Latest Forecast for Mauna Kea Observatories
10 AM HST (2000 UTC) Thursday 14 January 2021

Warnings
None

Cloud Cover and Precipitation Forecast
The summit will remain dry and stable, while isolated to scattered high clouds pass along the northern skies mainly during the first half of the night.

Summary of Key Meteorological Variables
Summit temperatures will be near 6 C this afternoon and 0.5 C for the night. Winds will be from the east at 5-15 mph for today, easing and switching to a more SSE direction through the night. Seeing will be near 0.5-0.6 arcseconds, while precipitable water is expected to be in the 2.5-3.5 mm range for the night.

Graphical Summary

Discussion
A fairly well-defined inversion will continue to cap low-level moisture near 7 thousand feet and ensure the summit remains dry and stable through at least Saturday night. Building instability will begin to erode the inversion and increase the risk for fog, ice and flurries at the summit through Sunday night and especially for Monday evening. Daytime clouds will be mimimal and short-lived through Saturday, but could pick up on Sunday, turn very extensive with the possibility for thunderstorms on Monday, then taper again through Tuesday.

THere is a chance for isolated to scattered high clouds passing along the northern skies for this evening. These clouds will shift eastward thereafter, leaving predominately clear skies through Sunday evening. Patches of mid/summit-level clouds may fill in from the WNW early Monday morning and may contribute to periods of extensive cloud cover (particularly along the northern half of the sky) before passing eastward through Tuesday.

Precipitable water is expected to slip into the 2-3 mm range for tonight, trend toward 1 mm through Friday night, increase back to 2-3 mm for Saturday night, and probably 3-4 mm through Sunday night and 4+ mm for Monday night.

Easing winds above the summit, combined with a drier more stable air mass will allow seeing to improve toward 0.5-0.6 arcseconds for tonight. There is a chance for a brief increase in winds, which could stir up boundary layer turbulence and contribute to a degradation in seeing for tomorrow evening. Seeing is set to improve again as winds subside through that night and eventually settle in near 0.5 arcseconds as relatively light/laminar northerly flow prevails in the free atmosphere for Saturday night. However, an increase in instability, boundary layer turbulence and the possibility for moisture and an elevated inversion will likely result in poor/bad seeing for Sunday and Monday night.



Astronomical Observing Quality Guidance
Seeing/CN2 Images are not available today. Sorry for the inconvenience.
Latest WRF CN2 Profiles Animation | Collage


5-day Forecast
Summary

Graphical Trend
02 pm HST
Thu 14 Jan
08 pm HST
Thu 14 Jan
02 am HST
Fri 15 Jan
02 pm HST
Fri 15 Jan
08 pm HST
Fri 15 Jan
02 am HST
Sat 16 Jan
02 pm HST
Sat 16 Jan
08 pm HST
Sat 16 Jan
02 am HST
Sun 17 Jan
02 pm HST
Sun 17 Jan
02 am HST
Mon 18 Jan
02 pm HST
Mon 18 Jan
02 am HST
Tue 19 Jan
00 UTC
Fri 15 Jan
06 UTC
Fri 15 Jan
12 UTC
Fri 15 Jan
00 UTC
Sat 16 Jan
06 UTC
Sat 16 Jan
12 UTC
Sat 16 Jan
00 UTC
Sun 17 Jan
06 UTC
Sun 17 Jan
12 UTC
Sun 17 Jan
00 UTC
Mon 18 Jan
12 UTC
Mon 18 Jan
00 UTC
Tue 19 Jan
12 UTC
Tue 19 Jan
Cloud Cover (%) 10 to 30 0 to 20 0 to 10 0 to 20 0 to 5 0 to 5 0 to 20 0 to 5 0 to 5 0 to 20 20 to 40 60 to 80 20 to 40
Cloud Height (km) above sea level 8-9 8-9 N/A N/A N/A N/A N/A N/A N/A N/A 4-5 4-8 4-6
Chance for Fog/Precip (%) 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 10/0 40/10 90/60 65/20
PW (mm, summit upward) 3 to 5 2 to 3 2 to 3 2 to 4 1.5 to 2 1 to 1.5 1.5 to 2.5 2 to 3 2 to 3 2 to 4 3 to 4 4 to 8 4 to 6
Mean Seeing (arcsecs) N/A 0.6 ± 0.1 0.5 ± 0.1 N/A 0.65 ± 0.15 0.55 ± 0.1 N/A 0.5 ± 0.1 0.5 ± 0.1 N/A 0.9 ± 0.2 N/A 1.2 ± 0.4
Summit Temp (°C) 6 0.5 0.5 6.5 1 1 6.5 1.5 1 4 -3 0 -4
Wind Dir/Speed (mph)
    Summit (615 hPa)
    19,000 ft (500 hPa)
    24,500 ft (400 hPa)
    31,000 ft (300 hPa)
    35,000 ft (250 hPa)
    40,000 ft (200 hPa)
    46,000 ft (150 hPa)
    54,000 ft (100 hPa)

E/5 to 15

ESE/5 to 15

SSE/0 to 10

NNE/10 to 20

NE/15 to 25

ENE/10 to 20

ESE/5 to 15

SE/5 to 15

SSE/10 to 20

SSW/15 to 30

SSW/20 to 35

SSW/25 to 40

NW/15 to 30


 Rise and Set times for the Sun and Moon
Night (HST)
Sun Set
Twilight End
Twilight Beg
Sun Rise
Moon Rise
Moon Set
Illum (%)
RA
Dec
Thu.Jan.14/Fri.Jan.15
18:13
19:20
5:42
6:50
N/A
20:03
6
21 46.6
-18 14
Fri.Jan.15/Sat.Jan.16
18:13
19:21
5:42
6:50
N/A
20:59
11
22 37.3
-14 02
Sat.Jan.16/Sun.Jan.17
18:14
19:22
5:42
6:50
N/A
21:53
18
23 25.0
-9 19
Sun.Jan.17/Mon.Jan.18
18:15
19:22
5:42
6:50
N/A
22:43
27
0 10.2
-4 20
Mon.Jan.18/Tue.Jan.19
18:15
19:23
5:42
6:50
N/A
23:32
36
0 54.1
0 43


Forecast issued by: Ryan Lyman
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Next update at 5 PM HST Thursday 14 January (0300 UTC Friday 15 January) 2021.
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