Current Conditions
Temp3.1 C
RH17 %
WindS 7 mph
Mauna Kea Observatories Forecast
5 PM HST Friday 17 October (0300 UTC Saturday 18 October) 2014
Fog/high humidity
Moderate/strong winds
Chance for convection and rain
Cloud Cover and Fog/Precipitation Forecast
Fog, high humidity, clouds, rain and perhaps convection will plague the summit through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 2 C this evening and 1 C for tomorrow morning. Winds will be from the SE at 40-60 mph, while precipitable water and seeing are expected to exceed 4 mm and 1 arcsecond, respectively, through the night.
The atmosphere near the Big Island will remain saturated and unstable, which will allow for extensive fog, humidity near 100% and/or rain at the summit probably through at least Sunday evening. There is also a possibility for deep convection in the area and periods of heavy rain mainly between this evening and tomorrow evening. The odds on fog, high humidity and especially convection and rain will subside as the inversion rebuilds near 6-7 thousand feet and the air mass below 16 thousand feet dries out through Sunday night and particularly for the early part of next week. Extensive daytime clouds are expected through Sunday, but should taper a bit for Monday and Tuesday, then pick up again on Wednesday.

Broken to overcast thick clouds will continue to blanket summit skies for at least the next 2 nights. There is a possibility that these clouds will begin to gradually breakdown and/or shift off toward the northwest around Sunday evening. Still, there is a possibility for lingering mid-level clouds probably through Tuesday night.

Precipitable water will continue to exceed 4 mm through the next 5 nights.

Strong turbulence throughout the atmosphere combined with wet/unstable conditions and cloudy skies will contribute to bad seeing for the next 2 nights. There is a possibility that skies and conditions will improve through Sunday night, but poor seeing will likely prevail due to lingering mid-level turbulence probably Monday evening. There is a chance that seeing will start to dip back toward average-like values for Tuesday night.

No change since the morning forecast...There is very good consensus that the center of Hurricane/Tropical Storm Ana will pass roughly 200 km to the south and parallel to the state over the next several days. Unfortunately, deep moisture and widespread instability along the storm's right flank will saturate the atmosphere near the Big Island over the next 48-60 hours. This will result in extensive fog, humidity near 100%, overcast skies and probably periods of rain at the summit through Sunday evening. There is also a possibility deep convection in the area as well as heavy rain and strong winds at the summit mainly as Ana passes to the southwest of the Big Island over the next 36 hours. Winds are slated to rapidly subside through Sunday and there is very good chance that the inversion will begin to rebuild as Ana shifts further off toward the west through that night. Although this should help to diminish the risk for moisture at the summit for the early part of next week, linger mid/upper-level moisture/clouds could still result in periods of extensive cloud cover, high humidity and likely PW > 4 mm during that time. All in all expect inoperable conditions/skies for the next 2 nights, and improving but still less than mediocre conditions/skies for the following 3 nights. Finally, it should be noted that there is a possibility that residual moisture for Ana and/or a passing/decayed cold front may make a return to the area and perhaps saturate the air mass again around the middle part of next week. This should be short-lived (if it happens at all), but there is a good chance that the summit may not see normal conditions/skies for another 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)
Fri Oct 17 - 8 PM80-1004-10100 / 952SE/40-601-315-20
Sat Oct 18 - 2 AM80-1004-10100 / 951SE/40-601-315-20
2 PM80-1004-10100 / 954SSE/30-45NaN15-20
8 PM80-1004-1095 / 801SSE/20-351-210-15
Sun Oct 19 - 2 AM80-1004-1095 / 751SSE/15-301-210-15
2 PM80-1004-1090 / 754SSE/10-20NaN10-15
8 PM70-904.5-1075 / 502SE/10-200.7-1.38-12
Mon Oct 20 - 2 AM60-805-960 / 302SE/5-150.5-1.18-12
2 PM40-604-850 / 106SE/5-15NaN6-10
Tue Oct 21 - 2 AM40-605-825 / 52SE/0-100.5-14-8
2 PM30-504-830 / 57N/0-10NaN4-8
Wed Oct 22 - 2 AM20-406-820 / 51.5N/0-100.4-0.84-8
2 PM60-804-860 / 205ENE/0-10NaN6-10
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 Oct 19 - Mon Oct 20 18:04 19:09 5:05 6:09 3:31 N/A 11 11 11.0 2 06
Mon Oct 20 - Tue Oct 21 18:04 19:08 5:05 6:10 4:20 N/A 6 11 56.4 -1 42
Tue Oct 21 - Wed Oct 22 18:03 19:08 5:05 6:10 5:10 16:50 2 12 42.6 -5 29
Wed Oct 22 - Thu Oct 23 18:02 19:07 5:06 6:10 6:02 17:30 0 13 30.2 -9 07
Thu Oct 23 - Fri Oct 24 18:02 19:07 5:06 6:11 6:55 18:11 0 14 19.6 -12 24
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 20 October 2014.
Additional Information
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