Maunakea Weather Center

Maunakea Observatories Forecast
5 PM HST Friday 09 June (0300 UTC Saturday 10 June) 2023
Moderate winds

Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while scattered high clouds continue to fill in from the SW and dissipate over/near the summit through the night.

Summary of Key Meteorological Variables
Summit temperatures will be near 5 C this evening and 4.5 C tomorrow morning. Winds will be from the east at 20-35 mph for today, easing a bit as the night progresses. Seeing will be near 1 arcsecond, while precipitable water is expected to linger in the 2-2.5 mm range for the night.

A well-defined inversion will continue to cap low-level moisture at or below 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.

Scattered high clouds will continue to fill in from the SW and dissipate over/near the summit for tonight. There is a good chance for a break in these clouds for Saturday nihgt, but more patches of high clouds may build along the western skies again on Sunday. These clouds will likely fill in overhead for that night then slowly dissipate in the area for the early part of next week.

Precipitable water is expected to settle in near 2-2.5 mm for tonight, increase to 4+ mm for the next 2 nights, then slip back toward 2-2.5 mm for Monday and Tuesday night.

Despite relatively light flow in the free atmosphere, boundary/low-level turbulence will contribute to poor seeing for at least the next 2 nights. A modest improvement in seeing is possible as winds taper a bit for Sunday and Monday night, with better than average seeing likely return as winds continue to subside for Tuesday night.

No change since the morning forecast...A relatively deep mid/surface ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area probably well into next week. This subsidence will easily maintain a well-defined inversion at or below 9 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. A very weak tropical upper-tropospheric trough (TUTT) will still persist in the area, before re-strengthening overhead middle/later part of next week. While the TUTT will have no impact on the stability of the atmosphere during its immediate tenure, an embedded upper-level low to the west of the state could send patches of dissipating isolated high clouds into the area for tonight. There is a good chance that high clouds will rotate to the north of the low, clearing up skies for tomorrow night. The low is expected to drift over the Big Island, then stall and gradually strengthen, bringing more patches of high clouds to the area for Sunday and early part of next week. Still, mostly calm skies wil prevail in the free atmosphere, as the sub-tropical jet remainds displaced to south throughout the forecast period. However, the expansion and subtle strengthening of the mid-level ridge to the north will result in an increase in boundary/low-level turbulence probably through the weekend and probably into Monday evening. This will contribute to poorer than average seeing over much of the next 4 nights, but there is a good chance that winds will subside as the ridge lifts further off toward the NE in response to the strengthening of the upper-level low on Tuesday.
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 09 - 8 PM10-309-100 / 05E/20-350.7-1.32-2.5
Sat Jun 10 - 2 AM0-209-100 / 04.5E/15-250.7-1.32-2.5
2 PM0-20Clear0 / 09E/15-25NaN3-5
8 PM0-10Clear0 / 03.5E/15-250.7-1.14-6
Sun Jun 11 - 2 AM0-10Clear0 / 03E/15-250.6-14-6
2 PM0-20Clear0 / 08.5E/15-25NaN4-6
8 PM0-208.5-90 / 03E/15-250.55-0.853.5-4.5
Mon Jun 12 - 2 AM10-308.5-90 / 02.5E/15-250.5-0.83.5-4.5
2 PM0-208-90 / 07.5E/15-25NaN3-5
Tue Jun 13 - 2 AM0-208-90 / 02E/10-200.5-0.82-3
2 PM0-208-90 / 07E/5-15NaN2-3
Wed Jun 14 - 2 AM0-208.5-90 / 02ESE/0-100.425-0.6751.5-2.5
2 PM0-208.5-90 / 07SE/0-10NaN1.5-2.5
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
Fri Jun 09 - Sat Jun 10 19:10 20:24 4:19 5:32 0:22 N/A 54 23 11.2 -10 09
Sat Jun 10 - Sun Jun 11 19:10 20:24 4:19 5:32 1:00 N/A 43 0 01.2 -3 47
Sun Jun 11 - Mon Jun 12 19:11 20:25 4:19 5:33 1:36 N/A 32 0 49.6 2 36
Mon Jun 12 - Tue Jun 13 19:11 20:25 4:19 5:33 2:12 N/A 22 1 37.6 8 43
Tue Jun 13 - Wed Jun 14 19:11 20:25 4:19 5:33 2:50 N/A 14 2 26.3 14 20
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 12 June 2023.
Additional Information
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