Current Conditions
Temp5.1 C
RH9 %
WindNW 15 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Wednesday 27 August (0300 UTC Thursday 28 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 5 C, with winds from the NW at 5-15 mph and seeing around 0.4-0.5 arcseconds. Precipitable water is expected to be in the 2-2.5 mm range for the first half of the night and 1.5-2 mm range for the second half.
Discussion
The tradewind inversion will continue to cap low-level moisture near 7-8 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 start out near 2.5 mm for this evening, but will drop toward 1.5 mm as the night progresses and settle in near 1.75 mm for the next 3 nights. There is a possibility that it will increase back toward 2 mm on Sunday night.

Clear, calm skies will prevail at and above the summit, which will likely allow for better than average/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 overhead probably through most of the long weekend. This will allow very strong and steady large-scale subsidence to prevail in the area, which will help maintain a well-defined tradewind inversion near 7-8 thousand feet and ensure a clear, dry and stable air mass through the next 5 nights. Winds at and above the summit will also remain relatively weak, minimizing turbulence and especially shear in the free atmosphere, which should allow for at least better than average seeing during these nights. There is a possibility for periods of excellent seeing, particularly as the center of the upper-level ridge drifts overhead mainly on Saturday. Unfortunately, minor mid/upper-level moisture is expected to linger in the area and keep PW near 1.5-2 mm probably throughout most of the forecast period.
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 Aug 27 - 8 PM0-5Clear0 / 05NW/5-150.4-0.52-2.5
Thu Aug 28 - 2 AM0-5Clear0 / 05NW/5-150.4-0.51.5-2
2 PM0-20Clear0 / 011WNW/5-15NaN1-2
8 PM0-5Clear0 / 06NW/5-150.4-0.51.25-1.75
Fri Aug 29 - 2 AM0-5Clear0 / 05.5NW/5-150.35-0.451.5-2
2 PM0-20Clear0 / 011NNW/5-15NaN1.5-2.5
8 PM0-5Clear0 / 07NNW/5-150.35-0.451.5-2
Sat Aug 30 - 2 AM0-5Clear0 / 06.5NNW/5-150.3-0.41.5-2
2 PM0-20Clear0 / 011N/5-15NaN1.5-2.5
Sun Aug 31 - 2 AM0-5Clear0 / 06N/5-150.3-0.51.5-2
2 PM0-20Clear0 / 011NNE/5-15NaN1.5-2.5
Mon Sep 01 - 2 AM0-5Clear0 / 05.5NNE/0-100.4-0.61.5-2.5
2 PM0-20Clear0 / 010.5NE/5-15NaN1.5-2.5
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 Aug 27 - Thu Aug 28 18:50 19:56 4:50 5:57 N/A 20:14 7 12 18.5 -3 48
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
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Thursday 28 August 2014.
Additional Information
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This message is also available at the MKWC road conditions page.
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