Current Conditions
Temp3.0 C
RH30 %
WindSE 0 mph
Mauna Kea Observatories Forecast
5 PM HST Monday 29 September (0300 UTC Tuesday 30 September) 2014
High humidity
Chance for fog/rain and convection
Cloud Cover and Fog/Precipitation Forecast
Humidity will continue to linger near or exceed 80% and there is a high risk for fog/rain at the summit as well as clouds and convection in the area through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1 C this evening and 0.5 C tomorrow morning. Winds will be from the ESE at 5-15 mph, while seeing and precipitable water is expected to 1 arcsecond and 4 mm, respectively through the night.
After briefly strengthening last night, the inversion is slated to fall apart over the next 6-12 hours, perhaps leading to a fairly saturated atmosphere between late this evening and early tomorrow afternoon. The inversion is slated to recover again near 8 thousand feet through tomorrow night, but there is a chance that humidity will continue to linger near 60-80% for that night, and there is also a possibility that the inversion will periodically lift back toward 12 thousand feet for the remainder of the week. Consequently, there is risk for fog, rain and/or high humidty at the summit throughout the forecast period, particularly tonight. There is also a chance for convection in the area over the next 24 hours. Extensive afternoon clouds are possible throughout the forecast period.

Broken thick mid/upper-level clouds are slated to fill in and/or develop over the summit area, contributing to extensive cloud cover for tonight and probably a good portion of tomorrow night. In addition, band of high clouds is also expected to set up along the southeastern skies late tomorrow afternoon and persist probably through Thursday night. This band is slated to shift off toward the east early Friday morning, leaving mostly clear skies for that night.

Precipitable water is expected to linger near or exceed 4 mm throughout the forecast period.

Upper-level turbulence/instability and wet summit-level conditions will contribute to poor/bad seeing for tonight and probably most of tomorrow night. Summit-level conditions area expected to improve a bit for the remainder of the week, but there is a possibility for lingering free-atmospheric turbulence and instability. Regardless, seeing should settle back in near average/poor values during that time.

Not much change since the morning forecast, though latest model run expects the trough to depart eastward at a slower pace later in the week....The upper-level low to the southwest of the state is slated to fall apart over the next 24 hours and open up to quasi-stationary trough that will persist in the area before shifting east of the Big Island around Friday/Saturday. Unfortunately, another batch of instability and moisture is expected to drift over the Big Island before the low dissipates, which could lead to fairly saturated environment between late this evening and early tomorrow afternoon. Thus, there is a high risk for fog, high humidity and rain at the summit as well as another round of convection and deep/thick clouds in the area for tonight. The atmosphere will try to restabilize as a weak mid/low-level ridge to the north of state tries to re-establish its influence late tomorrow night and for remainder of the forecast period. However, the persistent trough may periodically deepen the low-level cloud field and perhaps allow for more short-lived fog or spike humidity at the summit during that time (particularly as the trough axis drifts over the Big Island between early Thursday evening and late Friday night). The southeastern half of the trough will also stream high clouds along the southern skies especially for Tuesday, Wednesday and part of Thursday night. Conditions and especially skies should improve as the trough axis shifts over the weekend.
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 Sep 29 - 8 PM70-904-875 / 501E/0-100.8-1.66-10
Tue Sep 30 - 2 AM70-904-890 / 600.5E/0-101-26-10
2 PM80-1004-1075 / 255NNW/0-10NaN6-10
8 PM60-806-1060 / 151.5N/5-150.7-1.34-8
Wed Oct 01 - 2 AM40-607-1050 / 101.5WNW/0-100.6-14-8
2 PM60-804-1060 / 156NW/0-10NaN4-8
8 PM20-408-1025 / 52WSW/0-100.5-0.94-6
Thu Oct 02 - 2 AM10-308.5-1020 / 51.5WSW/5-150.5-0.84-6
2 PM40-604-1075 / 256WNW/5-15NaN4-8
Fri Oct 03 - 2 AM10-309.5-1060 / 152WSW/0-100.5-0.83-5
2 PM40-604-560 / 106W/5-15NaN4-8
Sat Oct 04 - 2 AM0-20Clear50 / 102WSW/0-100.4-0.83-5
2 PM40-604-540 / 106NW/5-15NaN3-6
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 Sep 29 - Tue Sep 30 18:20 19:25 4:59 6:04 N/A 22:39 34 17 11.9 -18 41
Tue Sep 30 - Wed Oct 01 18:20 19:24 5:00 6:04 N/A 23:35 45 18 08.9 -18 38
Wed Oct 01 - Thu Oct 02 18:19 19:23 5:00 6:04 N/A 0:33 56 19 07.0 -17 30
Thu Oct 02 - Fri Oct 03 18:18 19:22 5:00 6:04 N/A 1:33 67 20 05.5 -15 16
Fri Oct 03 - Sat Oct 04 18:17 19:21 5:00 6:05 N/A 2:34 78 21 03.8 -12 04
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 30 September 2014.
Additional Information
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