Current Conditions
Temp4.8 C
RH9 %
WindSSW 9 mph
RoadOpen (4x4 only)
Mauna Kea Observatories Forecast
5 PM HST Thursday 08 October (0300 UTC Friday 9 October) 2015
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 5.5 C this evening and 5 C tomorrow morning. Winds will be from the SSW at 5-15 mph, with seeing around 0.45-0.5 arcseconds. Precipitable water is expected to be in the 0.9-1.1 mm range for the night.
The tradewind inversion will continue to cap low-level moisture near 8 thousand feet and ensure a dry/stable summit-level air mass through at least tomorrow afternoon. There is a possibility that building instability to north, coupled with an influx of low-level tropical moisture will erode the inversion and increase the risk for periods of fog and high humidity at the summit over the weekend and into next week (some drying is possible for Sunday night). There is also a chance for afternoon convection along the slopes and light rain at the summit during that period. Daytime clouds will be minimal and short-lived for tomorrow, but could turn extensive over the weekend and early part of next week.

Skies will remain predominately clear for tonight, but there is a chance that thicker scattered/broken mid/upper-level clouds will start build in from the SE and/or develop in the area late Friday night and for the remainder of the forecast period. There is also a possibility that banding high clouds will set up over/near the summit area for the early part of next week.

Precipitable water is expected to dip toward 1 mm for tonight, then likely linger near or exceed 4 mm for the remainder of the forecast period.

Calm flow at and above the summit should allow for better than average seeing for tonight. An increase in low-level turbulence may start to degrade seeing for Friday and especially Saturday night. There is a chance for an improvement in seeing for Sunday night, but another increase in upper-level turbulence may affect seeing for Monday night.

No change since the morning forecast...The eastern tip of a relatively deep ridge filling in from the west, coupled with relatively zonal flow aloft will allow warm, dry and stable air to prevail in the area through at least tomorrow afternoon. Clear/calm skies will also persist in the area, which should allow for better than average seeing for another night. Unfortunately, the remnant trailing band of tropical moisture associated with departing extra-tropical storm Oho and large trough is slated to get caught up in the low-level trades and return to the summit area beginning late Friday evening. This moisture, combined with a building weak trough to the north could help to erode the inversion through that night, which will significantly increase the risk for fog and high humidity at the summit, particularly between early Saturday morning and around sunrise on Sunday. Isolated convection along the slopes and light rain at the summit are also possible mainly for Saturday afternoon. There is a chance that the air mass will dry out and stabilize a tad as this band of moisture shifts westward and a new ridge fills in from the ESE for Sunday night. However, the weak upper-level trough is expected to deepen and deposit a low just west of the state for the early part of next week. This low could further destabilize the air mass and increase the risk for fog/high humidity at the summit once again for Monday 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)
Thu Oct 08 - 8 PM0-5Clear0 / 05.5SSW/5-150.45-0.550.9-1.1
Fri Oct 09 - 2 AM0-5Clear0 / 05SW/5-150.4-0.50.9-1.1
2 PM0-20Clear0 / 010SSE/5-15NaN2-4
8 PM20-406-825 / 54.5S/10-200.5-0.73.5-4.5
Sat Oct 10 - 2 AM40-605-860 / 153.5SSW/10-200.6-0.94-8
2 PM60-804-890 / 607SSW/5-15NaN8-12
8 PM60-804.5-980 / 402.5ESE/5-150.7-1.38-12
Sun Oct 11 - 2 AM60-804.5-975 / 252E/5-150.7-1.38-12
2 PM50-704-775 / 308ENE/5-15NaN4-8
Mon Oct 12 - 2 AM40-605-740 / 103ENE/5-150.5-0.83-5
2 PM60-804-960 / 207N/0-10NaN4-8
Tue Oct 13 - 2 AM50-705-870 / 152.5SSE/5-150.5-1.16-10
2 PM0-204-1080 / 406SW/5-15NaN8-12
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 Oct 08 - Fri Oct 09 18:13 19:17 5:02 6:06 3:31 N/A 11 10 33.6 6 33
Fri Oct 09 - Sat Oct 10 18:12 19:16 5:02 6:06 4:19 N/A 6 11 18.5 3 03
Sat Oct 10 - Sun Oct 11 18:11 19:16 5:02 6:06 5:07 17:03 2 12 03.0 -0 34
Sun Oct 11 - Mon Oct 12 18:10 19:15 5:02 6:07 5:55 17:40 0 12 47.4 -4 11
Mon Oct 12 - Tue Oct 13 18:10 19:14 5:03 6:07 6:44 18:17 0 13 32.4 -7 39
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 9 October 2015.
Additional Information
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This message is also available at the MKWC road conditions page.
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