Current Conditions
Temp8.8 C
RH9 %
WindSE 1 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Friday 29 August (0300 UTC Saturday 30 August) 2014
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 7 C this evening and 7.5 C tomorrow morning. Winds will be from the NNW at 5-15 mph, with seeing around 0.35-0.4 arcseconds. Precipitable water is expected to be in the 1.25-1.75 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 9 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.

Summit skies will remain predominately clear through the next 5 nights.

Precipitable water is expected to linger near 1.5-1.75 mm for the next 4 nights, but may jump toward 2.5 mm for Tuesday night.

Deep strong subsidence, combined with light winds and minimal turbulence at and above the summit should allow for good/excellent seeing through the next 5 nights.

No change since the morning forecast...The mid/low-level ridge will continue to sit to the north of the Islands, while an upper-level ridge lingers over or just south of the Big Island through the long weekend. This will allow very strong/steady large-scale subsidence to prevail in the area, which will help maintain a well-defined tradewind inversion at or below 9 thousand feet and ensure a dry/stable and clear summit air mass through the next 5 nights (low-level remnants of an old tropical cyclone is slated to pass through the area, but will not be able to overcome the deep subsidence). The extra subsidence provided by the upper-level ridge will significantly warm the summit temperatures particularly over the next 3 nights and should also keep shear/turbulence in the free atmosphere to a minimum and allow for good/excellent seeing throughout the forecast period. There is a possibility that seeing will dip toward 0.3 arcseconds, particularly as the upper-level ridge settles in overhead between later tonight and early Sunday evening.

Please Note: There will be no normal forecasts on Monday, September 2, in observance of Labor Day. I will try to issue a brief update on Sunday or Monday, and the normal forecast schedule will resume on Tuesday.
HST CC (%) CLD HGT (km) Fog Prob (%) Prcp Prob (%) Temp (C) Wind (dir/mph) Seeing (asec) PW (mm)
---------------------------------------------------------------------------------------------------------------------------------------
08/29/2014 2000 0-5 Clear 0 0 7 330/5-15 0.35-0.45 1.25-1.75
08/30/2014 0200 0-5 Clear 0 0 7.5 330/5-15 0.3-0.4 1.25-1.75
08/30/2014 1400 0-20 Clear 0 0 12.5 270/0-10 NaN 1.25-1.75
08/30/2014 2000 0-5 Clear 0 0 7.5 300/0-10 0.3-0.4 1.25-1.75
08/31/2014 0200 0-5 Clear 0 0 7 315/0-10 0.3-0.4 1.5-2
08/31/2014 1400 0-20 Clear 0 0 12 45/0-10 NaN 1.5-2
08/31/2014 2000 0-5 Clear 0 0 7 45/0-10 0.3-0.4 1.5-2
09/01/2014 0200 0-5 Clear 0 0 6 30/0-10 0.35-0.45 1.5-2
09/01/2014 1400 0-20 Clear 0 0 11 45/5-15 NaN 1.25-1.75
09/02/2014 0200 0-5 Clear 0 0 6 45/5-15 0.35-0.55 1.25-1.75
09/02/2014 1400 0-20 Clear 0 0 11 45/5-15 NaN 2-3
09/03/2014 0200 0-5 Clear 0 0 5 45/10-20 0.3-0.5 2-3
09/03/2014 1400 0-20 Clear 0 0 10 30/10-20 NaN 2.5-3.5
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 Aug 29 - 8 PM0-5Clear0 / 07NNW/5-150.35-0.451.25-1.75
Sat Aug 30 - 2 AM0-5Clear0 / 07.5NNW/5-150.3-0.41.25-1.75
2 PM0-20Clear0 / 012.5W/0-10NaN1.25-1.75
8 PM0-5Clear0 / 07.5WNW/0-100.3-0.41.25-1.75
Sun Aug 31 - 2 AM0-5Clear0 / 07NW/0-100.3-0.41.5-2
2 PM0-20Clear0 / 012NE/0-10NaN1.5-2
8 PM0-5Clear0 / 07NE/0-100.3-0.41.5-2
Mon Sep 01 - 2 AM0-5Clear0 / 06NNE/0-100.35-0.451.5-2
2 PM0-20Clear0 / 011NE/5-15NaN1.25-1.75
Tue Sep 02 - 2 AM0-5Clear0 / 06NE/5-150.35-0.551.25-1.75
2 PM0-20Clear0 / 011NE/5-15NaN2-3
Wed Sep 03 - 2 AM0-5Clear0 / 05NE/10-200.3-0.52-3
2 PM0-20Clear0 / 010NNE/10-20NaN2.5-3.5
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 01 - Tue Sep 02 18:46 19:51 4:52 5:58 N/A 23:50 49 16 29.0 -18 16
Tue Sep 02 - Wed Sep 03 18:45 19:50 4:52 5:58 N/A 0:45 60 17 26.3 -19 01
Wed Sep 03 - Thu Sep 04 18:44 19:50 4:53 5:58 N/A 1:43 71 18 25.7 -18 40
Thu Sep 04 - Fri Sep 05 18:43 19:49 4:53 5:58 N/A 2:44 81 19 26.3 -17 08
Fri Sep 05 - Sat Sep 06 18:42 19:48 4:53 5:59 N/A 3:47 89 20 27.2 -14 25
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 1 September 2014.
Additional Information
For public road conditions and snow report message please call (808) 935-6268.
This message is also available at the MKWC road conditions page.
NWS Hawaiian Islands Synoptic Discussion and Guidance
Honolulu National Weather Service Data and Products