Current Conditions
Temp0.9 C
RH7 %
WindSSE 28 mph
Mauna Kea Observatories Forecast
5 PM HST Thursday 18 December (0300 UTC Friday 19 December) 2014
Moderate/strong winds
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, but there is a possibility for patches of high clouds in the area, mainly for this evening.
Summary of Key Meteorological Variables
Summit temperatures will be near 0 C, with winds from the east at 20-35 mph and seeing around 0.9-1 arcseconds. Precipitable water is expected to be in the 1-1.2 mm range for the night.
The tradewind inversion will continue to cap low-level moisture at or below 8 thousand feet and ensure a dry and stable mid/summit-level air mass through at least midnight Sunday. There is a possibility that the inversion will weaken/lift toward 12-13 thousand feet, which will raise the stakes on fog, ice and high humidity for much of Monday and into Tuesday. Daytime clouds will be minimal and short-lived through Sunday, but could pick up for the early part of next week.

There is a possibility for patches of high clouds in the area through this evening. Any clouds will shift off toward the southeast by midnight, leaving predominately clear skies through Sunday night. There is a chance banding high clouds will set up just southeast of the Big Island as well as summit-level clouds for Monday night.

Precipitable water is expected to increase toward 1-1.2 mm for tonight, then slip back to 0.8-0.9 mm for the following 2 nights. There is a chance that it will increase to 1-2 mm again for Sunday night and 2-4 mm for Monday night.

Increasing boundary layer turbulence will contribute to poor/bad seeing over the next 3 nights. Although the boundary turbulence is slated to subside on Sunday, strengthening turbulence in the free atmosphere probably limit much improvement in seeing for Sunday and Monday night.

No change since the morning forecast...A new ridge filling in from the west will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area through the weekend. While this ridge will help maintain the inversion near 7-8 thousand feet and ensure a dry/stable summit-level air mass through the next 4 nights, associated moderate/strong easterly winds is expected to stir up boundary layer turbulence and contribute to poor/bad seeing through Saturday night. On other hand, mostly clear/dry air will prevail at and/above the summit, which should allow for clear skies and low PW, particularly for Friday, Saturday and possibilty Sunday night. A sharp trough is expected to develop to the northwest and dig toward the state shoving the ridge off toward the east late Sunday night. There is a chance that this trough will destabilize the atmosphere, increasing the risk for fog, ice and perhaps light flurries at the summit for the early part of next week. In addition, global models are projecting another trough to develop over/near the Islands around Christmas. As a result, there is a chance poor/wet maybe evening snowy (white) conditions will plague the summit for good part of next week.
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)
Thu Dec 18 - 8 PM0-208.5-90 / 00E/20-350.7-1.11-1.2
Fri Dec 19 - 2 AM0-10Clear0 / 00E/20-350.7-1.31-1.2
2 PM0-20Clear0 / 04E/20-35NaN0.8-1.2
8 PM0-5Clear0 / 0-1E/20-350.8-1.40.7-0.9
Sat Dec 20 - 2 AM0-5Clear0 / 0-1E/25-400.8-1.60.7-0.9
2 PM0-20Clear0 / 04.5ESE/25-40NaN0.8-1.2
8 PM0-5Clear0 / 0-1ESE/25-400.7-1.30.8-1
Sun Dec 21 - 2 AM0-5Clear0 / 0-1.5ESE/20-350.6-1.20.8-1
2 PM0-20Clear0 / 04.5SE/15-30NaN1-2
Mon Dec 22 - 2 AM0-20Clear10 / 5-1WSW/5-150.5-0.90.8-1.2
2 PM60-804-660 / 203SW/10-20NaN3-6
Tue Dec 23 - 2 AM20-409-1040 / 10-3SW/15-300.6-1.22-4
2 PM60-804-550 / 154N/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
Thu Dec 18 - Fri Dec 19 17:56 19:05 5:32 6:41 4:21 N/A 8 15 28.7 -15 47
Fri Dec 19 - Sat Dec 20 17:57 19:06 5:33 6:42 5:19 16:15 4 16 24.1 -17 41
Sat Dec 20 - Sun Dec 21 17:57 19:06 5:33 6:42 6:18 17:09 1 17 21.7 -18 37
Sun Dec 21 - Mon Dec 22 17:58 19:07 5:34 6:43 7:16 18:07 0 18 21.0 -18 26
Mon Dec 22 - Tue Dec 23 17:58 19:07 5:34 6:43 N/A 19:08 3 19 20.7 -17 06
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 19 December 2014.
Additional Information
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This message is also available at the MKWC road conditions page.
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