Current Conditions
Temp4.0 C
RH40 %
WindSE 0 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
10 AM HST (2000 UTC) Thursday 01 December 2022
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 6 C this afternoon, 2 C this evening and 1.5 C tomorrow morning. Winds will be from the north at 10-20 mph, with seeing near 0.55-0.6 arcseconds. Precipitable water is expected to be in the 3-4 mm range for the first half of the night and 2-3 mm range for the second half.
Discussion
Although the inversion is set to strengthen and become quite well-defined, it will remain somewhat elevated near 10-11 thousand feet probably through the next 5 nights. This may allow for short-lived fog/high humidity, though the odds are slim due to the lack of low-level forcing during this time; precipitation is not expected. Some minor afternoon clouds are possible throughout the forecast period.

There is a possibility for isolated slow-moving high clouds spreading in from the west and passing over/near the summit area over the next 2 nights. After a brief break on Saturday morning, scattered to broken thicker high clouds will build in from the west and drift overhead for the remainder of the forecast period.

Precipitable water will start out near 4 mm for this evening, but will slip into the 2-3 mm range by the end of the night and for the following 2 nights. There is a good chance that PW will increase back into the 3-4 mm range for Sunday and Monday night.

While conditions are set to improve, a brief increase in low-level turbulence may contribute to more average-like seeing for tonight. Calm skies at and above the summit should allow seeing to settle in near 0.4-0.5 arcseconds for Friday and Saturday night. However, an increase in free atmospheric shear/turbulence may drive seeing back toward 0.6 arcseconds for the following 2 nights.

A deep ridge developing to the north of the state will help squash the residual moisture southward and reinstill large-scale subsidence in the area for the next several days. This subsidence will help re-strengthen the tradewind inversion, but there is a chance that a persistent upper-level trough to the NE will continue to enhance the incoming low-level cloud field into the weekend. This could keep the inversion fairly elevated near 10-11 thousand feet and may allow for short-lived fog/high humidity at the summit mainly through Saturday night. Still, the odds are very slim as low-level trades are set to become quite light, which will limit the forcing necessary to overcome the inversion. Nevertheless, an overall improvement in conditions should allow for seeing (and to some extent PW) to return to more normal values for tonight. Seeing may eventually settle in near 0.4-0.5 arcseconds as deep subsidence associated with the ridge builds in overhead, allowing calm skies to prevail at and above the summit for Friday and Saturday night. However, there is a chance that a branch of the westerly jet will develop overhead as an upper-level trough digs in far to the west late in the weekend. The jet will strengthen flow aloft, enhancing free atmospheric turbulence/shear and could contribute to slight degradation in seeing for Sunday and 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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Thu Dec 01 - 2 PM0-209-1040 / 06N/10-20NaN3-6
8 PM0-59.5-1020 / 02N/10-200.5-0.73-4
Fri Dec 02 - 2 AM0-59.5-1015 / 01.5N/10-200.5-0.72-3
2 PM0-209-9.530 / 07.5N/5-15NaN2-4
8 PM0-59-9.520 / 02.5N/5-150.35-0.552-3
Sat Dec 03 - 2 AM0-59-9.520 / 02N/5-150.35-0.552-3
2 PM0-208-1025 / 07NW/0-10NaN2-3
8 PM0-57-1020 / 02N/0-100.35-0.552-3
Sun Dec 04 - 2 AM0-57-1015 / 01.5N/0-100.4-0.62-3
2 PM0-207-1020 / 06.5W/0-10NaN2-4
Mon Dec 05 - 2 AM0-57-1010 / 01W/0-100.425-0.6753-4
2 PM0-207-1020 / 06.5SSE/0-10NaN3-5
Tue Dec 06 - 2 AM0-57-1010 / 01.5SSE/5-150.425-0.6753-4
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 Dec 01 - Fri Dec 02 17:51 18:59 5:23 6:31 N/A 2:03 69 0 13.1 -2 16
Fri Dec 02 - Sat Dec 03 17:51 19:00 5:24 6:32 N/A 2:57 78 1 00.5 3 53
Sat Dec 03 - Sun Dec 04 17:52 19:00 5:24 6:33 N/A 3:51 86 1 47.8 9 46
Sun Dec 04 - Mon Dec 05 17:52 19:00 5:25 6:33 N/A 4:45 92 2 36.1 15 10
Mon Dec 05 - Tue Dec 06 17:52 19:00 5:25 6:34 N/A 5:40 97 3 26.0 19 50
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Thursday 01 December (0300 UTC Friday 2 December) 2022.
Additional Information
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This message is also available at the MKWC road conditions page.
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