Current Conditions
Temp4.8 C
RH6 %
WindNNW 9 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Thursday 28 August (0300 UTC Friday 29 August) 2014
Warning(s)
None
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 7 C this evening and 6.5 C tomorrow morning. Winds will be from the NW at 5-15 mph, with seeing around 0.4-0.5 arcseconds. Precipitable water is expected to be in the 1-1.5 mm range through the night.
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 9 thousand feet and ensure the summit remains dry and stable through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Summit skies will remain predominately clear through the next 5 nights.

Precipitable water is expected to linger primarily in the 1-1.5 mm range throughout the forecast period. There is a possibility that it will dip just below 1 mm, mainly late Saturday night.

Clear, calm skies will prevail at and above the summit, which will likely allow for better than average to good seeing probably through the next 5 nights. There is a possibility for excellent seeing particularly for Friday and Saturday night.

No change since the morning forecast...The mid/low-level ridge will continue to sit to the north of the Islands, while an upper-level ridge lingers over or just south of the Big Island through the long weekend. This will allow very strong/steady large-scale subsidence to prevail in the area, which will help maintain a well-defined tradewind inversion at or below 9 thousand feet and ensure a dry/stable and clear summit air mass through the next 5 nights. The extra subsidence provided by the upper-level ridge will push PW toward 1 mm and significantly warm the summit temperatures during this time. The deep subsidence should also keep shear/turbulence in the free atmosphere to a minimum and allow for good/excellent seeing throughout the forecast period. There is a possibility that seeing will dip toward 0.3 arcseconds, particularly as the upper-level ridge settles in overhead between midnight Friday and early Sunday evening.
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)
Thu Aug 28 - 8 PM0-5Clear0 / 07NNW/5-150.4-0.51-1.5
Fri Aug 29 - 2 AM0-5Clear0 / 06.5NNW/5-150.4-0.51-1.5
2 PM0-20Clear0 / 011WNW/5-15NaN1-2
8 PM0-5Clear0 / 07NNW/5-150.35-0.451-1.5
Sat Aug 30 - 2 AM0-5Clear0 / 07N/5-150.3-0.41.25-1.75
2 PM0-20Clear0 / 012N/0-10NaN1-2
8 PM0-5Clear0 / 07.5NNW/0-100.3-0.41-1.5
Sun Aug 31 - 2 AM0-5Clear0 / 07N/0-100.3-0.40.8-1.2
2 PM0-20Clear0 / 012NE/0-10NaN1-2
Mon Sep 01 - 2 AM0-5Clear0 / 06NNE/0-100.3-0.51-1.5
2 PM0-20Clear0 / 011ENE/0-10NaN1-2
Tue Sep 02 - 2 AM0-5Clear0 / 05.5ENE/5-150.35-0.550.8-1.2
2 PM0-20Clear0 / 010NE/5-15NaN1-2
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
Thu Aug 28 - Fri Aug 29 18:49 19:55 4:51 5:57 N/A 20:52 13 13 04.6 -7 31
Fri Aug 29 - Sat Aug 30 18:48 19:54 4:51 5:57 N/A 21:32 20 13 52.3 -10 59
Sat Aug 30 - Sun Aug 31 18:47 19:53 4:51 5:57 N/A 22:14 28 14 42.0 -14 03
Sun Aug 31 - Mon Sep 01 18:47 19:52 4:52 5:57 N/A 23:00 38 15 34.2 -16 33
Mon Sep 01 - Tue Sep 02 18:46 19:51 4:52 5:58 N/A 23:50 49 16 29.0 -18 16
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 29 August 2014.
Additional Information
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This message is also available at the MKWC road conditions page.
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