| Current Conditions | ||
| Temp |  | 4.1 C |
| RH | | 9 % |
| Wind | | NE 19 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 480 FXHW60 PHFO 250130 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 330 PM HST Thu Sep 24 2020 .SYNOPSIS... After a breezy couple of days, trade winds will diminish Sunday, then remain light for most of next week. An area of enhanced moisture passing through the islands will depart this afternoon. Expect a few brief windward showers over the next couple of days, with light winds keeping mostly dry weather in place Sunday into next week. && .DISCUSSION... There is no change in forecast philosophy from this morning. A surface ridge far north of the main Hawaiian Islands will maintain locally breezy trade winds into the weekend along with a few brief showers. Low pressure passing north of the ridge will push it closer to the islands beginning Sunday, causing winds across local waters to decrease. Winds will then remain light for a good portion of next week. Local land and sea breezes may form, especially over leeward areas. Satellite loop shows significantly clearer conditions across the islands versus 24 hours ago, while radar shows isolated to scattered light showers across windward and some mauka areas. Expect a rather dry trade wind weather pattern statewide through the forecast period as a stabilizing upper ridge caps deep convection and allows just a few windward showers with limited total rainfall. Light winds beginning Sunday and Monday will persist for most of next week as remnants of TS Lowell pass northeast of the islands and as troughing far north of the islands keeps the ridge weak. Decreasing flow Sunday will give way to light and variable winds by Monday, with land and sea breezes expected, especially across leeward areas. This will result in a daily weather pattern characterized by clear nights and mornings, with afternoon interior clouds possibly dropping a few showers. While this looks to be mostly a dry weather pattern, models hint at an area of moisture developing west of Lowell that could be near the islands Sunday and Monday. This could delay the drying trend for a few days if this materializes. && .AVIATION... Drier conditions will overtake the area for the next several days, though occasional light showers will continue to move through windward areas in the trade flow through tonight. A few light showers could be pushed leeward at times as well. Trades will continue locally breezy through tonight as the inversion quickly lowers to about 5000 ft, then slowly decrease into the weekend as the pressure gradient relaxes over the state. AIRMET Tango is in effect for tempo low-level turbulence over and south through west of the mountains of all islands due to the strong trades and will likely continue at least through tonight. && .MARINE... A zonal orientated surface high whose axis is centered near 35 N latitude is forecast to move eastward towards the U.S. West Coast over the next few days. This will be in response to a southeastern- advancing Northern Pacific cold front. The associated western upper ridge will slow the southern movement of the front. The boundary will reach our northern-most offshore waters Tuesday providing brief westerly winds over those waters Wednesday. Tropical Storm Lowell's remnant low will be nearing the far eastern offshore waters early next week. This weak circulation will not be of any significance as it interacts with the aforementioned cold front and dissipates. The most recent ASCAT pass showed 25 knots winds present in the Alenuihaha Channel with around 20 knot sustained winds over the channels and bays surrounding Maui County and the waters south of the Big Island. These winds are forecast to slightly strengthen overnight so the Small Craft Advisory (SCA) remains in effect until 6 AM HST Friday for those zones including the Alenuihaha Channel. With the ridge of high pressure traveling south and weakening the pressure gradient over the state, early week trades will be on the downward trend to just a gentle easterly breeze by Monday. Deep ocean buoys 51001 and 51004, northwest of Kauai and southeast of the Big Island respectively, are both recording near 6 foot swell at 12-15 second periods this afternoon. While much of this swell is not being realized along high north faces, side lobes of this energy clipping the chain have produced 4 to near 7 foot size surf along the North Shore of Oahu today. These swells will produce similar surf along north-facing shores through tomorrow (Friday) before gradually lowering this weekend. The current offshore 6 foot/10 second period south-southwest swells will be reinforced by a series of slightly longer period swells generated from large gales south of New Zealand a week ago. Spectral density plots of ample near 16 second energy across American Samoa these past two to three days will be realized along south-facing shores from Friday through Sunday. 3 to 6 foot wave heights may will approach surf advisory levels during this Friday through Sunday period. Due to the a weakening trade regime this weekend, surf along east-facing shores will be lowering to small. We may receive a small bump in easterly swell resulting in a small lift of surf early next week from the energy produced from weakening Tropical Storm Lowell. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Friday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Powell AVIATION...TS MARINE...Blood Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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