Current Conditions
Temp5.8 C
RH6 %
WindSE 3 mph
RoadOpen (4x4 only)
Mauna Kea Observatories Forecast
5 PM HST Monday 30 November (0300 UTC Tuesday 1 December) 2015
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 4 C, with light and variable winds throughout the night. Seeing will be near 0.45-0.5 arcseconds, while precipitable water is expected to be in the 1-1.2 mm range for the night.
A well-defined tradewind inversion will continue to cap low-level moisture near 7 thousand feet and ensure a dry and stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Skies overhead will remain predominately clear through at least Wednesday night. Banding thin high clouds may start to build in from the south on Thursday and may scrape the southern half of the Big Island for that night and Friday night.

Precipitable water is expected to linger near 1.1-1.3 mm for the next 2 nights, then slip toward 0.8-0.9 mm for the following 3 nights (there is a slight chance it will dip toward 0.7 mm for Friday night).

Lighter summit-level winds combined with predominately weak turbulence in the free atmosphere, should allow for better than average seeing throughout most of the forecast period. There is a slight chance that a patch of upper-level turbulence will briefly pass through the area, which may degrade seeing toward more average-like values for Thursday night.

No change since the morning forecast...The mid/low-level ridge will continue to sit over or just north of the state and promote steady/strong large-scale subsidence in the area through the week. This subsidence will easily maintain a well-defined tradewind inversion near 7 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. It should also help PW to linger near 1 mm (or less) during this time. Flow aloft will also maintain a fairly zonal orientation, which should keep turbulence in the atmosphere to a minimum throughout most of the forecast period. The only exception could be as the northern fringe of the sub-tropical jet builds in from the south for Thursday night. While the STJ is slated to broaden a bit, reducing the turbulence in the area for the following night, there is a chance that the jet will bring high clouds along the southern skies for both Thursday and Friday night.
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)
Mon Nov 30 - 8 PM0-5Clear0 / 04SE/0-100.4-0.51-1.2
Tue Dec 01 - 2 AM0-5Clear0 / 04NW/0-100.4-0.51-1.2
2 PM0-20Clear0 / 09WNW/0-10NaN1-1.5
8 PM0-5Clear0 / 04.5NW/5-150.4-0.51-1.2
Wed Dec 02 - 2 AM0-5Clear0 / 04.5NNW/5-150.4-0.61-1.2
2 PM0-20Clear0 / 010NNE/5-15NaN0.8-1.2
8 PM0-5Clear0 / 05NE/5-150.4-0.60.8-1
Thu Dec 03 - 2 AM0-5Clear0 / 04ENE/5-150.45-0.550.8-1
2 PM0-209.5-100 / 09SE/0-10NaN0.8-1.2
Fri Dec 04 - 2 AM10-309.5-100 / 04ESE/0-100.45-0.650.8-1
2 PM20-409-100 / 08.5ENE/0-10NaN0.8-1.2
Sat Dec 05 - 2 AM10-309.5-100 / 04NE/5-150.4-0.60.7-1
2 PM0-20Clear0 / 010ENE/10-20NaN0.8-1.2
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
Mon Nov 30 - Tue Dec 01 17:51 18:59 5:22 6:31 22:28 N/A 67 9 19.6 12 09
Tue Dec 01 - Wed Dec 02 17:51 18:59 5:23 6:31 23:19 N/A 58 10 08.1 8 57
Wed Dec 02 - Thu Dec 03 17:51 19:00 5:24 6:32 0:09 N/A 48 10 54.7 5 27
Thu Dec 03 - Fri Dec 04 17:51 19:00 5:24 6:32 0:57 N/A 39 11 40.0 1 48
Fri Dec 04 - Sat Dec 05 17:52 19:00 5:25 6:33 1:45 N/A 30 12 24.7 -1 54
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 1 December 2015.
Additional Information
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This message is also available at the MKWC road conditions page.
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