Current Conditions
Temp2.4 C
RH28 %
WindSE 17 mph
RoadOpen (4x4 only)
Mauna Kea Observatories Forecast
5 PM HST Friday 27 November (0300 UTC Saturday 28 November) 2015
Small/Moderate chances for short episodes of high RH
Cloud Cover and Fog/Precipitation Forecast
Moisture at the summit will slowly increase through this evening and tonight and so will cloud cover. Summit skies will be mostly cloudy by the second half of the night and episodes of high relative humidity are likely then.
Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C this evening and 2.5 C tomorrow morning. Winds will be from the NW at 15-25 mph (increasing through the night), with seeing near 0.6-0.7 arcseconds. Precipitable water is expected to linger close or exceed 4 mm through the night.
In spite of a strenghtening tradewind inversion and a stabilizing atmosphere, the joint effect of remnant of a front at the surface and a minor upper level disturbance, will cause moisture to move back toward the Big Island, starting late today. Therefore moisture will increase at the summit level through this evening/tonight. The atmosphere will quickly stabilize tomorrow and drier air masses will characterize the rest of this forecasting period.

High broken clouds will dissipate in time through today. Nevertheless more mid/high clouds will approach the summit skies late this evening from the NW and are likely to block at least 50% of the summit skies, particularly during the second half of the night. A clearing trend will follow and mostly clear skies are expected for the remaining four nights.

Precipitable water will linger close or exceed 4 mm tonight. It will decrease afterward and range between 1.5 and 2 mm on Saturday night. It will range between 2.5 and 3 mm on Sunday night and drop back to 1.5 mm on the remaining two nights.

Observing conditions will be average to less than average for at least one more night, as turbulence associated with a minor upper level disturbance will cross the area tonight. Increase in the boundary layer turbulence is also possible tonight and possible for part of tomorrow as winds at the summit will pick up some. Conditions will improve through the weekend and the rest of this forecast period.

Not much is changed since the morning forecast... The current weather scenario is dominated by a strenghtening ridge to the North of the State and the remnant of a front over the Northern islands. A short wave trough embedded in the Sub Tropical Jet (STJ) will push the front back Southeastward and across the State through tonight. The tradewind inversion will strenghten afterward and a more typical weather pattern will establish then. The passage of this minor upper level disturbance will cause turbulence to increase in the free atmosphere. Meanwhile, winds will increase at the surface as well, therefore inflating ground turbulence for tonight. Cloud and moisture will also be advected over, increasing the chances for short episodes of high relative humidity, particularly for late tonight early tomorrow morning. Overall observing and weather conditions will improve tomorrow and through the weekend and will remain in the fair/average range throughout this forecast period.
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 27 - 8 PM10-308-930 / 03.5WNW/15-250.35-0.754-6
Sat Nov 28 - 2 AM30-507-860 / 52.5NW/15-250.45-0.854-8
2 PM50-706-820 / 09.5NE/15-25NaN2-3
8 PM10-308-90 / 04NE/20-300.5-0.91-2
Sun Nov 29 - 2 AM0-20Clear0 / 02NE/20-300.45-0.851.5-2
2 PM0-20Clear0 / 09NE/15-25NaN2-3
8 PM0-20Clear0 / 03.5NE/10-200.4-0.82.25-2.75
Mon Nov 30 - 2 AM0-20Clear0 / 03ENE/10-200.35-0.752.5-3
2 PM0-20Clear0 / 09.5ESE/5-15NaN1.5-2.5
Tue Dec 01 - 2 AM0-20Clear0 / 04SSE/5-150.35-0.751.25-1.75
2 PM0-20Clear0 / 010S/5-15NaN1.5-2.5
Wed Dec 02 - 2 AM0-20Clear0 / 04NNW/5-150.35-0.751-1.5
2 PM0-20Clear0 / 09E/10-20NaN1-2
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
Sun Nov 29 - Mon Nov 30 17:51 18:59 5:22 6:30 21:35 N/A 76 8 28.5 14 53
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
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 30 November 2015.
Additional Information
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