Current Conditions
Temp0.3 C
RH9 %
WindNE 40 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Tuesday 11 December 2018
Warning(s)
Moderate/strong winds
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 5.5 C this afternoon and 0 C for the night. Winds will be from the east at 25-40 mph for today, switching to a more NE direction through the night. Seeing will exceed 1 arcsecond, while precipitable water is expected to be in the 0.6-0.8 mm range for the night.
Discussion
A strong well-defined inversion will continue to cap low-level moisture at or below 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.

Skies overhead will remain predominately clear throughout most of the forecast period. There is a chance that a band of high clouds will approach from the south and briefly scrape the Big Island near sunrise on Friday.

Precipitable water is expected to linger near 0.7-0.8 mm through the next 4 nights, then increase toward 1-1.5 mm for Saturday night.

A mixture of boundary layer and low-level turbulence will contribute to poor/bad seeing over the next 5 nights.

A well-defined relatively deep mid/low-level ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area probably well into next week. This subsidence will easily maintain a well-defined inversion near 7-8 thousand feet and ensure a dry and stable summit-level air mass throughout the forecast period. In addiiton, this subsidence, combined with very dry air flowing along the western fringe of a mid/upper-level low to the east will also allow PW to settle in near 0.7-0.8 mm for at least the next 4 nights. There is a chance that PW will increase as minor mid/upper-level moisture flows out of the westerly jet to the north and over the summit area during the weekend. Unfortunately, winds at the summit will remain quite strong as the aforementioned trough tightens the wind gradient along the SE of the ridge over the next 2 nights. While there is a chance that winds will taper a bit as the trough begins to lift eastward around Thursday, a new ridge reinforcing the current ridge will help restrengthen winds on Friday and over the weekend. Consequently, there is a good chance that boundary layer and/or low-level turbulence will contribute to poor/bad seeing over the next 5 nights.
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)
Tue Dec 11 - 2 PM0-20Clear0 / 05.5E/25-40NaN0.6-1
8 PM0-5Clear0 / 00ENE/25-400.9-1.50.6-0.8
Wed Dec 12 - 2 AM0-5Clear0 / 00NE/25-400.9-1.50.6-0.8
2 PM0-20Clear0 / 04NE/20-35NaN0.8-1.2
8 PM0-5Clear0 / 0-1NE/15-300.8-1.20.7-0.9
Thu Dec 13 - 2 AM0-5Clear0 / 0-1NNE/15-300.7-1.10.7-0.9
2 PM0-20Clear0 / 04NE/10-20NaN0.8-1.2
8 PM0-5Clear0 / 0-1ENE/15-300.6-10.7-0.9
Fri Dec 14 - 2 AM0-5Clear0 / 0-0.5ENE/15-300.7-1.10.7-0.9
2 PM0-20Clear0 / 04ENE/20-35NaN0.8-1.2
Sat Dec 15 - 2 AM0-209-100 / 0-0.5ENE/20-350.7-1.30.65-0.9
2 PM0-209-100 / 06.5NE/20-35NaN0.8-1.2
Sun Dec 16 - 2 AM0-5Clear0 / 01.5NE/20-350.7-1.31-1.5
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
Tue Dec 11 - Wed Dec 12 17:54 19:02 5:29 6:37 N/A 21:56 22 21 16.5 -17 37
Wed Dec 12 - Thu Dec 13 17:54 19:03 5:29 6:38 N/A 22:46 30 22 03.9 -14 43
Thu Dec 13 - Fri Dec 14 17:54 19:03 5:30 6:39 N/A 23:35 39 22 50.2 -11 13
Fri Dec 14 - Sat Dec 15 17:55 19:04 5:30 6:39 N/A 0:25 48 23 36.0 -7 13
Sat Dec 15 - Sun Dec 16 17:55 19:04 5:31 6:40 N/A 1:14 58 0 21.8 -2 52
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Tuesday 11 December (0300 UTC Wednesday 12 December) 2018.
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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