| Current Conditions | ||
| Temp |  | 8.6 C |
| RH | | 22 % |
| Wind | | W 13 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 192 FXHW60 PHFO 191955 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 955 AM HST Tue Oct 19 2021 .SYNOPSIS... A ridge of high pressure approaching the islands will make for gentle trades the next couple of days. A dry and stable airmass will give lots of sunshine and relatively few showers to the Aloha State. The remnants of an old front will reach Kauai Thursday, and might also spread to Oahu Thursday night or Friday, bringing an increase in clouds and some showers. Trades will start to increase Thursday and become breezy over the weekend. A dry and stable airmass will also return this weekend with fine weather expected. && .DISCUSSION... No surprises in store for this morning, with no changes to the forecast, and few changes anticipated with the afternoon package. The short term forecast remains relative dry, with weakening winds. Expect fewer showers than normal through Wednesday with the dry and stable airmass overhead. Tonight, dewpoints are expected to drop the upper 50s to lower 60s, but start to rebound tomorrow night. Few clouds and showers are over and upstream of the islands, so don't expect much in the way of cloud coverage today or tomorrow. Satellite shows the cloud band associated with a cold front north of the islands to be along 30N. It is this front that is pushing the ridge over the islands, leading to the weakening of our trade wind flow. Some areas could see land and sea breezes today, but more likely tomorrow, as the winds weaken. Even as the winds weaken, expect a background trade wind pattern. The front is expected to fall apart as it sinks south and the parent low lifts to the north. Remnants of the front will likely impact the northern islands Thursday and Friday, around the same time as an upper level trough moves over head. The frontal remnants will boost the low level moisture, and the upper level feature will help to to provide some support for the possibility of some enhancement to the showers. That all being said, overall rainfall amounts are still expected to be fairly modest. Beyond Friday, expect a new high to build in, allowing breezy trades to return with another round of drier and more stable airmass. && .AVIATION... A ridge of high pressure continues to move towards the island chain from the north today, easing trade wind speeds across the state. Shower activity will be limited to north through east sections of the islands and adjacent waters throughout the forecast period. However, even this shower activity will be mostly isolated in nature given the increasing stability overhead. Although brief periods of transient low clouds are possible, VFR flight conditions are expected to prevail throughout the next 24 hours and beyond. There are currently no AIRMETs in effect, and none are anticipated today or tonight. && .MARINE... Moderate trades will be gradually trending down to generally light to gentle breezes the next couple of days as a series of North Pacific cold fronts weaken the ridge north of the islands. These fronts will cross the north offshore waters Wednesday and Thursday and are expected to dissipate before reaching the state. High pressure will re-establish itself north of the islands by Friday and this will strengthen weekend trades back into the moderate to locally strong category. A moderate north-northwest swell will slowly fill in tonight and steadily build throughout the day Wednesday. This swell will likely peak Wednesday night and gradually decline on Thursday. A reinforcing north swell is expected to fill in Thursday night and peak on Friday. Both of these swells could get near the High Surf Advisory threshold during its peak. With the swells being out of the northerly direction, harbor surges are expected over the Kahului and Hilo harbors especially on Friday due to an increase in swell height (6 to 8 feet) and a decrease in swell period (12-13 seconds). Swell direction will also be directly out of the north (010 degrees). Surf along south facing shores should see a small increase as a new south-southwest swell fills in further this afternoon and Wednesday. Surf along east facing shores could see some wrap from the pair of northerly swells over the next several days. Otherwise, trade wind swell will be on the increase Friday into the weekend as the trades strengthen. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...M Ballard AVIATION...Vaughan MARINE...Kino Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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