Latest Forecast for Mauna Kea Observatories
7 AM HST (1700 UTC) Thursday 10 January 2019

Warnings
None

Cloud Cover and Precipitation Forecast
The summit will remain clear, dry and stable through the night.

Summary of Key Meteorological Variables
Summit temperatures will be near 9 C this afternoon, 4.5 C this evening and 4 C tomorrow morning. Winds will be from the north at 5-15 mph for today, switching to a more NE direction through the night. Seeing will be near 0.4-0.45 arcseconds, while precipitable water is expected to be in the 1-1.5 mm range for the night.

Graphical Summary

Discussion
A strong well-defined tradewind inversion will continue to cap low-level moisture at or below 8 thousand feet and ensure the summit remains dry and stable through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Skies will remain predominately clear through the next 5 nights.

Precipitable water is expected to increase toward 1.2-1.4 mm for tonight, slip back toward 1 mm through Friday night, then dip toward 0.7-0.9 mm for the following 3 nights.

Very calm/stable skies with relatively laminar north to northwesterly flow will prevail in the free atmosphere, which should allow seeing to settle in near 0.4-0.45 arcseconds probably throughout the forecast period.

A fairly deep mid/low-level ridge will continue to sit almost directly over or just north of the Big Island and promote steady/strong large-scale subsidence in the area well into next week. This subsidence will help maintain a well-defined inversion near 7-8 thousand feet and ensure the summit remains dry/stable and relatively warm through the next 5 nights. Skies will also remain predominately clear as a zonal westerly jet well north of the state continues to shuttle high clouds away from the area during this time. This should also allow relatively weak/laminar northwesterly flow to prevail aloft, minimizing turbulence in the free atmosphere during this time. Weak (not dead) winds at the summit should also promote some sort of mixing at the summit, which should allow seeing to settle in near 0.4-0.5 arcseconds probably for the remainder of the week and into next week. PW, on the other hand, may spike toward 1.5 mm as a patch of mid-level moisture passes through for tonight. However, the deep subsidence in the area should help PW drive toward 1 mm by tomorrow night and 0.8 mm for the following 3 nights.

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 10 Jan
08 pm HST
Thu 10 Jan
02 am HST
Fri 11 Jan
02 pm HST
Fri 11 Jan
08 pm HST
Fri 11 Jan
02 am HST
Sat 12 Jan
02 pm HST
Sat 12 Jan
08 pm HST
Sat 12 Jan
02 am HST
Sun 13 Jan
02 pm HST
Sun 13 Jan
02 am HST
Mon 14 Jan
02 pm HST
Mon 14 Jan
02 am HST
Tue 15 Jan
00 UTC
Fri 11 Jan
06 UTC
Fri 11 Jan
12 UTC
Fri 11 Jan
00 UTC
Sat 12 Jan
06 UTC
Sat 12 Jan
12 UTC
Sat 12 Jan
00 UTC
Sun 13 Jan
06 UTC
Sun 13 Jan
12 UTC
Sun 13 Jan
00 UTC
Mon 14 Jan
12 UTC
Mon 14 Jan
00 UTC
Tue 15 Jan
12 UTC
Tue 15 Jan
Cloud Cover (%) 0 to 20 0 to 5 0 to 5 0 to 20 0 to 5 0 to 5 0 to 20 0 to 5 0 to 5 0 to 20 0 to 5 0 to 20 0 to 5
Cloud Height (km) above sea level N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
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) 1 to 1.5 1 to 1.5 1 to 1.5 1 to 1.5 1 to 1.2 0.9 to 1.1 1 to 1.5 0.8 to 1 0.8 to 1 0.8 to 1.2 0.6 to 1 0.8 to 1.2 0.6 to 1
Mean Seeing (arcsecs) N/A 0.45 ± 0.1 0.4 ± 0.1 N/A 0.4 ± 0.1 0.4 ± 0.1 N/A 0.45 ± 0.1 0.4 ± 0.1 N/A 0.45 ± 0.1 N/A 0.5 ± 0.1
Summit Temp (°C) 9 4.5 4 9 4.5 4 9 4 3.5 8.5 3 8.5 3
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)

N/5 to 15

NNE/5 to 15

NE/5 to 15

NE/5 to 15

ENE/5 to 15

E/5 to 15

SE/5 to 15

ESE/5 to 15

E/0 to 10

NNE/5 to 15

NNE/5 to 15

N/5 to 15

NNW/10 to 20


 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.10/Fri.Jan.11
18:10
19:18
5:41
6:49
N/A
22:18
23
23 22.6
-8 30
Fri.Jan.11/Sat.Jan.12
18:10
19:19
5:42
6:50
N/A
23:07
31
0 07.4
-4 19
Sat.Jan.12/Sun.Jan.13
18:11
19:19
5:42
6:50
N/A
23:56
41
0 52.6
0 06
Sun.Jan.13/Mon.Jan.14
18:12
19:20
5:42
6:50
N/A
0:47
51
1 38.8
4 37
Mon.Jan.14/Tue.Jan.15
18:12
19:20
5:42
6:50
N/A
1:40
61
2 27.1
9 05


Forecast issued by: Ryan Lyman
Contact Us - (808) 932-2323
Hours: Mon-Fri 8 AM - 5 PM HST (1800-0300 UTC)

For public road conditions and snow report message please call (808) 935-6268.
This message is also available at the MKWC road conditions page.

Next update at 5 PM HST Thursday 10 January (0300 UTC Friday 11 January) 2019.
Please call or email to be placed on the Mauna Kea Weather Bulletin email list.