Current Conditions
Temp3.9 C
RH10 %
WindNW 4 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Tuesday 25 November (0300 UTC Wednesday 26 November) 2014
Warning(s)
None
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 3.5 C this evening and 3 C tomorrow morning. Winds will be from the WSW at 5-15 mph, while seeing will likely start out near 0.6 arcseconds, but improve toward 0.45 arcseconds for the morning hours. Precipitable water is expected to be in the 1.25-1.75 mm range for the night.
Discussion
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 Thursday, 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 Saturday.

Precipitable water will linger near 1.5 mm through tomorrow evening, then increase toward 2 early Thursday morning and probably 3 mm for later that night and perhaps most of Friday night. It should settle back in near 1 mm again for Saturday night.

While lingering mid-level turbulence may contribute to slightly poorer than average seeing for this evening, this turbulence is slated as the night progresses, allowing seeing to settle in near 0.4-0.5 arcseconds probably for the remainder of the forecast period.

No change since the morning forecast...A relatively deep ridge will continue to sit over or just north of the Big Island and promote steady/strong large-scale subsidence in the area probably through the week. This will help maintain a well-defined tradewind inversion primarily near 8 thousand feet and ensure the summit remains dry and stable through the next 5 nights. Predominately westerly flow will prevail aloft, which should keep turbulence in a free atmosphere to a minimum and likely allow for better than average seeing throughout most of the forecast period. The only exception could be a result of lingering mid/low-level turbulence, which may contribute to slightly poorer than average seeing for this evening. Skies will also remain primarily clear, with the bulk of the clouds passing quickly to the north of the state through the week. There is a slight possibility that a small patch of mid/upper-level clouds will scrape the northern tip of the Big Island mainly 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)
Tue Nov 25 - 8 PM0-5Clear0 / 03.5WSW/5-150.5-0.71.25-1.75
Wed Nov 26 - 2 AM0-5Clear0 / 03WSW/5-150.4-0.51.25-1.75
2 PM0-20Clear0 / 08WSW/5-15NaN1.25-1.75
8 PM0-5Clear0 / 03WSW/5-150.39-0.491.25-1.75
Thu Nov 27 - 2 AM0-5Clear0 / 02.5W/0-100.35-0.451.5-2
2 PM0-20Clear0 / 07.5WNW/0-10NaN2-3
8 PM0-1Clear0 / 02NNW/0-100.35-0.452-3
Fri Nov 28 - 2 AM0-207-80 / 01.5WSW/0-100.4-0.52.5-3.5
2 PM10-307-90 / 06NW/0-10NaN2.5-3.5
Sat Nov 29 - 2 AM0-208-90 / 00.5NW/0-100.35-0.552-3
2 PM0-20Clear0 / 06W/0-10NaN1-2
Sun Nov 30 - 2 AM0-5Clear0 / 01NNE/0-100.4-0.60.8-1.2
2 PM0-20Clear0 / 06ENE/0-10NaN1-2
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
Tue Nov 25 - Wed Nov 26 17:51 18:58 5:20 6:28 N/A 21:21 18 19 38.5 -16 22
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
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Wednesday 26 November 2014.
Additional Information
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