Current Conditions
Temp0.1 C
RH57 %
WindNW 16 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Tuesday 28 June (0300 UTC Wednesday 29 June) 2016
Warning(s)
Increasing humidity
Chance for fog/rain
Cloud Cover and Fog/Precipitation Forecast
Humidity is set to linger near 80%, increasing the risk for fog and light rain for tonight. Thick widespread clouds are also expected to build over the summit area, contributing to extensive cloud cover as the night progresses.
Summary of Key Meteorological Variables
Summit temperatures will be near 0.5 C this evening and 0 C tomorrow morning. Winds will be light and from the SW, with seeing near 0.8-0.9 arcseconds. Precipitable water is expected to exceed 4 mm through the night.
Discussion
Although the tradewind inversion will remain fairly well intact at or below 8 thousand feet through Friday night, an influx of mid/upper-level moisture/clouds is expected to raise summit-level humidity toward 80%, increasing the risk for fog and light precipitation for tonight. Humidity is set to drop back toward 20-40%, which should ensure dry/stable conditions prevail for the following 3 nights. However, there is a possibility that an influx of tropical moisture will lift/weaken the inversion toward 12-13 thousand feet, increasing the risk for more fog/rain for Saturday night. Some daytime clouds are possible through Friday, and could turn extensive over the weekend.

Broken to overcast thick widespread clouds are expected to build over the summit area during the next 24 hours and will likely blanket summit skies for Wednesday, Thursday and Friday night. These clouds are set to break up through Saturday, which should help open skies through that night. However, there is a possibility for summit-level clouds early Sunday morning.

Precipitable water is expected to linger near or exceed 4 mm through the next 5 nights.

A combination of upper-level turbulence, instability and/or moisture will likely contribute to poor seeing over the next 4 nights. While there is a possibility that the free atmosphere will become drier and more calm after Friday night, boundary layer turbulence may prohibit seeing from improving over the weekend.

No change since the morning forecast...The lower half of the atmosphere will remain under the control of the ridge to the north, while a rather well-defined tropical upper-tropospheric trough (TUTT) takes shape from the west coast out toward the Guam. While the former will maintain steady large-scale subsidence in the area and an intact inversion near 7-8 thousand feet through at least Friday night, the latter, and especially its associated sub-tropical jet, is expected to advect mid/upper-level clouds/moisture through the area, which could raise summit-level humidity toward 80% and increase the risk for fog/high humidity for tonight; the TUTT will hardly affect the stability of the atmosphere near the state. The air mass between 15-20 thousand feet is set to dry out, allowing humidity to return toward 20-40 mph for the following 3 nights, but thick overcast clouds will continue to pour into the area, likely blanketing skies during that time. Skies are expected to open up a bit an upper-level low to the northwest (and embedded in the TUTT), shifts northward a tad in response to an upper ridge building to the SE on Saturday. However, there is a possibility a remnant tropical wave will fill into the area, bringing low-level moisture/instability to the summit early Sunday morning. This could raise the stakes on fog/rain at the summit once again for the second half of the weekend.
WRF Astronomical Observing Quality Guidance
Cloud Cover and Precipitable Water Analyses
MK CN² Profiles
5 Day Forecast Summary (Graphical Trend)
HST Cloud Fog/Precip Temp Wind Seeing PW
Cover (%) Height (km) Probability (%) (Celcius) (Dir/MPH) (Arcseconds) (mm)
Tue Jun 28 - 8 PM70-905-940 / 100.5SSW/0-100.6-18-12
Wed Jun 29 - 2 AM80-1005-940 / 100SSW/0-100.7-1.18-12
2 PM80-1006-1020 / 55S/5-15NaN4-8
8 PM80-1006.5-100 / 01S/10-200.6-1.14-6
Thu Jun 30 - 2 AM80-1006.5-100 / 01S/10-200.6-1.14-6
2 PM80-1006.5-100 / 06SE/10-20NaN4-8
8 PM80-1006.5-100 / 02ESE/10-200.6-1.14-6
Fri Jul 01 - 2 AM80-1006.5-100 / 02E/10-200.6-14-6
2 PM80-1006-100 / 08E/15-30NaN4-8
Sat Jul 02 - 2 AM80-1006.5-100 / 04ENE/15-300.5-14-6
2 PM60-806.5-810 / 010E/15-30NaN3-6
Sun Jul 03 - 2 AM40-607-850 / 103ESE/20-350.5-1.14-8
2 PM60-804-660 / 156ESE/20-35NaN4-8
Rise and Set times for the Sun and Moon
Night (HST) Sun Set Twilight End Twilight Beg Sun Rise Moon Rise Moon Set Illumination (%) RA DEC
Tue Jun 28 - Wed Jun 29 19:15 20:29 4:22 5:36 1:30 N/A 31 1 59.9 7 43
Wed Jun 29 - Thu Jun 30 19:15 20:29 4:23 5:37 2:18 N/A 21 2 55.9 11 33
Thu Jun 30 - Fri Jul 01 19:15 20:29 4:23 5:37 3:09 N/A 12 3 53.6 14 39
Fri Jul 01 - Sat Jul 02 19:15 20:29 4:24 5:37 4:04 N/A 6 4 52.6 16 50
Sat Jul 02 - Sun Jul 03 19:15 20:29 4:24 5:38 5:01 17:48 2 5 52.2 17 54
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Wednesday 29 June 2016.
Additional Information
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