Current Conditions
Temp6.4 C
RH6 %
WindS 9 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Friday 12 February (0300 UTC Saturday 13 February) 2016
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 4.5 C, with winds from the ENE at 10-20 mph and seeing around 0.4-0.45 arcseconds. Precipitable water is expected to be in the 0.55-0.7 mm range for the night.
Discussion
The tradewind inversion will continue to cap the limited supply of low-level moisture near 6-7 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 predominately clear through at least Monday night. There is a possibility that a band of high clouds will fill in out of the southwest and briefly pass over the summit area through Tuesday night.

Precipitable water is expected to linger near 0.6-0.65 mm for the next 3 nights, then drift toward 1 mm for Monday night and perhaps toward 3-4 mm for Tuesday night.

Calm skies and deep subsidence in the free atmosphere should allow seeing to settle in near 0.4-0.5 arcseconds through the next 3 nights. There is a chance that building upper-level turbulence will degrade seeing toward poorer than average values for Monday night; some minor improvement is possible for Tuesday night.

No change since the morning forecast...A deep ridge will continue to sit over the state, before the upper-half weakens in response to a trough filling in from the NW for the early part of next week. Nonetheless, the trough is not expected to affect the stability of the atmosphere, allowing strong/steady large-scale subsidence to prevail in the area throughout the forecast period. This subsidence will easily maintain a well-defined inversion near 6-7 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. In addition, the extra subsidence provided by the upper-portion of the ridge will keep high clouds at bay and allow PW and seeing to settle in near toward 0.6-0.65 mm and 0.4-0.5 arcseconds, respectively, over the next 3 nights. There is a possibility that the eastern portion of the building trough will briefly redevelop the sub-tropical jet over the Big Island for the early part of next week. The could bring upper-level turbulence (mainly for Monday night) and mid-level moisture to the area, driving both seeing and PW upwards during that time. There is also a good chance that the trough will help fire off convection far to the southwest of the state, which the jet may briefly transport its cirrus exhaust over the southern half of the state between late Tuesday evening and midnight Wednesday. All in all, expect excellent observing conditions/skies for the next 3 nights, with more mediocre skies prevailing for Monday and Tuesday night.

Please Note: There will be no forecasts on Monday, February 15, in observance of Presidents' Day. The normal forecast schedule will resume on Tuesday, February 16.
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 Feb 12 - 8 PM0-5Clear0 / 04.5ENE/10-200.4-0.50.55-0.7
Sat Feb 13 - 2 AM0-5Clear0 / 04.5ENE/10-200.35-0.450.55-0.7
2 PM0-20Clear0 / 09ENE/5-15NaN0.6-1
8 PM0-5Clear0 / 04.5E/10-200.35-0.450.55-0.7
Sun Feb 14 - 2 AM0-5Clear0 / 04E/10-200.4-0.50.55-0.7
2 PM0-20Clear0 / 09ESE/10-20NaN0.6-1
8 PM0-5Clear0 / 03.5ESE/5-150.4-0.50.55-0.7
Mon Feb 15 - 2 AM0-5Clear0 / 03E/5-150.4-0.50.55-0.7
2 PM0-20Clear0 / 08NW/5-15NaN0.6-1
Tue Feb 16 - 2 AM0-5Clear0 / 02.5WNW/5-150.5-0.80.8-1.2
2 PM0-20Clear0 / 07NW/5-15NaN1-2
Wed Feb 17 - 2 AM40-60Clear0 / 02WNW/5-150.4-0.82-4
2 PM0-20Clear0 / 07NW/10-20NaN2-4
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
Sat Feb 13 - Sun Feb 14 18:29 19:35 5:37 6:42 N/A 0:01 39 2 44.7 11 35
Sun Feb 14 - Mon Feb 15 18:30 19:35 5:37 6:42 N/A 1:00 50 3 41.0 14 38
Mon Feb 15 - Tue Feb 16 18:30 19:35 5:36 6:41 N/A 1:59 61 4 37.8 16 47
Tue Feb 16 - Wed Feb 17 18:31 19:36 5:36 6:41 N/A 2:55 72 5 34.8 17 56
Wed Feb 17 - Thu Feb 18 18:31 19:36 5:35 6:40 N/A 3:49 81 6 31.3 18 03
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 15 February 2016.
Additional Information
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This message is also available at the MKWC road conditions page.
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