| Current Conditions | ||
| Temp |  | 6.4 C |
| RH | | 4 % |
| Wind | | NE 6 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 278 FXHW60 PHFO 250651 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 850 PM HST Sun May 24 2020 .SYNOPSIS... Lighter winds and mostly dry weather are expected through Tuesday, with a few showers possible, mainly during the afternoon and evenings. Trade winds are expected to strengthen Wednesday, and remain in place into next weekend, delivering a few brief showers to windward areas. && .DISCUSSION... Currently, light to moderate E-SE winds prevail on the large scale, lighter near Kauai as compared to the Big Island, due to a surface ridge located a couple hundred miles N of Kauai. The low-level flow is mostly dry, except upstream of the Big Island, where a few showers are riding in on the trades, although high clouds are somewhat hiding them from being seen in latest infrared satellite images. The island atmosphere is stable, with a nearby mid- and upper-level ridge supporting a strong subsidence inversion. Clear and mostly dry conditions will prevail through tomorrow morning, except for some showers near Kona this evening, and a few brief showers over windward Big Island later tonight. While little overall change to the weather pattern is expected over the next couple of days, a subtle decrease in wind speed is anticipated as the ridge is pushed a little closer to Kauai by a rapidly strengthening low passing far N of the area. So while the trade wind flow may have been a little stronger than expected today, thereby preventing significant leeward sea breezes/clouds, we may see a few more afternoon leeward clouds Monday and Tuesday as winds diminish. Leeward clouds or not, significant rainfall is not expected as the island atmosphere will remain stable and mostly dry. Nights and mornings will be mostly dry. A new high building N of the area will bring increasing trade winds Wednesday/Thursday that will persist into next weekend, delivering what is expected to be only brief windward showers. Leeward Big Island will see afternoon clouds and showers, that will linger through the evening hours, and sometimes into the early morning. Worth noting that while most of the state is entering the dry season, it is the wet season for leeward Big Island. Interestingly 1.68" of rain has been recorded at PHKO in the last 24 hours, mostly due to a soaking heavy shower around 3 am last night. High clouds near the Big Island are expected to spread over the other islands beginning Monday night, potentially persisting for several days. If guidance continues this trend, sky cover will be increased in the forecast. && .AVIATION... A strong ridge of high pressure to the north of the islands will maintain light easterly flow across the state. Light sea breezes will predominate most areas in the afternoon and early evening hours while weak land breezes will be the rule in the late night and morning hours. The air mass over the state remains mostly dry and mostly stable. Shower activity will be limited and will occur mainly over island interiors during the afternoon and evening hours. Isolated MVFR CIG and VIS are possible in brief showers. Otherwise, VFR conditions will prevail all areas. No AIRMETs are in effect or anticipated at this time. && .MARINE... A surface ridge about 270 nm north of Kauai will continue to drift slowly toward the south during the next couple of days. This will maintain moderate easterly trade winds around the Big Island and Maui, with weaker east-southeast background flow from Molokai to Kauai. Stronger high pressure is forecast to develop far north of the state Wednesday, which will cause the easterly trade winds to strengthen from mid-week through Friday. There are no Small Craft Advisory conditions in the current forecast this week. South facing shores will see periods of surf around the May average through much of the week. A longer period south-southwest swell will likely combine with a small south-southeast swell to produce moderate sized surf near or just below the May average through the Memorial Day Holiday, followed by a slight drop on Tuesday and Wednesday. Another pulse of south-southwest swell energy is expected from late Thursday through Saturday. Small north-northwest swells are expected to produce surf near the May average along most north facing shores of the smaller islands through mid-week. The small northwest swell will eventually shift out of the north from Thursday night through Saturday. Surf along east facing shores will likely remain below the May average this week due to the weaker than normal trade winds in the vicinity of, as well as upstream of the state. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Birchard AVIATION...Bedal MARINE...Houston Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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