Current Conditions
Temp5.8 C
RH28 %
WindWNW 10 mph
RoadOpen
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Wednesday 28 January 2015
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 6 C this afternoon, 1 this evening and 0 C tomorrow morning. Winds will be from the WSW at 10-20 mph, with seeing around 0.5-0.6 arcseconds. Precipitable water is expected to be in the 1.25-1.75 mm range for 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 through Friday, but could pick up a tad over the weekend.

Skies will remain clear through the next 5 nights.

Precipitable water will linger near 1.5 mm for tonight, increase to 2-3 mm for Thursday and Friday night and probably 3-4 mm over the weekend.

Light/moderate turbulence in the lower part of the atmosphere may only allow for average-like seeing. Steady boundary layer turbulence is expected to contribute to poor seeing for the remainder of the week.

The mid/low-level ridge will continue to sit over/near the Islands and promote steady/strong large-scale subsidence in the area through the week. This will help maintain a well-defined tradewind inversion at or below 9 thousand feet and ensure the summit remains dry and stable throughout the forecast period. Skies will also remain predominately clear with a zonal westerly jet persisting to the north of the state into the early part of next week. However, there is a possibility for light/moderate turbulence in the lower half ot the atmosphere, which may only allow for average-like seeing for tonight. A building very large trough to the north of the state will hardly affect the stability of the atmosphere or affect the orientation of the jet, but could increase summit-level winds and inject minor mid-level moisture to the area for the remainder of the week. The former will increase boundary layer turbulence and contribute to poor seeing, while the latter will help push PW toward 2-3+ mm after tonight. There is also a chance that another trough will fill in from the northwest, further strengthening summit-level winds and perhaps bring instability and significantly more moisture to the area around the middle part of next week. This could result in another round of poor/bad perhaps even inoperable summit-level conditions around Tuesday/Wednesday.
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 Jan 28 - 2 PM0-20Clear0 / 06WSW/10-20NaN1.25-1.75
8 PM0-5Clear0 / 01WSW/10-200.5-0.61.25-1.75
Thu Jan 29 - 2 AM0-5Clear0 / 00SW/10-200.5-0.61.25-1.75
2 PM0-20Clear0 / 05.5SW/15-30NaN1.25-1.75
8 PM0-5Clear0 / 00.5WSW/15-300.6-12-3
Fri Jan 30 - 2 AM0-5Clear0 / 00WSW/20-350.6-12-3
2 PM0-20Clear0 / 05WSW/20-35NaN2-3
8 PM0-5Clear0 / 00WSW/15-300.7-1.12-3
Sat Jan 31 - 2 AM0-5Clear0 / 0-0.5WSW/20-350.7-1.12-3
2 PM0-20Clear0 / 04.5WSW/20-35NaN2.5-3.5
Sun Feb 01 - 2 AM0-5Clear0 / 0-1W/15-300.6-13-4
2 PM0-20Clear0 / 04W/15-30NaN3-5
Mon Feb 02 - 2 AM0-5Clear0 / 0-0.5W/15-300.6-13-5
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 Jan 28 - Thu Jan 29 18:21 19:28 5:42 6:49 N/A 2:49 72 4 16.9 17 08
Thu Jan 29 - Fri Jan 30 18:22 19:28 5:42 6:48 N/A 3:42 81 5 10.8 18 14
Fri Jan 30 - Sat Jan 31 18:22 19:29 5:42 6:48 N/A 4:33 88 6 04.2 18 23
Sat Jan 31 - Sun Feb 01 18:23 19:29 5:42 6:48 N/A 5:20 94 6 56.7 17 38
Sun Feb 01 - Mon Feb 02 18:23 19:30 5:41 6:48 16:33 6:05 98 7 48.0 16 02
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Wednesday 28 January (0300 UTC Thursday 29 January) 2015.
Additional Information
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This message is also available at the MKWC road conditions page.
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