Latest Forecast for Mauna Kea Observatories
5 PM HST Monday 29 June (0300 UTC Tuesday 30 June) 2020

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 2.5 C this evening and 3 C tomorrow morning. Winds will be from the SSE at 5-15 mph, with seeing near 0.35-0.4 arcseconds. Precipitable water is expected to be in the 0.8-1 mm range for the night.

Graphical Summary

Discussion
A very well-defined tradewind inversion will continue to cap low-level moisture near 6-7 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.

Skies overhead will remain predominately clear through the next 5 nights.

Precipitable water is expected to linger below 1 mm for tonight, jump to 2-3 mm for the next 2 nights, then slip back to 1-1.5 mm for Thursday and Friday night.

A stable air mass, combined with calm skies and laminar south to SW flow in the free atmosphere should allow for excellent seeing for at least the next 2 nights. There is a chance for minor low-level turbulence, which could subtly degrade seeing (toward 0.4-0.5) arcseconds for Wednesday, Thursday and Friday night.

No change since the morning forecast...The mid/low-level ridge will continue to sit to the NE and promote steady/strong large-scale subsidence in the area through the week. This subsidence will easily maintain a well-defined inversion near 6-7 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. A stable air mass, combined with a somewhat northward displacement of the tropical upper-tropospheric trough will allow calm skies to prevail above the summit through this time. While this will likely help keep seeing at or below 0.4 arcseconds over the next 2 nights, there is a chance that the mid-level wind gradient will tighten as a tropical wave passes to the south beginning Wednesday morning. This could result in a slight increase in summit-level winds and perhaps a minor degradation in seeing for the remainder of the forecast period.

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
08 pm HST
Mon 29 Jun
02 am HST
Tue 30 Jun
02 pm HST
Tue 30 Jun
08 pm HST
Tue 30 Jun
02 am HST
Wed 01 Jul
02 pm HST
Wed 01 Jul
08 pm HST
Wed 01 Jul
02 am HST
Thu 02 Jul
02 pm HST
Thu 02 Jul
02 am HST
Fri 03 Jul
02 pm HST
Fri 03 Jul
02 am HST
Sat 04 Jul
02 pm HST
Sat 04 Jul
06 UTC
Tue 30 Jun
12 UTC
Tue 30 Jun
00 UTC
Wed 01 Jul
06 UTC
Wed 01 Jul
12 UTC
Wed 01 Jul
00 UTC
Thu 02 Jul
06 UTC
Thu 02 Jul
12 UTC
Thu 02 Jul
00 UTC
Fri 03 Jul
12 UTC
Fri 03 Jul
00 UTC
Sat 04 Jul
12 UTC
Sat 04 Jul
00 UTC
Sun 05 Jul
Cloud Cover (%) 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 0 to 20
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) 0.8 to 1 0.8 to 1 1 to 2 2 to 3 2 to 3 2 to 3 2 to 3 2 to 3 1 to 2 1 to 1.5 1 to 2 1 to 1.5 1 to 2
Mean Seeing (arcsecs) 0.35 ± 0.1 0.4 ± 0.1 N/A 0.35 ± 0.1 0.4 ± 0.1 N/A 0.45 ± 0.1 0.45 ± 0.1 N/A 0.45 ± 0.1 N/A 0.45 ± 0.1 N/A
Summit Temp (°C) 2.5 3 9.5 5 4.5 11 6 5.5 10.5 4.5 9 4 8
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)

SSE/5 to 15

SSE/5 to 15

SSE/5 to 15

SSE/5 to 15

SE/0 to 10

ENE/5 to 15

ENE/10 to 20

ENE/10 to 20

ENE/10 to 20

ENE/10 to 20

NE/10 to 20

ENE/10 to 20

ENE/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
Mon.Jun.29/Tue.Jun.30
19:15
20:29
4:23
5:37
N/A
2:07
73
14 19.7
-10 12
Tue.Jun.30/Wed.Jul.01
19:15
20:29
4:23
5:37
N/A
2:52
82
15 14.8
-15 20
Wed.Jul.01/Thu.Jul.02
19:15
20:29
4:24
5:37
N/A
3:40
90
16 12.2
-19 36
Thu.Jul.02/Fri.Jul.03
19:15
20:29
4:24
5:38
N/A
4:33
96
17 11.8
-22 43
Fri.Jul.03/Sat.Jul.04
19:15
20:29
4:24
5:38
17:56
5:29
99
18 12.8
-24 26


Forecast issued by: Ryan Lyman
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Next update at 10 AM HST (2000 UTC) Tuesday 30 June 2020.
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