Current Conditions
Temp8.7 C
RH11 %
WindE 12 mph
RoadOpen
Mauna Kea Observatories Forecast
730 AM HST (1730 UTC) Tuesday 02 September 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 11 C this afternoon, 5.5 C this evening and 4.5 C tomorrow morning. Winds will be from the NNE at 10-20 mph, with seeing around 0.4-0.45 arcseconds. Precipitable water is expected to be in the 1.5-2 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture near 6-7 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 1.75 mm for tonight, briefly slip toward 1 mm for tomorrow night, then increase toward 1.5-2 mm for the Wednesday, Thursday and Friday night.

Relatively light winds at and above the summit combined with deep subsidence will help keep shear/turbulence in free atmosphere to a minimum and allow for good/excellent seeing for the next 3 nights. There is a possibility that minor upper-level turbulence will build into the area for Thursday and Friday night, but better than average seeing should still prevail.

The mid/low-level ridge will continue to sit to the north of the Island and promote steady/strong large-scale subsidence in the area probably well into next week. This will help maintain the tradewind inversion near 7 thousand feet and ensure the summit remains dry and stable throughout the forecast period. An upper-level ridge is also slated to linger overhead, which will augment the subsidence over the summit, keep high clouds at bay, minimize turbulence in the free atmosphere and likely allow for good/excellent seeing over the next 3 nights. This ridge is slated to breakdown as a weak tropical upper-tropospheric trough (TUTT) builds in to the northwest starting early Thursday morning. The TUTT is not expected to affect the stability of the atmosphere or gain access to any high clouds, but could increase turbulence in the free atmosphere and slightly degrade seeing for Thursday and Friday 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)
Tue Sep 02 - 2 PM0-20Clear0 / 011NNE/10-20NaN1.5-2.5
8 PM0-5Clear0 / 05.5NNE/10-200.4-0.51.5-2
Wed Sep 03 - 2 AM0-5Clear0 / 04.5NE/10-200.35-0.451.5-2
2 PM0-20Clear0 / 010NE/10-20NaN1-2
8 PM0-5Clear0 / 05NE/10-200.35-0.451-1.5
Thu Sep 04 - 2 AM0-5Clear0 / 04.5NE/5-150.35-0.451-1.5
2 PM0-20Clear0 / 09NE/5-15NaN1-2
8 PM0-5Clear0 / 04NE/0-100.35-0.451.5-2
Fri Sep 05 - 2 AM0-5Clear0 / 03.5NE/0-100.4-0.51.5-2
2 PM0-20Clear0 / 08.5E/0-10NaN1.5-2.5
Sat Sep 06 - 2 AM0-5Clear0 / 03ESE/0-100.4-0.61.5-2.5
2 PM0-20Clear0 / 08E/0-10NaN1.5-2.5
Sun Sep 07 - 2 AM0-5Clear0 / 03E/5-150.4-0.61.5-2.5
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
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
Sat Sep 06 - Sun Sep 07 18:41 19:47 4:54 5:59 N/A 4:51 96 21 27.7 -10 43
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Tuesday 02 September (0300 UTC Wednesday 3 September) 2014.
Additional Information
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This message is also available at the MKWC road conditions page.
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