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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: 2003
 11
 Nov 19 2003 (morning)


Mauna Kea Forecast Latest Forecast for Mauna Kea Observatories
10 AM HST (2000 UTC) Wednesday 19 November 2003

Warnings
None

Cloud Cover and Precipitation Forecast
There is a slim chance for fog during the first 2-3 hours of the night; dry air is expected after that. Precipitation is not expected through the night. Cloud cover is expected to decrease to < 10% as the high clouds to the north of the summit dissipate over the next 12 to 24 hours.

Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C today and -1 C tonight. Precipitable water is expected to be near 2.5 to 3.5 mm tonight and 1 to 1.5 mm tomorrow morning. Winds will be from the NNW at 15 to 25 mph for today and 25 to 35 mph for the night. Shear is expected to be near 35 to 45 mph for tonight and 45 to 55 mph during the morning hours.

Discussion
The inversion is slated to briefly weaken as a band of low-level moisture moves through the area over the next 6 hours. Thus, there is a good chance for fog, extensive clouds, and light precipitation today, some of the fog/clouds may linger into the first few hours of the night. The inversion is expected to quickly strengthen this evening, and it should be at full strength at 6-7 thousand feet by midnight. It will likely remain very strong through Friday night. As a result, fog or precipitation is not expected during this time. Another weak band of low-level moisture is slated to move in from the northeast on Saturday and Sunday night. Although it will hardly affect the strenght of the inversion, it may bring a slight chance for fog on those days/nights. Daytime clouds will be very minimal on Thursday and Friday, but could pick up a bit this weekend.

The scattered high clouds to the north of the summit are expected to dissipate over the next 12 hours, leaving mostly clear skies for tonight. More scattered/isolated cirrus is expected to move in from the northwest later tomorrow and again on Friday night. More organized, but still scattered, cirrus is projected to move in from the north on Saturday and Sunday night. While most of these clouds are not expected to be directly over the summit between Thursday and Sunday night, skies are not expected to be totally clear.

Precipitable water is expected to start out near 3 mm for tonight, then quickly drop towards 1 mm over the second half of the night. It will eventually bottom out near 0.8 mm tomorrow night, then increase toward 1.2 mm on Friday and Saturday night. By Sunday night it could increase toward 1.5-2 mm.

WARNING: Summit winds are slated to increase over the next 24-48 hours. It is expected to peak at 50 mph, with gusts near 60 mph, Friday afternoon/evening, then slowly subside over the next 2-3 days.

It appears that everything is happening according to the previous plan. Currently a band of mid/low-level moisture and diffluence (aka a shearline) has begun to pass through the Big Island. While most of the action associated with this shearline is below 10 thousand feet, the summit will very likely get extensive clouds, fog, and possibly some light rain. Fortunately, the shearline is slated to be south of the summit by this evening, in which case, the summit should dry out for the night. In fact, very dry and stable air is expected in the wake of the shearline. This air mass can be somewhat attributed to the development of a sub-tropical low to the northeast of the state. This low is expected to slowly dig down toward the Islands over the next 4-5 days. In doing so, it will dramatically increase summit level winds to > 50 mph. Fortunately, the summit will be situated on the dry subsiding side of the low. Thus, cloud cover should be very minimal and turbulence in the free atmosphere is expected to be fairly low. And while seeing and precipitable water will also be, for the most part, low (near 0.6 arcsecs and 0.9-1 mm respectively) for the next few days, it will likely undergo more fluctuations as mesoscale pockets of mid/upper eddies and moisture produced by the low move through the area. Eventually the low is slated to move over the Islands as it gains upper-level reinforcement on Sunday and into next week. IF this pans out, look for conditions and viewing to deteriorate as the atmosphere will become fairly moist.

Astronomical Observing Quality Guidance
Seeing/Cn2 Images are not available today. Sorry for the inconvenience.



5-day Forecast
Summary
Trends
02 pm HST
Wed 19 Nov
08 pm HST
Wed 19 Nov
02 am HST
Thu 20 Nov
02 pm HST
Thu 20 Nov
08 pm HST
Thu 20 Nov
02 am HST
Fri 21 Nov
02 pm HST
Fri 21 Nov
02 am HST
Sat 22 Nov
02 pm HST
Sat 22 Nov
02 am HST
Sun 23 Nov
02 pm HST
Sun 23 Nov
02 am HST
Mon 24 Nov
00 UTC
Thu 20 Nov
06 UTC
Thu 20 Nov
12 UTC
Thu 20 Nov
00 UTC
Fri 21 Nov
06 UTC
Fri 21 Nov
12 UTC
Fri 21 Nov
00 UTC
Sat 22 Nov
12 UTC
Sat 22 Nov
00 UTC
Sun 23 Nov
12 UTC
Sun 23 Nov
00 UTC
Mon 24 Nov
12 UTC
Mon 24 Nov
Cloud Cover (%) 50 to 75 5 to 15 0 to 10 0 to 10 5 to 15 0 to 10 0 to 10 0 to 10 0 to 10 5 to 15 5 to 15 10 to 20
Chance for Fog/Precip (%) 50/25 5/0 0/0 0/0 0/0 0/0 0/0 0/0 10/0 10/0 10/0 20/0
PW (mm, summit upward) 4 to 6 2.5 to 3.5 1 to 1.5 0.75 to 1.25 0.75 to 1.25 0.75 to 1.25 1 to 1.5 1 to 1.5 1 to 1.5 1 to 1.5 1.25 to 1.75 1.5 to 2.5
Summit Temp (oC) 3.5 -1 -1 4.5 0 -1 4 -1 4.5 -0.5 5 0
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)

NNW/15 to 25
NW/24
W/33
W/42
W/43
WNW/46
WNW/45
WNW/31
NNW/25 to 35
NW/21
WNW/31
W/44
WNW/48
WNW/50
WNW/54
WNW/34
NNW/25 to 35
NNW/20
NW/29
NW/39
NW/49
NW/62
NW/55
WNW/36
N/25 to 40
NW/24
NW/34
NW/55
NNW/69
NW/72
WNW/62
NW/50
NNW/30 to 45
NW/32
NW/41
NW/57
NW/70
NW/70
WNW/62
NW/45
NW/30 to 45
NW/36
WNW/51
WNW/64
NW/78
NW/82
WNW/58
NW/48
NW/35 to 50
WNW/46
WNW/45
NW/65
NW/83
NW/87
NW/64
WNW/55
NW/35 to 50
WNW/49
NW/57
NW/81
NW/82
NW/88
NW/66
NW/55
NNW/35 to 50
NW/48
NW/54
NW/61
NW/69
NW/72
WNW/61
NW/54
NW/15 to 30
NW/26
NW/30
NW/41
NW/53
NW/62
NW/64
NW/37
W/15 to 30
W/26
WNW/33
WNW/39
NW/40
NW/45
NW/42
WNW/43
W/15 to 30
N/A
N/A
N/A
N/A
N/A
N/A
N/A


 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
Wed.Nov.19/Thu.Nov.20
17:51
18:58
5:17
6:24
3:02
N/A
17
12 39.2
-0 25
Thu.Nov.20/Fri.Nov.21
17:51
18:58
5:17
6:25
4:02
N/A
9
13 30.7
-6 54
Fri.Nov.21/Sat.Nov.22
17:51
18:58
5:18
6:25
5:05
16:17
3
14 24.8
-13 10
Sat.Nov.22/Sun.Nov.23
17:51
18:58
5:18
6:26
6:13
17:03
0
15 22.6
-18 46
Sun.Nov.23/Mon.Nov.24
17:51
18:58
5:19
6:26
7:22
17:54
0
16 24.2
-23 13


Forecast issued by: Ryan Lyman
rlyman@hawaii.edu
(808) 932-2323

Next update at 5 PM HST Wednesday 19 November (0300 UTC Thursday 20 November) 2003.
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This page was last modified on: Wed, Apr 22 2009 - 2058 UTC
Send comments to: Ryan Lyman