Current Conditions
Temp2.2 C
RH22 %
WindENE 0 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Monday 26 January (0300 UTC Tuesday 27 January) 2015
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 1.5 C this evening and 1 C tomorrow morning. Winds will be light and from the north, while seeing will start out near 0.7 arcseconds, but will improve toward 0.5 arcseconds through the night. Precipitable water is expected to be in the 1.5-2 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 7 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 clear through the next 5 nights.

Precipitable water will linger primarily near 1.5-1.75 mm for the next 2 nights, increase toward 2 mm for Wednesday and Thursday night and perhaps 3 mm for Friday night.

While lingering mid-level turbulence will likely contribute to poor seeing for this evening, this turbulence is slated to subside, allowing seeing to improve as the night progresses. Better than average seeing is expected as minimal turbulence prevails at and above the summit for Tuesday and Wednesday night. However, increasing summit-level winds may stir up boundary layer turbulence and contribute to poor seeing for Thursday and Friday night.

No change since the morning forecast...The mid/low-level ridge will continue to sit over/near the Islands and promote steady/strong large-scale subsidence in the area through the week. This will help maintain a well-defined tradewind inversion at or below 7 thousand feet and ensure the summit remains dry and stable throughout the forecast period. Skies will also remain predominately clear as a zonal westerly jet well to the north of the state keeps high clouds at bay. Lingering mid-level turbulence associated with a decayed front may contribute to poor seeing for this evening, but that turbulence is expected to taper allowing seeing to improve as the night progresses and especially the following 2 nights. There is a possibility that the westerly jet will drift closer to the state, which could strengthen summit-level winds and bring minor mid-level moisture to the area later in the week. The former will likely increase boundary layer turbulence and degrade seeing, while the latter could push PW toward 3 mm for Thursday and/or 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 Jan 26 - 8 PM0-5Clear0 / 01.5NE/0-100.5-0.81.5-2
Tue Jan 27 - 2 AM0-5Clear0 / 01NNE/0-100.45-0.651.5-2
2 PM0-20Clear0 / 06.5WNW/5-15NaN1.5-2
8 PM0-5Clear0 / 02WNW/5-150.45-0.551.25-1.75
Wed Jan 28 - 2 AM0-5Clear0 / 01.5WNW/5-150.4-0.51.25-1.75
2 PM0-20Clear0 / 07.5W/5-15NaN1.25-1.75
8 PM0-5Clear0 / 02SW/10-200.4-0.51.5-2
Thu Jan 29 - 2 AM0-5Clear0 / 02SW/10-200.4-0.51.5-2
2 PM0-20Clear0 / 06SW/15-30NaN1.5-2.5
Fri Jan 30 - 2 AM0-5Clear0 / 01SW/15-300.5-0.91.5-2.5
2 PM0-20Clear0 / 05.5WSW/15-30NaN2-4
Sat Jan 31 - 2 AM0-5Clear0 / 00WSW/15-300.5-0.92-3
2 PM0-20Clear0 / 05WSW/15-30NaN2-4
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 Jan 26 - Tue Jan 27 18:20 19:27 5:42 6:49 N/A 0:58 52 2 29.0 12 15
Tue Jan 27 - Wed Jan 28 18:20 19:27 5:42 6:49 N/A 1:55 62 3 22.9 15 07
Wed Jan 28 - Thu Jan 29 18:21 19:28 5:42 6:49 N/A 2:49 72 4 16.9 17 08
Thu Jan 29 - Fri Jan 30 18:22 19:28 5:42 6:48 N/A 3:42 81 5 10.8 18 14
Fri Jan 30 - Sat Jan 31 18:22 19:29 5:42 6:48 N/A 4:33 88 6 04.2 18 23
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 27 January 2015.
Additional Information
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This message is also available at the MKWC road conditions page.
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