| Current Conditions | ||
| Temp |  | -1.6 C |
| RH | | 16 % |
| Wind | | NNW 14 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 418 FXHW60 PHFO 231402 CCA AFDHFO Area Forecast Discussion...CORRECTED National Weather Service Honolulu HI 400 AM HST Wed Jan 23 2019 .SYNOPSIS... Fair weather will prevail through Thursday as a ridge remains in the island vicinity. Showers carried by the east to southeasterly wind flow will reach the windward areas at times. Afternoon clouds and a few showers will develop over the islands under daytime sea breezes, with partial clearing at night under land breezes. A front will move down the island chain Friday into Saturday, bringing a period of rainfall and ushering in cool northeast winds for the weekend. && .DISCUSSION... Fair weather prevails across the state early this morning, with only a few showers reaching windward Big Island. A surface high pressure ridge remains north enough to allow easterly trade winds over the eastern islands, then becoming weaker southeast winds over the western islands. An upper level ridge overhead is maintaining marginally stable atmospheric conditions, with a rather dry airmass prevailing across the area. Early morning Lihue and Hilo soundings are quite similar to Tuesday afternoon's, though there is a more pronounced trade wind inversion signature on the Hilo sounding profile, with low level moisture extending to about 7 thousand feet. The land and sea breeze weather regime that has been around the area for a while will persist through Thursday. Clouds and some showers will develop during the afternoon over the islands, followed by mostly clear conditions overnight through the early morning hours. Easterly trade winds will bring some clouds and showers mainly to windward Big Island and east Maui. Rainfall amounts will be limited. Change in the weather is expected by Friday, as a front will move down the island chain Friday into Saturday. Latest forecast solutions are still in fairly good agreement, showing clouds and showers along the front reaching Kauai Friday afternoon, then advancing down the island chain and reaching the Big Island late Friday night or Saturday morning. Expect rainfall to favor north facing terrain and windward slopes, though rest of the areas may see some precipitation as well. Much of the upper level support for this frontal system will stay to the northeast of the state, hence the probability of heavy rainfall along the frontal band will be low. Breezy northerly winds will likely develop behind the front, ushering in a cool airmass with dew points in the mid to upper 50s. Showers will favor windward slopes, and even reaching the lee portions of the smaller islands. This cool winter weather should hold through Monday. && .AVIATION... VFR conditions will prevail as a surface ridge of high pressure remains just north of the islands in a stable atmosphere. Light winds will allow land and sea breezes to develop and modify wind directions with some interior and mountain clouds over each island during the afternoons. No AIRMETs in effect and none expected. && .MARINE... A ridge will remain just north of Kauai through Thursday putting the island chain in a light to locally moderate east to southeast wind flow. A cold front will move through the islands Friday and Saturday, ushering a brief period of moderate to locally strong northeast winds. The west-northwest swell came alive in the past couple of hours as buoy 51001 topped 13.8 feet, 16 to 17 seconds. Buoy 51101 was slightly smaller at 11 feet. With this data, the swell is up to three feet above WAVEWATCH III guidance. We also bumped up the High Surf Advisory to a warning for the north and west shores of Kauai and Niihau. With this swell coming in at 300 to 310 degrees, the swell will be blocked downwind, thus slightly smaller surf for the islands east of Kauai and Niihau. But it will still be advisory for these island's west and or north shores. The warning and advisory are in effect through 6 pm HST Thursday. Advisory level surf will also reach the leeward shores of the Big Island later today, lasting through Thursday. Another west-northwest swell, but slightly smaller in size, is due in Thursday night, peak Friday, followed by a slow but gradual decline through the weekend. This swell, which tend favor advisory level surf, will prolong the High Surf Advisory through Saturday. No new northwest swell is expected over the weekend, but a moderate west-northwest swell, from 300 to 310 degrees, reaches our north and west facing shores Sunday night. It will max out at 7 feet and 16 seconds on Monday. This translate to surf heights near advisory level of 15 feet along the north facing shores. A Small Craft Advisory (SCA) for seas, is in effect through Thursday afternoon for near-shore waters exposed to both northwest swells. The SCA, which is set to expire at 6 pm HST Thursday, could be extended through at least Friday. We will see how big the next northwest is before making this determination. A slightly elevated east swell, generated by a pocket of moderate to strong trade winds upwind of the islands several days ago, has arrived. The swell is expected to peak today and hold through tonight, followed by a slow decline through Friday. The surf may bump up to near advisory level for east facing shores at its highest. Some south facing shores, exposed to this swell, may see bigger surf as well. Otherwise, surf along south facing shores will be small throughout the period. WAVEWATCH III is suggesting a small north-northeast swell late in the weekend, followed by a building north swell Monday, peaking Tuesday night at 6 feet 12 seconds. This may bring advisory to the east facing shores with a northern exposure. The source of this swell is from a forecast gale low some 950 nm north of the islands over the upcoming weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Warning until 6 PM HST Thursday for north and west facing shores of Kauai and Niihau. High Surf Advisory until 6 PM HST Thursday for north and west facing shores of Oahu and Molokai, north facing shores of Maui and west facing showers of the Big Island. Small Craft Advisory until 6 PM HST Thursday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel- Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters- Alenuihaha Channel-Big Island Windward Waters. && $$ DISCUSSION...Hui AVIATION...Bohlin MARINE...Lau Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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