Latest Forecast for Mauna Kea Observatories
10 AM HST (2000 UTC) Thursday 08 November 2018

Warnings
Chance for fog
Possibility for afternoon convection

Cloud Cover and Precipitation Forecast
There is a moderate risk for fog and high humidity throughout the night; precipitation is unlikely. Patches of mid-level clouds may also pass along the SE and eastern skies through the night.

Summary of Key Meteorological Variables
Summit temperatures will be near 6 C this afternoon, 2 C this evening and 1 C tomorrow morning. Winds will be from the SSW at 10-20 mph for today and 15-30 mph for the night.

Graphical Summary

Discussion
While there is a possibility that the tradewind inversion will strengthen through the night, mid/low-level moisture passing through/near the area may contribute to periods of fog and high humidity through the night. There is a very good chance that the inversion will breakdown again through Friday night, allowing the atmosphere to turn quite saturated for Saturday night. This will raise the stakes on extensive fog, ice, high humidity and light flurries at the summit durign those nights, particularly the latter. The inversion is set to rapidly recover through Sunday, becoming well-defined near 6 thousand feet and ensure a dry/stable summit-level air mass for that night as well as Monday night. Some afternoon clouds are likely through tomorrow, then will turn extensive for Saturday, only to become minimal and short-lived for the following 2 days.

There is a possibility that patches of mid-level clouds passing along the SE and eastern skies will be visible from the summit through the night. These clouds may creep closer to the Big Island, as thicker clouds build over and drift in from the NW, which will likely contribute to extensive cloud cover for Friday night and mostly overcast skies for Saturday night. All of these clouds are set to shift off toward the east near sunrise Sunday, but may still continue to scrape the SE coast of the Big Island before shifting further eastward early Monday morning, leaving predominately clear skies for that night.

Precipitable water is expected to linger near or exceed 4 mm for the next 3 nights, then plummet toward 0.7-0.8 mm for Sunday and probably Monday night.

A mixture of boundary layer turbulence, mid-level turbulence, an elevated/weak inversion and/or a saturated air mass will contribute to poor/bad seeing for at least the next 3 nights. The air mass is expected to dry out and stabilize on Sunday, but lingering boundary layer/low-level turbulence may still limit much improvement in seeing for that night. Calmer skies should allow seeing to settle in near 0.5-0.6 arcseconds for Monday night.

The developing low to the NNW of the state will continue to drag mid-level moisture in from the south, which will likely scrape the eastern half of the Big Island over the next 24 hours. This moisture could contribute to periods of fog and high humidity at the summit for tonight and perhaps isolated convection along the Big Island slopes this afternoon. There is a slight chance that the inversion will strengthen a bit as a dry sector moves through the area around late tomorrow morning. However, the aforementioned low will begin to send a cold front through the state later that afternoon. The front is not set to arrive at the Big Island until Saturday afternoon, but more mid-level moisture drawn in from the south combined with building instability will likely erode the inversion and increase the risk for fog/high humidity and light flurries at the summit for Friday night. This risk, as well as the possibility for banding convection and brief periods of moderate snow, will increase as the front passes through the Big Island Saturday night. Fortunately, the front is expected to quickly shift off toward the east, allowing very dry/stable air to move into the area by early Sunday afternoon. A ridge following the departing trough and its front will instill strong/steady large-scale subsidence, which will help rebuild the inversion and ensure dry/stable summit conditions for Sunday and Monday night. Precipitable water will respond to this and plummet toward 0.7-0.8 mm, but passing low-level turbulence in the wake of the front may still contribute to poor seeing for Sunday night; seeing should settle toward 0.5-0.6 arcseconds as this turbulence passes for 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 08 Nov
08 pm HST
Thu 08 Nov
02 am HST
Fri 09 Nov
02 pm HST
Fri 09 Nov
08 pm HST
Fri 09 Nov
02 am HST
Sat 10 Nov
02 pm HST
Sat 10 Nov
08 pm HST
Sat 10 Nov
02 am HST
Sun 11 Nov
02 pm HST
Sun 11 Nov
02 am HST
Mon 12 Nov
02 pm HST
Mon 12 Nov
02 am HST
Tue 13 Nov
00 UTC
Fri 09 Nov
06 UTC
Fri 09 Nov
12 UTC
Fri 09 Nov
00 UTC
Sat 10 Nov
06 UTC
Sat 10 Nov
12 UTC
Sat 10 Nov
00 UTC
Sun 11 Nov
06 UTC
Sun 11 Nov
12 UTC
Sun 11 Nov
00 UTC
Mon 12 Nov
12 UTC
Mon 12 Nov
00 UTC
Tue 13 Nov
12 UTC
Tue 13 Nov
Cloud Cover (%) 60 to 80 20 to 40 20 to 40 70 to 90 60 to 80 70 to 90 80 to 100 80 to 100 80 to 100 20 to 40 0 to 20 0 to 20 0 to 5
Cloud Height (km) above sea level 4-8 4.5-5.5 4.5-6 4-8 4.5-9 4.5-9 4-10 4-10 4-10 9-10 9.5-10 N/A N/A
Chance for Fog/Precip (%) 65/20 60/10 55/10 65/20 75/30 75/30 90/60 95/75 95/60 20/0 0/0 0/0 0/0
PW (mm, summit upward) 4 to 8 3.5 to 4.5 4 to 6 6 to 10 6 to 10 6 to 10 6 to 10 8 to 12 8 to 12 1 to 2 0.6 to 1 0.6 to 1 0.7 to 1.1
Mean Seeing (arcsecs) N/A 0.8 ± 0.15 0.8 ± 0.15 N/A 0.9 ± 0.2 1.0 ± 0.3 N/A 1.2 ± 0.3 1.3 ± 0.4 N/A 0.8 ± 0.2 N/A 0.55 ± 0.1
Summit Temp (°C) 6 2 1 5 0.5 -0.5 3 -1 -1.5 4 -0.5 6 2
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)

SSW/10 to 20

SSW/15 to 30

SSW/15 to 30

WSW/10 to 20

WSW/10 to 20

WSW/15 to 30

WSW/15 to 30

WSW/15 to 30

W/15 to 35

WNW/15 to 30

NNE/15 to 30

NNE/10 to 20

NE/5 to 15


 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.Nov.08/Fri.Nov.09
17:54
19:00
5:12
6:18
N/A
19:09
3
16 26.5
-17 49
Fri.Nov.09/Sat.Nov.10
17:53
19:00
5:12
6:19
N/A
19:56
8
17 18.5
-20 01
Sat.Nov.10/Sun.Nov.11
17:53
18:59
5:13
6:19
N/A
20:44
14
18 10.6
-21 15
Sun.Nov.11/Mon.Nov.12
17:53
18:59
5:13
6:20
N/A
21:33
21
19 02.4
-21 29
Mon.Nov.12/Tue.Nov.13
17:52
18:59
5:13
6:20
N/A
22:24
29
19 53.3
-20 44


Forecast issued by: Ryan Lyman
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Next update at 5 PM HST Thursday 08 November (0300 UTC Friday 9 November) 2018.
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