| Current Conditions | ||
| Temp |  | 0.9 C |
| RH | | 17 % |
| Wind | | WSW 25 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 538 FXHW60 PHFO 181338 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 338 AM HST Mon Mar 18 2019 .SYNOPSIS... Trade winds will continue to blow across the islands along with slightly cooler temperatures lasting through Tuesday. Warmer temperatures will return on Wednesday with light winds as another cold front approaches Hawaii from the northwest, briefly weakening the high pressure ridge north of the state. Breezy trade winds are forecast on Thursday and strong trade winds develop on Friday as a high pressure system builds in north of the Hawaiian Islands. Another shallow cold front moves into the northwestern islands of Kauai and Oahu from Friday night into Saturday morning with increasing clouds and showers over both islands. Clouds and showers along the frontal band will then spread southeastward down the rest of the island chain. && .DISCUSSION... Satellite imagery this morning shows an extensive stratocumulus cloud bank north of the state. Most of these clouds will decrease in coverage after sunrise due to atmospheric heating and mixing. The shallow cold front has drifted east of the Big Island. Large scale atmospheric subsidence will keep stable conditions in the forecast with only isolated showers possible along windward mountain areas through Tuesday. A surface high will migrate eastward over the next few days passing just north of the island chain with moderate northeast trade winds forecast through Tuesday. As the high moves into the East Pacific another shallow cold front will approach the islands from the north. On Wednesday, a broad trough associated with a cold front moving into the Central Pacific will weaken the high pressure ridge north of the state. These weaker pressure gradients will produce light and variable winds with some onshore sea breezes developing over the western islands. The atmosphere will remain fairly stable through the middle of the week as strong downward atmospheric motions (Subsidence) will keep cloud heights capped at around 6000 feet resulting in a dry weather pattern through Friday afternoon. Long range weather models continue to show a high pressure ridge building into the region by the end of the week. Increasing trade winds will drive a shallow cold front into the northwestern half of the state from Friday night into Saturday morning. Expect increasing clouds and some showers over Kauai and Oahu during this time period. Clouds and elevated showers along the frontal band will then spread southeastward to Maui County on Saturday, and the Big Island on Sunday morning. The American (GFS) model cross sections are showing deeper cloud heights, as compared to the previous frontal system, with cloud tops rising up to the 10,000 to 12,000 foot level. These deeper cloud heights will allow more collision of cloud droplets within the cloud layer, thereby increasing rainfall chances across the state. Strong trade winds will help lift clouds over windward mountain ranges, enhancing rainfall chances along north and east sections of all islands. Some of the stronger shower bands will likely bring at least scattered rainfall into leeward areas with the passage of this cold front. Model solutions differ a bit on the movement of this frontal band, expect some timing changes as the Friday to Saturday forecast period gets closer. We increased precipitation chances for the Friday through Sunday time period to account for the next cold frontal passage. A blended approach was used between the American (GFS) model and the European (ECMWF) models with additional weighting towards the GFS solution. Breezy to strong trades will continue through the weekend into the first half of next week as a 1030 MB surface high lingers north of the Hawaiian Islands. && .AVIATION... In the wake of a passing shallow cold front, winds have veered northeasterly at around 10-15 KT. These winds will continue to veer east northeasterly this morning and into this afternoon. Limited shallow moisture will leave the area mostly dry with the exception of ISOL -SHRA along the windward coasts and slopes. No AIRMETS are in effect and none are expected during the period. && .MARINE... Fresh to strong north-northeast winds associated with high pressure building to the north will shift out of the east tonight into Tuesday. A brief period with light and variable winds will become a possibility through the midweek time frame as the ridge shifts south over the area due to a passing front to the north. A return of fresh to strong trade winds will be possible Thursday into next weekend as high pressure builds north of the area in the wake of the passing front. Surf along north and west facing shores will hold above warning levels today, then drop to advisory levels Tuesday as the large north-northwest swell gradually eases. For more details regarding the potential impacts associated with the large surf see the latest High Surf Warning that remains in effect until 6 PM HST today. The active pattern across the northern Pacific will continue through the week with overlapping long-period northwest swells expected Wednesday, Friday, and Saturday night. These reinforcements will be similar in size, which will keep the surf around advisory levels for north and west facing shores each day. The northwest swell Wednesday and Wednesday night will be the largest of the three, which could drive the surf toward warning levels around its peak. Surf along east facing shores will remain small through midweek, then rise Friday into the weekend as strong trades return locally and upstream. Surf along south facing shores will remain small through the week with mainly background southerly pulses moving through. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Warning until 6 PM HST this evening for Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu Koolau-Molokai-Maui Windward West-Maui Central Valley-Windward Haleakala-Big Island North and East. High Surf Advisory until 6 PM HST this evening for Kona. Small Craft Advisory until 6 AM HST Tuesday for all Hawaiian waters- && $$ DISCUSSION...Bohlin AVIATION...JT MARINE...Gibbs Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
|