Current Conditions
Temp8.6 C
RH35 %
WindW 7 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Friday 26 November (0300 UTC Saturday 27 November) 2021
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for periods of fog, high humidity and ice through the night; precipitation is not expected but broken high level clouds will stream overhead moving from the southwest to northeast.
Summary of Key Meteorological Variables
Summit temperatures will be near 1.5 C this evening and 0.5 C tonight. Winds will be in the 5 to 15 mph range from the SSW through the night. Seeing will be near 0.6-0.7 arcseconds, while PW is expected to be near 2 mm for the night.
Discussion
The atmosphere is drying and stabilizing with a relatively strong inversion at about 6-7 thousand feet. Nevertheless pocket of moisture lingering in the area could result in local increase of moisture/ice/fog at times. The summit will steer free of fog and precipitation over the weekend but from Monday and through the rest of this forecast period, the atmosphere is projected to destabilize again and moisture will become an issue particularly on Tuesday.

Broken high level clouds will strem overhead from the southwest, shifting northeastward, disturbing observations tonight. These clouds will begin to breakdown and shift eastward through tomorrow morning, leaving mostly clear skies for Saturday and Sunday night. Mid level clouds approaching from the east will become an issue instead on Monday and Tuesday and are likely to cover all of the summit skies but the end of this forecast period.

Precipitable water will linger close to 2 mm tonight and range between 1.5 and 2 mm range on Saturday night. It si projected to drop to 1 mm on Sunday night. It will increase and quickly reach the 4 mm threshold by Monday and through Tuesday.

There is a brief chance for some improvement in seeing with conditions for tonight and early Saturday evening, but an abrupt increase in winds/boundary layer turbulence due to increased surface winds will drastically degrade seeing as the weekend progresses. Worsening atmospheric condition will cause further degradation through the beginning of the coming week.

No changes to the morning forecast if not for PW adjustments for tonight... The southwest flow along the trailing end of the upper level trough, currently moving eastward, will continue to advect high clouds over the area through today and part of tonight. There is a very good chance that conditions/skies will improve as the trough exits eastward by sunrise Saturday. However, a deep ridge filling in from the west, in the wake of the departing trough, will push a tight wind gradient over the summit area beginning early Sunday morning. This will result in an abrupt increase in surface winds and boundary layer turbulence, which will drastically degrade seeing starting on Sunday night. Meanwhile the moving upper level trough is projected to develop into an upper level low, which will station east of the islands and is expected to destabilize some the atmosphere from Monday and through the end of this forecast period, while pushing over mid level clouds and allowing temperature to drop below freezing for long periods of time.
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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Fri Nov 26 - 8 PM30-507-920 / 01.5SSE/5-150.4-0.71.5-2.5
Sat Nov 27 - 2 AM30-507-90 / 00.50SSW/5-150.5-0.81.5-2.5
2 PM20-407-80 / 06.5SSW/10-20NaN2.5-3.5
8 PM10-306-70 / 01WSW/5-150.4-0.81.5-2.5
Sun Nov 28 - 2 AM20-407-80 / 00.5W/10-200.45-0.851.5-2
2 PM0-207-90 / 04NNE/20-30NaN1.5-2.5
8 PM0-20Clear0 / 0-1NNE/20-350.6-10.9-1.3
Mon Nov 29 - 2 AM0-20Clear0 / 0-3N/15-250.7-1.10.9-1.3
2 PM0-20Clear0 / 01N/20-30NaN1.5-2.5
Tue Nov 30 - 2 AM20-406-750 / 10-4.5NNW/15-251-1.44-6
2 PM60-804-770 / 300ENE/10-20NaN4-8
Wed Dec 01 - 2 AM80-1004-790 / 50-3NE/10-201.3-1.74-8
2 PM80-1004-790 / 502NE/5-15NaN4-6
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
Sat Nov 27 - Sun Nov 28 17:51 18:59 5:21 6:29 0:52 N/A 40 11 24.3 9 24
Sun Nov 28 - Mon Nov 29 17:51 18:59 5:22 6:30 1:47 N/A 30 12 12.8 3 39
Mon Nov 29 - Tue Nov 30 17:51 18:59 5:22 6:30 2:45 N/A 20 13 02.2 -2 26
Tue Nov 30 - Wed Dec 01 17:51 18:59 5:23 6:31 3:44 N/A 12 13 53.6 -8 35
Wed Dec 01 - Thu Dec 02 17:51 18:59 5:23 6:32 4:48 N/A 5 14 48.1 -14 27
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 29 November 2021.
Additional Information
For public road conditions and snow report message please call (808) 935-6268.
This message is also available at the MKWC road conditions page.
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