Current Conditions
Temp2.9 C
RH40 %
WindSW 1 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Wednesday 30 November (0300 UTC Thursday 1 December) 2022
Fog/ice and high humidity
Cloud Cover and Fog/Precipitation Forecast
There is a high risk for periods of fog, ice and high humidity throughout the night; precipitation is unlikely. Isolated to scattered deep clouds may linger in the area for this evening, but will continue to sag southward and dissipate through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 0 C, with winds from the NW at 5-15 mph for the night. Seeing and PW will exceed 1 arcsecond and 4 mm, respectively, throughout the night.
The atmosphere below 16 thousand feet will remain mostly saturated, which could allow for more fog, ice and high humidity to plague the summit for tonight; precipitation is unlikely. The lower air mass will begin to dry out late tomorrow morning as the inversion slowly rebuilds near 9-10 thousand feet, which will help reduce this risk for that night. A more well-defined inversion near 8-9 thousand feet will ensure dry and stable conditions for Friday, Saturday and Sunday night. Daytime clouds will taper for tomorrow, become minimal and short-lived through the weekend, but could pick up again early next week.

Isolated to scattered deep clouds will likely linger in the area for this evening, but will sag southward and dissipate as the night progresses. There is a chance for nearly transparent high clouds slow-moving high clouds persisting overhead for the next 2 nights. More scattered mid/upper-level are expected to fill in from the west, but are unlikely to push cloud cover beyond 30% for Saturday and Sunday night.

Precipitable water is expected to exceed 4 mm for tonight, but will slip toward 2-3 mm over the next 3 nights (there is a chance that it will dip below 2 mm for Friday night), only to rebound back to 3-4 mm for Saturday and Sunday night.

A fairly saturated air mass and indistinct/elevated inversion will likely contribute to bad seeing for tonight. There is a very good chance that seeing will improve with conditions by tomorrow night and should settle in near 0.4-0.45 arcseconds as relatively calm skies prevails overhead for Friday and Saturday night. An increase in free atmospheric turbulence may contribute to more average-like seeing for Sunday night.

Subtle changes have been made to the PW forecast...Although a deep tight ridge will begin to take shape just north of the state, residual deep low-level moisture will persist in the area through late tomorrow morning. This will prohibit the inversion from restrengthening and probably allow for more periods of fog, ice and high humidity at the summit for tonight. Eventually, the bulk of the moisture will shift southward as the ridge expands a bit by tomorrow evening, but there is still a possibility for brief fog/high humidity until more widespread subsidence returns and the inversion becomes more well-defined near 8-9 thousand feet around Friday morning. This will ensure the summit remains dry and stable through the weekend. In addition, there is a very good chance that seeing will dip toward 0.4-0.5 arcseconds as the upper portion of the ridge passes overhead and very calm skies prevails at and above the summit as early as Thursday night and especially for the following 2 nights. A new short-wave trough (SWT) building far to the NW, combined with another trough developing to the far east will help to form a rather strong sub-tropical jet overhead late in the weekend. This STJ will likely increase shear/turbulence in the free atmosphere and degrade seeing through that night. Long-term projections suggest that the SWT building to the NW will help develop another low to the NNE of the state early to middle part of next week. There is a chance that this low could bring another round of moisture/instability to the area, depending on where (and if) this low forms relative to the Big Island...
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)
Wed Nov 30 - 8 PM30-504-790 / 300NW/5-150.8-1.68-12
Thu Dec 01 - 2 AM10-304-565 / 150NW/5-150.7-1.34-8
2 PM40-604-4.550 / 106N/10-20NaN4-8
8 PM0-209.5-1030 / 02N/5-150.425-0.6753-4
Fri Dec 02 - 2 AM0-209.5-1020 / 01N/5-150.4-0.62.5-3.5
2 PM0-208.5-9.510 / 07.5N/5-15NaN2-4
8 PM0-208.5-90 / 02N/5-150.35-0.551.5-2.5
Sat Dec 03 - 2 AM0-208.5-90 / 01.5N/5-150.3-0.51.5-2.5
2 PM0-208.5-100 / 07W/5-15NaN2-4
Sun Dec 04 - 2 AM10-309-100 / 01.5WNW/0-100.3-0.52-3
2 PM10-308.5-100 / 06.5WNW/0-10NaN3-5
Mon Dec 05 - 2 AM10-308.5-100 / 00.5NW/0-100.4-0.83-5
2 PM0-20Clear0 / 06NE/5-15NaN4-6
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 10 AM HST (2000 UTC) Thursday 1 December 2022.
Additional Information
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