Current Conditions
Temp4.0 C
RH8 %
WindNNE 8 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Friday 24 June (0300 UTC Saturday 25 June) 2022
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable through the night. The summit sky will be predominantly clear but for some high scattered clouds visible along the western and southern sky.
Summary of Key Meteorological Variables
Summit temperatures will be near 3 C this evening and 2.5 C tomorrow morning. Winds will be light and from the NE, with seeing near 0.5-0.55 arcseconds. Precipitable water is expected to be in the 0.6-0.8 mm range for most of the night.
Discussion
A well established tradewind inversion will continue to cap low-level moisture below 8-9 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Isolated/scattered high clouds will be visible along the southwestern horizon. Some of them might actually stream overhead tonight. High clouds will get more organized through Saturday and are expected to interest the summit sky from Saturday evening/night and through part of Monday. A clearing trend is expected afterward.

Precipitable water will be in the 0.6-0.8 mm range tonight, trend toward 1 mm through Saturday night and perhaps into the 1-1.5 mm range for Sunday night. There is a good chance that it will decrease back to 1 mm or slightly less for Monday and Tuesday night.

Despite light/moderate shear in the free atmosphere, calm mid-level flow combined with a stable air mass should allow seeing to be average to better than average (near 0.5-0.55) arcseconds tonight and Saturday night. There is a possibility for minor degradation as the shear increases subtly during the weekend while returning to more average values from Monday and onward.

Subtle changes have been made to the PW forecast...The current weather scenario is dominated by a mid/surface ridge to the North of the State, which is expected to stretch across most of the Pacific through next week, and which subsidence will negate the effects of a well-defined tropical upper-tropospheric trough (TUTT) to the west. As a result the tradewind inversion will remain in place (8-9 thousand feet) and ensure a dry/stable summit-level air mass throughout the forecast period. On the other hand the Sub-Tropical Jet (STJ) is sending high clouds along the southern skies. These clouds are expected to mostly interest summit operations on Saturday night and through Sunday/Monday. Light/moderate shear associated with the STJ may also contribute to very minor degradation in seeing, particularly for Sunday night. There is a good chance that the shear will taper as the STJ lifts northward and dissipates, which could allow for an improvement in seeing for Monday and Tuesday 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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Fri Jun 24 - 8 PM0-20Clear0 / 08NE/0-100.45-0.650.6-0.8
Sat Jun 25 - 2 AM0-20Clear0 / 03NE/0-100.4-0.60.6-0.8
2 PM0-208-90 / 02.5ESE/0-10NaN0.8-1.2
8 PM10-307-90 / 08.5ESE/5-150.45-0.650.7-0.9
Sun Jun 26 - 2 AM30-506-80 / 03.5SE/5-150.525-0.7750.8-1
2 PM40-606-80 / 03.5SE/5-15NaN1-2
8 PM30-507-80 / 09SSE/5-150.525-0.7751-1.5
Mon Jun 27 - 2 AM20-407-80 / 04.5SE/5-150.5-0.71-1.5
2 PM10-308-90 / 04.5SE/5-15NaN1-2
Tue Jun 28 - 2 AM0-20Clear0 / 010ESE/5-150.45-0.650.8-1.2
2 PM0-20Clear0 / 05.5ESE/10-20NaN0.8-1.2
Wed Jun 29 - 2 AM0-20Clear0 / 010ENE/5-150.45-0.650.8-1.2
2 PM0-20Clear0 / 05.5E/10-20NaN1-2
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
Sat Jun 25 - Sun Jun 26 19:14 20:28 4:21 5:35 3:39 N/A 6 4 14.4 21 48
Sun Jun 26 - Mon Jun 27 19:14 20:28 4:22 5:36 4:23 17:38 3 5 04.5 24 24
Mon Jun 27 - Tue Jun 28 19:15 20:28 4:22 5:36 5:11 18:32 0 5 56.0 25 54
Tue Jun 28 - Wed Jun 29 19:15 20:29 4:22 5:36 6:01 19:23 0 6 48.2 26 13
Wed Jun 29 - Thu Jun 30 19:15 20:29 4:23 5:36 N/A 20:12 2 7 40.1 25 20
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 27 June 2022.
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.
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