift into leeward areas from time to time due to the strength of the trades. Friday night through next Monday, High pressure will weaken and shift eastward well to the northeast of the State over the weekend into early next week, as a cold front tracks eastward across the central Pacific well north of the island chain. This will likely result in a decrease in the trade wind speeds across the area, with generally light to locally moderate trades expected. Additionally, some localized land and sea breezes may become more prominent in the more sheltered areas. A windward/mauka favored shower pattern is expected to continue through the period, although we may see an increase in leeward and interior shower development during the afternoon and evening due to the easing of the trades and an upper level trough in the vicinity of the islands. && .AVIATION... Strong high pressure fare N of the islands will support breezy trade winds. AIRMET Tango will remain in effect through 24 hours and beyond. Ragged clouds and showers, carried in by trade winds, will favor the windward slopes and coasts of all islands. Partly cloudy skies are expected overnight across leeward areas. Inland showers are expected to redevelop Tuesday Afternoon across leeward Big Island. Brief MVFR conditions possible in showers statewide, otherwise VFR conditions will prevail all areas. && .MARINE... Strong high pressure far NNE of the islands will support fresh to strong trade winds as it remains nearly stationary through Wednesday. The high will gradually diminish late in the week and over the weekend, with the associated ridge being shunted toward the islands as a front approaches from the NW. This will lead to a gradual decrease in trade wind speeds, especially over the weekend, potentially continuing into early next week. A Small Craft Advisory (SCA) will gradually be pared back in area as winds diminish, but will likely be necessary for the windiest zones through at least Thursday. The nearby and upstream fetch of elevated trade winds will support choppy short-period surf along E facing shores as wind waves come ashore. Otherwise, the only significant swell source is a low to the NW that will send a 3-4' WNW swell toward the islands that will likely arrive Thursday and peak on Friday. See the latest Oahu Surf Discussion (SRDHFO) for additional details. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. Small Craft Advisory until 6 AM HST Tuesday for Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters. && $$ DISCUSSION...Jelsema AVIATION...Bedal MARINE...Birchard Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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