Current Conditions
Temp8.2 C
RH28 %
WindSE 13 mph
Mauna Kea Observatories Forecast
5 PM HST Wednesday 26 November (0300 UTC Thursday 27 November) 2014
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 3 C this evening and 2.5 C tomorrow morning. Winds will be from the west at 5-15 mph, with seeing around 0.4-0.5 arcseconds. Precipitable water is expected to be in the 1.75-2.25 mm range for the night.
The tradewind 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 will remain predominately clear through midnight tomorrow, but there is a possibility that a small patch of mid/upper-level clouds will pass over and especially along the northern skies on Friday. Skies will open up again for the weekend.

Precipitable water is expected to linger near 2 mm for tonight, increase toward 2.5-3 mm for the following 3 nights, then slip back to 1 mm on Sunday night.

Relatively calm/uniform flow at and above the summit will keep turbulence in the atmosphere to a minimum and should allow for better than average seeing through tomorrow night. An increase in upper-level turbulence is expected to degrade seeing through Friday, and probably contribute to poorer than average seeing over the weekend.

No change 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 into next week. This will easily maintain a well-defined tradewind inversion near 7-8 thousand feet and ensure the summit steers free of moisture through the next 5 nights. Relatively zonal flow will prevail aloft, which will keep upper-level instability to a minimum and the bulk of the high clouds to the north or south of the summit area during most of that time (the only exception when a patch briefly passes closer to the north on Friday). It will also allow for little turbulence in the atmosphere and likely better than average seeing during the next 2 nights. However, the sub-tropical jet is expected to build in overhead on Friday, which could increase upper-level turbulence and contribute to slightly poorer than average seeing over the weekend.

Please Note: There will be no forecasts tomorrow, Thursday Nov. 26, in observance of Thanksgiving. The normal forecast will resume on Friday.
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 Nov 26 - 8 PM0-5Clear0 / 03W/5-150.4-0.51.75-2.25
Thu Nov 27 - 2 AM0-5Clear0 / 02.5W/5-150.4-0.51.75-2.25
2 PM0-20Clear0 / 07.5WNW/0-10NaN2-3
8 PM0-10Clear0 / 02W/0-100.4-0.52.5-3.5
Fri Nov 28 - 2 AM0-208-90 / 01.5SW/0-100.45-0.552.5-3.5
2 PM10-307-90 / 06W/5-15NaN2-3
8 PM0-208-90 / 01WNW/5-150.45-0.652-3
Sat Nov 29 - 2 AM0-10Clear0 / 00.5WNW/5-150.5-0.72-3
2 PM0-20Clear0 / 05WNW/5-15NaN2-3
Sun Nov 30 - 2 AM0-5Clear0 / 00NNW/0-100.5-0.81.5-2.5
2 PM0-20Clear0 / 05NNE/0-10NaN1-2
Mon Dec 01 - 2 AM0-5Clear0 / 00.5E/0-100.4-0.80.8-1.2
2 PM0-20Clear0 / 05.5S/0-10NaN0.8-1.2
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
Wed Nov 26 - Thu Nov 27 17:51 18:59 5:20 6:28 N/A 22:21 27 20 35.7 -13 41
Thu Nov 27 - Fri Nov 28 17:51 18:59 5:21 6:29 N/A 23:21 38 21 31.6 -10 12
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
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 28 November 2014.
Additional Information
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