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Please select a year and month and links of all available forecasts for that period will be given in the 'Select Forecast' menu.
Selection: 2013
02
Feb 15 2013 (afternoon)



Mauna Kea Forecast

Latest Forecast for Mauna Kea Observatories
5 PM HST Friday 15 February (0300 UTC Saturday 16 February) 2013

Warnings
Chance for fog/ice and flurries

Cloud Cover and Precipitation Forecast
There is a high risk for periods of fog, high humidity and ice through the night; precipitation and clouds are unlikely.

Summary of Key Meteorological Variables
Summit temperatures will be near -3.5 C this evening and -4 C tomorrow morning. Winds will be from the NE at 10-20 mph, with seeing around 0.8-1 arcsecond. Precipitable water is expected to be in the 2-3 mm range for the night.

Graphical Summary

Discussion
The tradewind inversion will remain weak/elevated near 13 thousand feet, which will significantly increase the risk for fog, high humidity and ice at the summit for tonight; precipitation is unlikely. The inversion is slated to recover near 10 thousand feet, allowing more normal dry/stable conditions to return to the summit for the following 4 nights. Extensive afternoon clouds are possible for tomorrow, but will become minimal and short-lived for the remainder of the forecast period.

There is a possibility for summit-level clouds as well as convection to the east of the Big Island for tonight. While these clouds are slated to diminish for subsequent nights, high clouds are expected to fill in from the northwest through tomorrow and probably pass overhead for that night as well as most of Sunday night. These clouds will push off toward the SE on Monday, leaving clear skies the remainder of the forecast period.

Precipitable water is expected to increase toward 2-3 mm for tonight, then slip to 0.8-1 mm for the following 3 nights, only to increase to 1-2 mm for Tuesday night.

Minor boundary layer turbulence and/or free atmospheric turbulence will likely contribute to poorer than average seeing probably throughout most of the forecast period. There is a possibilty for periods of bad seeing mostly for tonight.

Not much change since the morning forecast...A patch of rather unstable low-level clouds filling in from the east will continue to interact with a building trough aloft and weaken/lift the inversion toward 13 thousand feet over the next 12-18 hours. This could result in periods of fog, high humidity and iceat the summit for tonight; precipitation is unlikely. Although the trough is expected to linger in the area into the early part of next week, the moisture will quickly shove off toward the west, allowing the mid/low-level ridge (that will remain quasi-stationary/steady to the north of the state) to regain control of the low-level air mass and rebuild the inversion near 10 thousand feet by late tomorrow afternoon, if not sooner. This will ensure the summit-level air mass remains dry and stable for the remainder of the forecast period. The lingering trough aloft will still allow pockets of turbulence to pass overhead, which will probably contribute to poor seeing probably through the next 4-5 nights. There is also a possibility that summit-level winds will steer toward the upper end of the 10-20 mph range, which could stir up boundary layer turbulence particularly over the next 3 nights.

Astronomical Observing Quality Guidance
05 pm HST Friday 15 February (03 UTC Saturday 16 February)CN2
08 pm HST Friday 15 February (06 UTC Saturday 16 February)CN2
11 pm HST Friday 15 February (09 UTC Saturday 16 February)CN2
02 am HST Saturday 16 February (12 UTC Saturday 16 February)CN2
05 am HST Saturday 16 February (15 UTC Saturday 16 February)CN2
08 am HST Saturday 16 February (18 UTC Saturday 16 February)CN2
Latest WRF CN2 Profiles Animation | Collage


5-day Forecast
Summary

Graphical Trend
08 pm HST
Fri 15 Feb
02 am HST
Sat 16 Feb
02 pm HST
Sat 16 Feb
08 pm HST
Sat 16 Feb
02 am HST
Sun 17 Feb
02 pm HST
Sun 17 Feb
08 pm HST
Sun 17 Feb
02 am HST
Mon 18 Feb
02 pm HST
Mon 18 Feb
02 am HST
Tue 19 Feb
02 pm HST
Tue 19 Feb
02 am HST
Wed 20 Feb
02 pm HST
Wed 20 Feb
06 UTC
Sat 16 Feb
12 UTC
Sat 16 Feb
00 UTC
Sun 17 Feb
06 UTC
Sun 17 Feb
12 UTC
Sun 17 Feb
00 UTC
Mon 18 Feb
06 UTC
Mon 18 Feb
12 UTC
Mon 18 Feb
00 UTC
Tue 19 Feb
12 UTC
Tue 19 Feb
00 UTC
Wed 20 Feb
12 UTC
Wed 20 Feb
00 UTC
Thu 21 Feb
Cloud Cover (%) 10 to 30 10 to 30 40 to 60 40 to 60 60 to 80 60 to 80 60 to 80 40 to 60 20 to 40 0 to 20 0 to 20 0 to 20 0 to 20
Cloud Height (km) above sea level N/A N/A 4-4.5 9-10 8-10 8-10 9-10 9-10 9-9.5 N/A N/A N/A N/A
Chance for Fog/Precip (%) 75/25 75/25 25/5 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0 0/0
PW (mm, summit upward) 2 to 3 2 to 3 1 to 2 0.8 to 1 0.8 to 1 0.8 to 1 0.8 to 1 0.8 to 1 0.8 to 1 0.7 to 0.9 1 to 2 1 to 2 2 to 4
Mean Seeing (arcsecs) 0.9 ± 0.2 0.9 ± 0.2 N/A 0.75 ± 0.15 0.75 ± 0.15 N/A 0.75 ± 0.15 0.7 ± 0.1 N/A 0.8 ± 0.2 N/A 0.8 ± 0.2 N/A
Summit Temp (°C) -3.5 -4 1 -3.5 -4 1 -3.5 -4 1 -4 1 -4 1
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)

NE/10 to 20

NE/10 to 20

ENE/10 to 20

ENE/10 to 20

E/10 to 20

E/10 to 20

E/10 to 20

E/10 to 20

E/5 to 15

ESE/0 to 10

E/0 to 10

E/0 to 10

NNE/0 to 10


 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
Fri.Feb.15/Sat.Feb.16
18:31
19:36
5:36
6:41
N/A
23:46
36
2 34.4
15 51
Sat.Feb.16/Sun.Feb.17
18:31
19:36
5:35
6:40
N/A
0:37
45
3 23.8
18 13
Sun.Feb.17/Mon.Feb.18
18:32
19:36
5:35
6:40
N/A
1:27
55
4 13.9
19 45
Mon.Feb.18/Tue.Feb.19
18:32
19:37
5:34
6:39
N/A
2:16
64
5 04.4
20 24
Tue.Feb.19/Wed.Feb.20
18:32
19:37
5:34
6:39
N/A
3:04
73
5 55.4
20 08


Forecast issued by: Ryan Lyman
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Next update at 10 AM HST (2000 UTC) Monday 18 February 2013.
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This page was last modified on: Tue, Jun 23 2015 - 2320 UTC
Send comments to: Ryan Lyman