Current Conditions
Temp-0.9 C
RH28 %
WindW 18 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Friday 14 January (0300 UTC Saturday 15 January) 2022
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while scattered high clouds pass along the northern skies mainly through this evening.
Summary of Key Meteorological Variables
Summit temperatures will be near 1.5 C this evening and 0.5 C tomorrow morning. Winds will be from the WNW at 10-20 mph, while seeing will be near 0.7-0.8 arcseconds for the night. Precipitable water is expected to be in the 1.5-2 mm range for the first half of the night and 2-3 mm range for the second half.
Discussion
A well-defined tradewind inversion will continue to cap low-level moisture near 6-7 thousand feet and ensure a dry/stable summit-level air mass for tonight. There is a chance that the inversion will become more indistinct near 10-12 thousand feet, which could allow for short-lived fog and high humidity at the summit for Saturday and Sunday night; precipitation is not expected. The inversion is set to strengthen a tad, while moisture becomes harder to come by beginning Monday, which should ensure dry/stable conditions again for that night and Tuesday night. Daytime clouds may pick up over the weekend, then taper for the early part of next week.

Scattered high clouds are set to pass along the northern skies and occasionally over the summit area for the next 2 nights. These clouds will shift eastward on Saturday, leaving mostly clear skies for the remainder of the forecast period.

Precipitable water is expected to start out near 1.5 mm for this evening, but will trend toward 3 mm by the end of the night, and increase into the 3-4 mm range for Saturday and Sunday night. There is a good chance that it will slip back toward 2-3 mm for the early part of next week.

Residual mid-level thermodynamic turbulence combined with building shear in the free atmosphere will likely contribute to poorer than average seeing for tonight. The latter is set to strengthen further, while instability also fills into the area and light/moderate boundary layer turbulence increases through tomorrow. This will likely contribute to a further degradation in seeing over the weekend. While relatively strong shear will persist in the free atmosphere, there is a possibility for a modest improvement in seeing as the inversion strengthens and the boundary layer turbulence subsides for Monday night. Another round of light boundary layer turbulence may deteriorate seeing again for Tuesday night.

Little change since the morning forecast....The mid/surface ridge will continue to sit over or just north of the Big Island and continue to promote strong large-scale subsidence in the area through at least late tomorrow morning. This subsidence will help maintain a well-defined inversion primarily near 6-7 thousand feet and ensure a dry/stable summit-level air mass for tonight. While predominately laminar westerly flow will prevail in the free atmosphere as a relatively zonal (albeit robust) westerly jet sits to the NW, cold mid/upper-level air (turbulence) and high clouds associated with a passing trough/low will slip by to the north through the night. The cold pool of air will likely create more free atmospheric turbulence and contribute to poor seeing for tonight. The clouds and turbulence will slip eastward as a short-wave trough digs in from the north and helps develop a larger trough to the SE on Saturday. Unfortunately, in the process the trough will displace the ridge to the SW and bring colder upper-level air into the area over the weekend and early part of next week. This could destabilize the air mass thermodynamically, which may weaken the inversion and increase the risk for short-lived fog, high humidity and daytime clouds at the summit during that time (though the odds are low). This instability, combined with strong northerly upper-level flow and an increase in summit-level winds may further degrade seeing for much of the weekend. Models do suggest that the ridge will return from the SW and build back over the Islands beginning Monday. This should help expunge the residual moisture eastward, restabilize the air mass and ensure the summit steers free of fog/precipitation for the early part of next week. The upper-level shear/turbulence may still persist overhead, prohibiting much improvement in seeing through Tuesday night.

Please Note: There will be no forecasts on Monday, Jan 17, in observance of Martin Luther King Day. The normal forecast schedule will resume on Tuesday Jan 18.
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 Jan 14 - 8 PM10-308-90 / 01.5WNW/10-200.575-0.8251.5-2
Sat Jan 15 - 2 AM0-208-90 / 00.5WNW/10-200.675-0.9252-3
2 PM20-404-4.530 / 103.5NW/15-25NaN3-5
8 PM0-10Clear40 / 0-1NW/15-250.8-1.23-4
Sun Jan 16 - 2 AM0-10Clear30 / 00NW/15-250.7-1.13-4
2 PM40-604-540 / 153.5NW/10-20NaN4-6
8 PM0-5Clear20 / 0-0.5NNW/10-200.7-1.13-4
Mon Jan 17 - 2 AM0-5Clear10 / 0-0.5NNW/10-200.6-13-4
2 PM20-404-4.2520 / 55.5NNW/5-15NaN3-5
Tue Jan 18 - 2 AM0-5Clear0 / 00.5NW/5-150.55-0.852-3
2 PM0-20Clear10 / 05NW/5-15NaN2-3
Wed Jan 19 - 2 AM0-5Clear0 / 0-1WNW/10-200.6-11.5-2.5
2 PM0-20Clear0 / 03NNW/10-20NaN2-4
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
Sat Jan 15 - Sun Jan 16 18:13 19:21 5:42 6:50 N/A 6:22 98 6 38.8 26 24
Sun Jan 16 - Mon Jan 17 18:14 19:21 5:42 6:50 17:03 7:11 100 7 33.0 25 48
Mon Jan 17 - Tue Jan 18 18:14 19:22 5:42 6:50 17:57 N/A 100 8 26.8 23 56
Tue Jan 18 - Wed Jan 19 18:15 19:23 5:42 6:50 18:52 N/A 98 9 19.2 20 53
Wed Jan 19 - Thu Jan 20 18:16 19:23 5:43 6:50 19:47 N/A 94 10 09.8 16 51
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 17 January 2022.
Additional Information
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