Current Conditions
Temp2.8 C
RH7 %
WindNNW 32 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Wednesday 10 February (0300 UTC Thursday 11 February) 2016
Warning(s)
Moderate/strong winds
Cloud Cover and Fog/Precipitation Forecast
The summit will remain clear, dry and stable through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1 C, with winds from the WNW at 25-40 mph for this evening and 30-45 mph for the morning hours. Seeing will exceed 1 arcsecond, while precipitable water is expected to be in the 0.7-0.9 mm range for the night.
Discussion
A well-defined tradewind inversion will continue to cap low-level moisture at or below 7 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Skies will remain predominately clear through the next 5 nights.

Precipitable water is expected to slip toward 0.8 mm for the next 2 nights, then settle in near 0.65-0.7 mm for the remainder of the week.

Boundary layer turbulence will contribute to bad seeing for tonight and probably poorer than average seeing for the opening half of tomorrow night. This source of turbulence is slated to rapidly subside during the latter period, allowing seeing to settle in near 0.45-0.5 arcseconds likely for the remainder of the forecast period.

No change since the morning forecast....A mature trough/low to the north of the state will continue to supress the ridge to the south of the Big Island before shifting off toward the NE and weakening, allowing a new ridge to fill in from the west later tomorrow morning. Regardless, the ridge will remain close enough to promote steady large-scale subsidence in the area, which will easily maintain a well-defined tradewind inversion near 7 thousand feet and ensure a dry and stable air mass through the week. Unfortunately, a tight wind gradient between the low and the ridge is expected to keep winds near 35-40 mph, which will stir up boundary layer turbulence and contribute bad seeing for tonight. Winds are slated to subside as the trough lifts off toward NE, likely allowing light winds to set in for the weekend, if not sooner. In addition, deep subsidence embedded in the ridge will keep turbulence in the free atmosphere to a minimum, which will help improve seeing toward 0.45-0.5 arcseconds during that time. There is also a very good chance that PW will benefit from the strong subsidence and settle in near 0.65-0.7 mm over 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)
Wed Feb 10 - 8 PM0-5Clear0 / 01WNW/25-400.8-1.60.7-0.9
Thu Feb 11 - 2 AM0-5Clear0 / 01WNW/30-451-20.7-0.9
2 PM0-20Clear0 / 08.5NNW/20-35NaN0.8-1.2
8 PM0-5Clear0 / 04.5NNW/15-300.5-0.80.7-0.9
Fri Feb 12 - 2 AM0-5Clear0 / 04.5NNW/10-200.4-0.60.7-0.9
2 PM0-20Clear0 / 09.5NE/5-15NaN0.6-1
8 PM0-5Clear0 / 05ENE/5-150.4-0.50.6-0.8
Sat Feb 13 - 2 AM0-5Clear0 / 05ENE/5-150.4-0.50.55-0.75
2 PM0-20Clear0 / 09ESE/5-15NaN0.6-1
Sun Feb 14 - 2 AM0-5Clear0 / 04.5ESE/5-150.35-0.550.5-0.8
2 PM0-20Clear0 / 09.5SE/10-20NaN0.6-1
Mon Feb 15 - 2 AM0-5Clear0 / 04SSE/5-150.4-0.60.5-0.8
2 PM0-20Clear0 / 08N/5-15NaN0.6-1
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
Wed Feb 10 - Thu Feb 11 18:28 19:33 5:39 6:44 N/A 20:59 10 23 58.7 -0 59
Thu Feb 11 - Fri Feb 12 18:28 19:34 5:38 6:44 N/A 22:00 18 0 53.8 3 32
Fri Feb 12 - Sat Feb 13 18:29 19:34 5:38 6:43 N/A 23:01 28 1 49.0 7 48
Sat Feb 13 - Sun Feb 14 18:29 19:35 5:37 6:42 N/A 0:01 39 2 44.7 11 35
Sun Feb 14 - Mon Feb 15 18:30 19:35 5:37 6:42 N/A 1:00 50 3 41.0 14 38
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Thursday 11 February 2016.
Additional Information
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This message is also available at the MKWC road conditions page.
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