Current Conditions
Temp3.4 C
RH12 %
WindNW 7 mph
RoadOpen
Mauna Kea Observatories Forecast
3 PM HST Friday 28 November (0300 UTC Saturday 29 November) 2014
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
High clouds will continue to stream over the area through today and part of tonight thinning and breaking down in time. The summit sky should be cloud free by the second half of tonight.
Summary of Key Meteorological Variables
Summit temperature will be near 3 C this evening and 1 C tonight. Precipitable water will range between 1.5 and 2 mm. Winds will be from the WNW at 5 to 15 mph with seeing averaging 0.5-0.55 arcsec.
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 8-9 thousand feet and ensure the summit dry and stable through the next 3-4 nights. The inversion is expected to weaken and lift starting late on tuesday next week. Moisture at the summit might increase then. Daytime clouds will be minimal and short-lived throughout the beginning of the coming week but will become more estensive afterward.

High clouds will continue to stream over the summit through this afternoon and part of tonight. They are breaking down while thinnig, and will move away by early tomorrow morning, leaving clear skies behind from the second half of tonight through early Monday morning. More high clouds, followed by mid-level clouds, will start approaching the area late on Monday and through Tuesday. Cloud cover will become an issue the second half of the coming week.

Precipitable water will range between 1.5 and 2 mm tonight. It will linger close to 2 mm on Saturday night and drop down to 1 mm on Sunday night. It will increase again and range between 1.5 and 2 mm on Monday night to increase even further and possibly exceed 4 mm on Tuesday night.

Besides some high clouds during the first half of tonight, observing conditions will be in the average to good range through at least Sunday night. Seeing will worsen as turbulence aloft increases and weather conditions degrade from Monday and onward.

Not much is changed since the morning forecast... The mid/low-level ridge will continue to sit just north of the Islands and promote steady/strong large-scale subsidence in the area through the weekend. As a result the tradewind inversion will remain rather stable and well established, ensuring the summit to steer free of moisture and instability at least until Sunday night. Both minimal turbulence aloft and weak boundary layer turbulence will result in average/good observing conditions until then, possibly into Monday. By tuesday and Wednesday a mid tropospheric trough will approach the State from the West. As a result the tradewind inversion will lift and weaken, and moisture is likely to slip up the summit then, resulting in fog and, in general, poor observing conditions.
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)
Fri Nov 28 - 8 PM20-407-90 / 03.5WNW/5-150.4-0.71.75-2.25
Sat Nov 29 - 2 AM10-307-80 / 01WNW/5-150.35-0.651.5-2
2 PM10-306.5-70 / 06NW/5-15NaN2-3
8 PM0-20Clear0 / 02NW/5-150.4-0.71.75-2.25
Sun Nov 30 - 2 AM0-20Clear0 / 00NNW/10-200.35-0.651.75-2.25
2 PM0-20Clear0 / 05N/5-15NaN1-2
8 PM0-20Clear0 / 02N/5-150.4-0.70.9-1.3
Mon Dec 01 - 2 AM0-20Clear0 / 01NNW/5-150.4-0.80.8-1.2
2 PM0-20Clear0 / 07W/5-15NaN1-2
Tue Dec 02 - 2 AM10-307-80 / 02NW/10-200.4-0.81.5-2
2 PM10-306-80 / 07WNW/10-20NaN2.5-3.5
Wed Dec 03 - 2 AM20-405-70 / 02WNW/10-200.5-0.93-5
2 PM20-405-740 / 05SW/10-20NaN4-8
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
Fri Nov 28 - Sat Nov 29 17:51 18:59 5:22 6:30 N/A 0:20 49 22 26.3 -6 07
Sat Nov 29 - Sun Nov 30 17:51 18:59 5:22 6:30 N/A 1:18 60 23 20.1 -1 43
Sun Nov 30 - Mon Dec 01 17:51 18:59 5:23 6:31 N/A 2:16 71 0 13.6 2 47
Mon Dec 01 - Tue Dec 02 17:51 18:59 5:23 6:31 N/A 3:14 81 1 07.3 7 06
Tue Dec 02 - Wed Dec 03 17:51 19:00 5:24 6:32 N/A 4:12 89 2 01.6 11 01
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 1 December 2014.
Additional Information
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This message is also available at the MKWC road conditions page.
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