| Current Conditions | ||
| Temp |  | 1.3 C |
| RH | | 12 % |
| Wind | | SW 13 mph |
| Road | | Open (4x4) |
|
Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans: |
|
Narrow the Menu List Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special |
|
|
Hawaiian Islands Synoptic Discussion and Guidance 303 FXHW60 PHFO 260639 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 839 PM HST Wed Apr 25 2018 .SYNOPSIS... Trade winds will begin to decrease late tonight through Thursday night as high pressure to our north weakens. Low level flow will shift to southeasterlies late Thursday and Thursday night as a front approaches from the northwest. This front will bring increased rainfall to the islands, with showers reaching Kauai Thursday night and Friday, before moving down the island chain Friday night through Sunday morning. Showers may linger into the new work week over the Big Island. && .DISCUSSION... A 1031 mb high far north of the main Hawaiian Islands continues to drive moderate to locally breezy trade winds across the chain this evening. Satellite loop shows a band of broken to overcast low clouds embedded within trade flow approaching the islands from the east, but skies are generally partly cloudy to clear across most areas of the islands at this hour. Trade showers will likely pick up tonight as the cloud band arrives. Rainfall will continue to favor windward and mauka areas. Models show trade winds will begin to decrease late tonight through Thursday night as the high to our north weakens and gets pushed eastward by a front expected to develop to our northwest. Local winds will begin to change from weak northeasterly trades to southeasterlies as this front approaches the islands late Thursday and Thursday night. The front will reach Kauai early Friday, spreading increased showers along and ahead of it. Uncertainty remains concerning the strength of the front as it moves across the islands Friday into Sunday. Models show colder temperatures aloft developing by Sunday, likely making this front a more prolific rain producer as it reaches the Big island late in the weekend. The probability for heavy rainfall increases from Friday through Sunday, but it remains too early to tell which island, if any, is under threat. The frontal boundary may stall near the Big island, possibly providing that islands with lots of rainfall into early next week. We expect drier trade wind flow will return to the smaller islands after frontal passage, setting up a pattern of windward and mauka showers, post-frontally, into next week. Moisture from the frontal boundary near the Big island may enhance these showers from time to time. && .AVIATION... Moderate strength trade winds will begin to weaken on Thursday as a trough approaches the islands from the northwest. AIRMET Tango remains in effect overnight for Tempo Moderate Turbulence over and downwind of mountain areas. This low level turbulence AIRMET will likely be removed by Thursday morning as trade wind speeds decrease. A band of unstable clouds just east of the Big Island will drift slowly across the state producing periods of MVFR ceilings and showers mainly along windward slopes of all islands through Thursday morning. A few of these showers will drift leeward, however mostly VFR conditions are forecast along southern and western slopes of each island. && .MARINE... A surface high far to the NNE will move E and gradually weaken over the next two days as a low develops about 1000 miles N of the islands. Fresh to locally strong trade winds will weaken Thursday, then collapse completely Thursday night as a weak trough develops over the area. A Small Craft Advisory (SCA) currently posted for the windier marine zones around Maui and the Big Island will likely be allowed to expire Thursday morning as the high weakens and trade winds begin to diminish. A front associated with the developing low is expected to reach Kauai sometime Friday, then move down the chain through Saturday before potentially stalling near the Big Island through the rest of the weekend. Initially, right behind the front, N winds may briefly reach SCA criteria in some of the marine zones. The low will send a mix of swells and seas toward the islands this weekend into next week, with associated seas rising above 10 feet in most zones, necessitating a SCA from late Saturday into Monday. A moderate long-period NNW swell is expected to arrive tomorrow and peak Friday, with peak surf heights below advisory levels. The low that develops N of the islands late in the week will remain in place until early next week. The amount of swell/surf that arrives in the islands is somewhat uncertain, and will depend on the evolution of the low and associated fetch. Current indications are that a fairly significant (but poorly organized) swell will produce advisory-level surf along exposed N and W facing shores, with the peak of the swell around Sunday. Elsewhere, several pulses of relatively small SW to S swell are expected over the next week or so, with a peak in swell energy around Sunday. Rough and choppy surf along E facing shores will diminish Thursday and Friday. The Oahu Surf Discussion (SRDHFO) contains further details on the sources of the swells. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Powell AVIATION...Bohlin MARINE...Morrison Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
|