Latest Forecast for Maunakea Observatories
10 AM HST (2000 UTC) Monday 27 June 2022

Warnings
None

Cloud Cover and Precipitation Forecast
The summit will remain dry and stable, but there is a possibility for scattered thin cirrus in the area, particularly along the northern skies, through the night.

Summary of Key Meteorological Variables
Summit temperatures will be near 10 C this afternoon and 5 C for the night. Winds will be from the ESE at 5-15 mph, with seeing near 0.5 arcseconds. Precipitable water is expected to be near 0.7-0.8 mm for the night.

Graphical Summary

Discussion
A distinct tradewind inversion will continue to cap low-level moisture near 8-9 thousand feet and ensure a dry and stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived through Friday, but could pick up over the weekend.

Scattered thin high clouds will continue to fill in from the SW, but will move to the northern skies for tonight and to the western skies for the next several nights. Still cloud cover should not exceed 30% for any prolong periods throughout the forecast period.

Precipitable water is expected to linger near 0.7-0.8 mm for the next 3 nights, but could increase to 1+ mm through Thursday night and trend toward 2 mm through Friday night.

Calm/stable skies with relatively light/laminar flow will prevail at and above the summit, which should allow for better than average seeing for tonight and probably early tomorrow evening. A gradually increase in boundary layer turbulence could begin to degrade seeing during the latter night and will probably contribute to poor/bad seeing for Wednesday, Thursday and Friday night.

The mid/surface ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area into the early part of the weekend. This subsidence will easily negate the effects of the tropical upper-tropospheric to the west, maintain a well-defined inversion near 8-9 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. The TUTT is actually expected to shift further westward, which could allow a weak upper-level ridge to develop to the east after tonight. The sub-tropical jet along the southern flank of the TUTT, will also slip off toward the west and take on a more zonal orientation, limiting the any organized cirrus flowing out of the tropics and into the area and minimizing free atmospheric turbulence overhead. While this should allow for better than average seeing for at least tonight, summit-level winds are set to subtly pick up as the mid-level strengthens and expands to the north beginning early tomorrow night. A tropical wave/disturbance is also expected to fill in from the east on Thursday, and could significantly tighten the wind gradient and contribute to an abrupt increase in summit-level winds beween early Thursday evening and midnight Friday. Regardless, this increase in winds will strengthen boundary layer/low-level turbulence and probably result in poor/bad seeing for Wednesday, Thursday and Friday 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
Mon 27 Jun
08 pm HST
Mon 27 Jun
02 am HST
Tue 28 Jun
02 pm HST
Tue 28 Jun
08 pm HST
Tue 28 Jun
02 am HST
Wed 29 Jun
02 pm HST
Wed 29 Jun
08 pm HST
Wed 29 Jun
02 am HST
Thu 30 Jun
02 pm HST
Thu 30 Jun
02 am HST
Fri 01 Jul
02 pm HST
Fri 01 Jul
02 am HST
Sat 02 Jul
00 UTC
Tue 28 Jun
06 UTC
Tue 28 Jun
12 UTC
Tue 28 Jun
00 UTC
Wed 29 Jun
06 UTC
Wed 29 Jun
12 UTC
Wed 29 Jun
00 UTC
Thu 30 Jun
06 UTC
Thu 30 Jun
12 UTC
Thu 30 Jun
00 UTC
Fri 01 Jul
12 UTC
Fri 01 Jul
00 UTC
Sat 02 Jul
12 UTC
Sat 02 Jul
Cloud Cover (%) 10 to 30 0 to 20 0 to 20 0 to 20 10 to 30 10 to 30 10 to 30 0 to 20 10 to 30 0 to 20 10 to 30 10 to 30 10 to 30
Cloud Height (km) above sea level 9-10 9.5-10 9.5-10 N/A 9.5-10 9.5-10 9.5-10 9.5-10 9.5-10 9.5-10 9.5-10 9.5-10 9.5-10
Chance for Fog/Precip (%) 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0
PW (mm, summit upward) 0.8 to 1.2 0.7 to 0.9 0.6 to 0.8 0.8 to 1.2 0.7 to 0.9 0.7 to 0.9 0.8 to 1.2 0.6 to 0.8 0.7 to 0.9 1 to 1.5 0.8 to 1.2 1 to 1.5 1 to 2
Mean Seeing (arcsecs) N/A 0.5 ± 0.1 0.5 ± 0.1 N/A 0.6 ± 0.1 0.65 ± 0.15 N/A 0.8 ± 0.2 0.9 ± 0.2 N/A 1.2 ± 0.4 N/A 1.0 ± 0.3
Summit Temp (°C) 10 5 5 10.5 5.5 5.5 10 5.5 4.5 8 2 7 0
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)

ESE/5 to 15

ESE/5 to 15

E/5 to 15

ESE/10 to 20

E/10 to 20

ENE/10 to 20

E/15 to 30

E/15 to 30

ESE/15 to 30

E/15 to 30

E/25 to 40

ENE/20 to 35

ENE/20 to 35


 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
Mon.Jun.27/Tue.Jun.28
19:15
20:28
4:22
5:36
5:11
18:32
0
5 56.0
25 54
Tue.Jun.28/Wed.Jun.29
19:15
20:29
4:22
5:36
6:01
19:23
0
6 48.2
26 13
Wed.Jun.29/Thu.Jun.30
19:15
20:29
4:23
5:36
N/A
20:12
2
7 40.1
25 20
Thu.Jun.30/Fri.Jul.01
19:15
20:29
4:23
5:37
N/A
20:58
5
8 31.0
23 17
Fri.Jul.01/Sat.Jul.02
19:15
20:29
4:23
5:37
N/A
21:40
10
9 20.3
20 13


Forecast issued by: Ryan Lyman
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Next update at 5 PM HST Monday 27 June (0300 UTC Tuesday 28 June) 2022.
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