Current Conditions
Temp9.2 C
RH15 %
WindNNW 11 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Friday 06 May 2016
Chance for fog/high humidity
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for periods of fog and high humidity throughout the night; precipitation is not expected and skies will remain predominately clear.
Summary of Key Meteorological Variables
Summit temperatures will be near 7 C this afternoon and 2 C for the night. Winds will be from the west at 5-15 mph for today, increasing to 15-30 mph through the night. Seeing will likely be near 0.7-0.75 arceseconds, while precipitable water is expected to be in the 2-3 mm range for the first half of the night and 1.5-2 mm range for the second half.
The tradewind inversion is slated to weaken and lift toward 11-12 thousand feet for the next 2 nights, further deteriorate to 13-13.5 thousand feet for Sunday and Monday night, then recover a bit for Tuesday night. Nonetheless, there is a risk for periods of fog and high humidity throughout the next 5 nights. There is also a chance for light precipitation at the summit mainly for Sunday and Monday night. Daytime clouds are expected to pick up today, and could turn extensive for the remainder of the forecast period; there is an outside risk for isolated afternoon convection along the slopes mainly for for Sunday and Monday.

Skies will remain predominately clear for tonight and perhaps tomorrow evening, but high clouds are slated to fill in from the west and pass mainly along the northern skies during the latter night and for Sunday night. While the bulk of the high clouds are set to shift eastward thereafter, there is a chance for summit-level clouds for Sunday and Monday night; skies should open up again for Tuesday night.

Precipitable water is expected to increase toward 3 mm for this evening, but could slip toward 1.5 mm as the night progresses and perhaps toward 1 mm for tomorrow night. However, it will likely increase back to 3+ mm for Sunday and Monday night, then trend back to 1 mm through Tuesday night.

With the brief exception of later tonight, calm skies should prevail at the surface level throughout the forecast period. However, there is a good chance for building upper-level turbulence/instability over the next 2 nights, that will eventually give way to stronger upper-level turbulence for Sunday night and early part of next week. Consequently, poorer than average seeing will likely plague the summit through the next 5 nights, with a chance for bad seeing mainly for Sunday and Monday night.

The mid/low-level ridge will continue to shift off toward the east as trough/low passes to the north and sends a cold front toward the state over the next 24 hours. Although the bulk of the instability associated with the trough is set to pass to the north, while the front will probably not reach the Big Island, moisture filling in from the SE is expected to accumulate in the area over the next 12 hours, likely lifting the inversion toward 10-12 thousand feet by later tonight and for tomorrow night. This may allow for periods of fog and high humidity at the summit over the next 2 nights, though the odds are still quite low because of the absence of any prominent low-level forcing to overcome what's left of the inversion. However, a new low-level ridge gradually filling in behind the departing trough may push what's left of the front over the Big Island area and further weaken/lift the inversion toward 13-13.5 thousand feet between late Sunday afternoon and sunrise on Tuesday. In addition, a strong sub-tropical jet is set to build in over the southern half of the state in the wake of the departing trough, perhaps bringing pockets of upper-level instability/vorticity (and turbulence) to the area for the second half of the weekend and early part of next week. Consequently, it wouldn't take much low-level forcing to allow for development of fog or even summit-level clouds (and thus light precipitation) mainly for Sunday and Monday night. The bulk of the moisture will eventually detrain into the surrounding atmosphere and/or shift off toward the SW with the building low-level trades around Tuesday. This should help reduce the risk for fog/high humidity at the summit for the remainder of the week.
WRF Astronomical Observing Quality Guidance
Cloud Cover and Precipitable Water Analyses
MK CN² Profiles
5 Day Forecast Summary (Graphical Trend)
HST Cloud Fog/Precip Temp Wind Seeing PW
Cover (%) Height (km) Probability (%) (Celcius) (Dir/MPH) (Arcseconds) (mm)
Fri May 06 - 2 PM20-404-4.540 / 107WSW/5-15NaN2-4
8 PM0-5Clear25 / 52W/10-200.5-0.92-3
Sat May 07 - 2 AM0-5Clear25 / 52WNW/15-300.5-11.5-2
2 PM20-404-550 / 107W/10-20NaN3-6
8 PM0-20Clear25 / 52.5NW/5-150.5-0.91-1.5
Sun May 08 - 2 AM20-409-1030 / 52N/5-150.5-0.90.8-1.2
2 PM60-804-1075 / 257SSW/0-10NaN3-6
8 PM60-804-1060 / 202NW/0-100.6-1.23-5
Mon May 09 - 2 AM60-804-1060 / 201WNW/0-100.7-1.33-5
2 PM80-1004-1080 / 405NNW/5-15NaN4-8
Tue May 10 - 2 AM20-404-550 / 101NW/10-200.6-1.22-4
2 PM40-604-540 / 07NW/5-15NaN2-4
Wed May 11 - 2 AM0-5Clear25 / 52NW/5-150.5-11-2
Rise and Set times for the Sun and Moon
Night (HST) Sun Set Twilight End Twilight Beg Sun Rise Moon Rise Moon Set Illumination (%) RA DEC
Fri May 06 - Sat May 07 18:57 20:06 4:30 5:40 6:43 19:16 1 3 37.7 14 09
Sat May 07 - Sun May 08 18:57 20:07 4:30 5:39 N/A 20:20 4 4 38.3 16 32
Sun May 08 - Mon May 09 18:58 20:07 4:29 5:39 N/A 21:22 10 5 38.7 17 47
Mon May 09 - Tue May 10 18:58 20:08 4:28 5:38 N/A 22:21 17 6 38.0 17 50
Tue May 10 - Wed May 11 18:58 20:08 4:28 5:38 N/A 23:15 26 7 35.1 16 49
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Friday 06 May (0300 UTC Saturday 7 May) 2016.
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