Latest Forecast for Mauna Kea Observatories
10 AM HST (2000 UTC) Monday 30 March 2020

Warnings
None

Cloud Cover and Precipitation Forecast
There is a strong possibility for periods of fog and ice as humidity lingers in the 60-80% range through the night; precipitation is unlikely, while scattered to broken high clouds fill in from the west through the night.

Summary of Key Meteorological Variables
Summit temperatures will be near 0 C this afternoon, -3 C this evening and -3.5 C tomorrow morning. Winds will be from the WNW at 15-30 mph for today and 10-20 mph for the night. Seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm, respectively, through the night.

Graphical Summary

Discussion
Although there is a chance that the air mass will begin to dry out this afternoon/evening, the inversion will remain rather weak/indistinct as humidity lingers near 60-80% for tonight. In addition, more widespread moisture is set to build into the area around sunrise tomorrow and persist probably into Thursday evening. There is a chance that another large patch will drift in from the south over the weekend. Consequently, there is a moderate/high risk for extensive fog, ice and flurries at the summit throughout the forecast period. There is also a chance for periods of moderate/heavy snow and convection in the area, mainly between tomorrow afternoon and Thursday morning. Extensive daytime clouds are expected throughout the forecast period.

Scattered to broken mid/upper-level clouds will continue to fill in from the west contributing to extensive cloud cover for tonight. Thicker more widespread clouds will fill in to the area just after sunrise tomorrow, with additional high clouds drifting in from the west later in the week. Nevertheless, this will likely result in overcast skies for the remainder of the forecast period.

Precipitable water is expected to exceed 4 mm throughout the forecast period.

A fairly saturated/unstable air mass, combined with instability and even periods of upper-level turbulence will contribute to bad seeing through the next 5 nights.

The mid-level ridge will remain rather indistinct as the tropical upper-tropospheric trough persists to the west of the state before being replaced by a rather large low developing to the NW of the state later in the week. Nevertheless, the presence of the TUTT (and the absence of the ridge) will allow widespread weak instability to prevail in the area over the next several days, and will eventually be re-inforced by the low over the weekend. There is a chance that the mid-level air mass will begin to dry out as a low embedded in the TUTT continues to depart eastward this afternoon/evening. However, a new embedded short-wave trough filling in from the west will help kink the sub-tropical jet and send lots of high clouds overhead for tonight. This trough will eventually enhance the instability in the area, which will probably help saturate the bulk of the air mass between sunrise tomorrow and early Thursday evening. There is a chance that the air mass will dry up a bit as this trough shifts eastward through Thursday night, but the introduction of the large low to the NW will quickly drag tropical moisture into the area by early Friday morning and probably into the weekend. As a result, there is a very good chance that high humidity, fog, ice and periods of flurries will plague the summit throughout most of the forecast period. There is also a possibility for convection in the area and perhaps periods of moderate/heavy snow mainly between tomorrow afternoon and Thursday morning.

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 30 Mar
08 pm HST
Mon 30 Mar
02 am HST
Tue 31 Mar
02 pm HST
Tue 31 Mar
08 pm HST
Tue 31 Mar
02 am HST
Wed 01 Apr
02 pm HST
Wed 01 Apr
08 pm HST
Wed 01 Apr
02 am HST
Thu 02 Apr
02 pm HST
Thu 02 Apr
02 am HST
Fri 03 Apr
02 pm HST
Fri 03 Apr
02 am HST
Sat 04 Apr
00 UTC
Tue 31 Mar
06 UTC
Tue 31 Mar
12 UTC
Tue 31 Mar
00 UTC
Wed 01 Apr
06 UTC
Wed 01 Apr
12 UTC
Wed 01 Apr
00 UTC
Thu 02 Apr
06 UTC
Thu 02 Apr
12 UTC
Thu 02 Apr
00 UTC
Fri 03 Apr
12 UTC
Fri 03 Apr
00 UTC
Sat 04 Apr
12 UTC
Sat 04 Apr
Cloud Cover (%) 60 to 80 60 to 80 60 to 80 80 to 100 80 to 100 80 to 100 80 to 100 80 to 100 80 to 100 80 to 100 80 to 100 80 to 100 80 to 100
Cloud Height (km) above sea level 4-10 6-10 5-10 4-10 4-9 4-8 4-10 4-8 4-8 4-9 5-10 4-10 4-10
Chance for Fog/Precip (%) 90/40 65/15 75/25 95/90 100/95 100/95 100/95 95/90 95/90 95/75 75/40 90/60 90/65
PW (mm, summit upward) 6 to 10 6 to 10 6 to 10 8 to 12 8 to 12 8 to 12 8 to 12 8 to 12 6 to 10 6 to 10 4 to 8 6 to 10 6 to 10
Mean Seeing (arcsecs) N/A 1.0 ± 0.3 1.0 ± 0.3 N/A 1.5 ± 0.5 1.5 ± 0.5 N/A 1.5 ± 0.5 1.2 ± 0.4 N/A 1.2 ± 0.4 N/A 1.2 ± 0.4
Summit Temp (°C) 0 -3 -3.5 -1 -3 -4 -1 -4 -4 -1 -3 0 -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)

WNW/15 to 30

WNW/10 to 20

WNW/10 to 20

W/5 to 15

WNW/5 to 15

WSW/5 to 15

SSW/0 to 10

WSW/5 to 15

WSW/5 to 15

WSW/10 to 20

SW/10 to 20

SSW/10 to 20

SW/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
Mon.Mar.30/Tue.Mar.31
18:45
19:50
5:02
6:07
N/A
0:27
39
5 52.3
22 47
Tue.Mar.31/Wed.Apr.01
18:45
19:50
5:01
6:06
N/A
1:22
49
6 48.5
23 28
Wed.Apr.01/Thu.Apr.02
18:45
19:50
5:00
6:05
N/A
2:17
60
7 46.6
22 49
Thu.Apr.02/Fri.Apr.03
18:46
19:51
4:59
6:04
N/A
3:09
70
8 45.7
20 46
Fri.Apr.03/Sat.Apr.04
18:46
19:51
4:58
6:03
N/A
3:59
80
9 44.7
17 21


Forecast issued by: Ryan Lyman
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Next update at 5 PM HST Monday 30 March (0300 UTC Tuesday 31 March) 2020.
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