| Current Conditions | ||
| Temp |  | 5.2 C |
| RH | | 16 % |
| Wind | | NE 0 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 732 FXHW60 PHFO 250207 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 407 PM HST Sat Jun 24 2017 .SYNOPSIS... A mid level trough will pass over the islands this weekend, weakening the trade winds and increasing showers across the area. The mid-level trough will shift west of the State by early next week, with high pressure then building back northeast of the islands. This will result in a drier and more stable trade wind regime, with the trades increasing into the breezy to locally windy range through much of next week. && .DISCUSSION... The 00z soundings show the capping inversion over the state has risen to about 9000 feet, with about 1.2 inches of precipitable water at both sites. However, 700 mb temperatures are still in the double digit range, warmer than originally forecast by the models, indicating that weak mid-level features are not having as much of an effect at destabilizing the airmass as originally expected. Nevertheless, a few showers have popped up over leeward areas this afternoon. Sunday looks similar to today. Leeward clearing in most areas tonight should be followed by some afternoon cloudiness and limited hit-or-miss shower activity as sea breezes and diurnally driven upslope flows take over. Windward areas will likely see more sunshine than leeward areas in the afternoon, but with the background flow still gentle trades, we can't rule out nighttime or morning showers in this hybrid pattern. Our weak trades right now are being driven by a faraway high pressure area about 1600 mi to the NNE of Hawaii. A surface ridge extending SW from this high will be pressing SE toward the islands in the coming days, tightening the pressure gradient. This will lead to a return to locally breezy trades for the eastern islands starting as early as Monday, with breezy to locally windy trades statewide by Tuesday. Drier and more stable air is expected to dominate our weather picture Tue-Thu. Models are in fairly good agreement showing a stronger mid-level feature may develop to the NE of the islands toward the end of the week, possibly enhancing incoming trade wind showers by next weekend. && .MARINE... Gentle to moderate trade winds associated with high pressure far north of the state will continue through the weekend. Fresh to strong trades are expected to return Monday and continue through the upcoming week as the pressure gradient tightens over the area. Small craft conditions are likely through this period over the typically windier channel waters, Maalaea Bay and south of the Big Island. Beginning tonight, tides and surf along south facing shores will lower Sunday into the upcoming week. However, a background southeast swell will continue into mid-week, keeping south shore surf bumped up slightly. Surf along east facing shores will build early next week due to a combination of a moderate northeast swell associated with a batch of gales off the west coast and increasing trade winds locally and east of the state. There still remains some uncertainty of the size of this swell and whether or not a high surf advisory will be needed for east facing shores next week. Regardless, rough surf seems likely for east facing shores next week. For more details on the surf, please refer to the Oahu Collaborative Surf Forecast (SRDHFO). && .AVIATION... East to east southeast trade winds will continue tonight. However, we expect development of afternoon sea breezes and cloud build ups along western and mountain sections of the islands on Sunday. Tempo showers and ceilings with isolated MVFR are possible and AIRMET Sierra may be needed later for mountain obscuration. No other AIRMETs are being considered or expected. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ R Ballard/Stall/Powell Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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