| Current Conditions | ||
| Temp |  | 5.5 C |
| RH | | 61 % |
| Wind | | NE 7 mph |
| Road | | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 117 FXHW60 PHFO 170202 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 402 PM HST Mon Sep 16 2019 .SYNOPSIS... A return of drier air and more stable conditions is anticipated from east to west Tuesday through Thursday. Increasing moisture and rain chances will become a possibility once again over the upcoming weekend. && .DISCUSSION... At the surface, a 1025 mb high is centered about 1400 miles north of Hawaii. A passing trough and front to the northwest between the islands and the high is allowing for the otherwise moderate to fresh trade winds to veer east southeasterly across the smaller islands this afternoon. Water vapor imagery shows an mid to upper low centered about 600 miles north northwest of Kauai and moving away from the area. Southwest winds along the southeastern flank of the low is currently drawing scattered to broken mid and high level clouds across the state as shown on visible satellite. A few low clouds are anchoring along the windward slopes as well. MIMIC Total Precipitable Water (PW) shows a swath of PW near 2 inches across the central portions of the state, but 00Z soundings indicate values at 1.5 to 1.7 inches at Hilo and Lihue. The mid and high level clouds kept showers from popping up like yesterday, but there's still a small chance for leeward/interior showers into early this evening. Drier and more stable air should begin to funnel in with the upstream trades tonight. Over the next couple of days, we will be watching for development of a tropical disturbance southwest of Hawaii. Both GFS and ECMWF show a low forming and immediately moving north as an upper low far to our northwest digs southward. While neither model shows an impact to the main Hawaiian Islands, the synoptic setup may keep us in a similar east southeast flow pattern through the next several days, but will depend on how this system develops. Upstream of Hawaii, drier and more stable air will funnel in so clouds and showers should be kept to a minimum. Despite some differences between the various model solutions, a return of light winds and increasing moisture (two inch PWs) will be possible Friday night into next weekend as a trough associated with a tropical disturbance to the south moves through. Added instability associated with an upper low setting up over the state combined with this moisture will support increasing rainfall chances. && .AVIATION... High clouds continue to stream up over the state from the southwest, especially over Oahu this afternoon. Despite the elevated moisture, shower activity has been more scarce than anticipated much of the day. Some scattered showers can still be expected for the rest of the day and into tonight. Winds continue to have more of a east-southeasterly component to them, but should turn back towards a more typical trade direction through tomorrow. A drying trend with increasing trade wind speeds is on tap as we head into Tuesday thanks to the upper low north of Kauai moving away from the state. AIRMET Zulu remains in effect for light icing 160-FL280. && .MARINE... High pressure far north of the state is expected to drive moderate trade winds across the area as it slowly moves east through the week. An ASCAT pass from late this morning shows winds have dropped below advisory threshold and we have allowed the Small Craft Advisory (SCA) to expire this afternoon. However, winds near advisory threshold are expected into Tuesday. A series of small swells from the southwest, south, and southeast is expected this week. The largest of these swells looks to be towards the end of the week as a combination of a long-period south-southwest swell and potential short-period southwest swell moves in across the area. Surf heights are expected to be below advisory levels with these swells. Small surf is expected along north, east and west facing shores through the new week. Expect a small east swell from Tropical Cyclone Kiko as early as Wednesday along exposed east facing shores and likely continuing through the weekend. Exposed west shores may see some of the aforementioned southwest swell on Friday. A small northwest swell will be possible late in the weekend into early next week. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Foster AVIATION...Dye MARINE...Powell Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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