Current Conditions
Temp2.2 C
RH96 %
WindNW 35 mph
RoadOpen (4x4 only)
Mauna Kea Observatories Forecast
5 PM HST Monday 31 August (0300 UTC Tuesday 1 September) 2015
High humidity and fog
Chance rain and convection
Cloud Cover and Fog/Precipitation Forecast
There is a high risk for fog as humidity continues to linger near or exceed 80% through the night. Light precipitation, mid/summit-level clouds and perhaps isolated convection are also possible mainly for this afternoon/evening and again around sunrise tomorrow.
Summary of Key Meteorological Variables
Summit temperatures will be near 3 C, with winds from the NW at 10-20 mph for this evening, switching to a more westerly direction through the night. Seeing and precipitable water are expected to linger near or exceed 1 arcsecond and 4 mm, respectively, through the night.
The atmosphere near the Big Island (particularly the mid-level portion) will remain fairly saturated and unstable, which will allow humidity to linger near or exceed 80% likely through the next 5 nights. Consequently, there is a high risk for fog at the summit during this time. There is also a possibility for possibility for periods of rain and convection in the area especially during the afternoon hours and near sunrise. Extensive daytime clouds are expected throughout the forecast period.

Although the summit will steer free of organized widespread clouds throughout the forecast period, there is a possibility for small patches of summit/mid-level clouds in the area during this time. Thick clouds will also litter the north and eastern skies, and may occasionally drift over/near the Big Island mainly through Thursday night.

Precipitable water is expected to exceed 8 mm through the next 5 nights.

Pockets of turbulence are expected to move over the summit area, likely contributing to poor/bad seeing through at least Wednesday night. Although mediocre/poor conditions will likely continue to prevail thereafter, there is a possibility for relatively calm flow aloft, which may allow for better than average seeing for Thursday and especially Friday night.

No change since the morning forecast....Although Ignacio is scheduled to pass 200-300 km to the northeast of the state over the next several days, widespread moisture and instability surrounding the storm is still expected to linger over/near the Big Island area during this time and may persist into the weekend. This will keep the atmosphere near the Big Island mostly saturated and allow summit-level humidity to linger near or exceed 80% over the next 5 nights. Consequently, there is a very high risk for extensive fog at the summit as well as periods of rain and convection in the area, especially, but not limited to, the afternoon hours and near sunrise. The bulk of the clouds associated with Ignacio are slated to pass to the northeast of the Big Island, but there is a possibility that stray patches of mid/summit-level clouds will drift over/near the summit particularly through the next 2 nights. There is also a chance that high clouds will drift in from the southwest later in the week. Pockets of turbulence associated with Ignacio is also expected pass over the summit area, contributing to poor/bad seeing over the next 3 nights. There is a very good chance that these pockets will shift further northward with the storm, which should allow seeing to improve dramatically for Thursday and especially Friday night. As for Jimena, its still too early to antcipate its track, intensity and impact to the state/summit, but the last several model runs suggests that it will come to a crawl upon reaching 145W, track north for 500 km or so, then hopefully pass 600-800 km to the northeast of the state over the weekend (it should maintain its intensity through this time). If this holds true, it should have little to no impact on summit, at least through the Labor Day weekend.
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)
Mon Aug 31 - 8 PM40-604-690 / 603NW/10-200.7-1.18-12
Tue Sep 01 - 2 AM30-504-690 / 653W/10-200.8-1.28-12
2 PM80-1004-10100 / 906SW/5-15NaN12-16
8 PM60-804-895 / 752.5S/5-150.9-1.512-16
Wed Sep 02 - 2 AM60-804-690 / 752SSW/5-150.8-1.412-16
2 PM80-1004-895 / 906SSW/10-20NaN12-16
8 PM60-804-690 / 602.5S/5-150.8-1.212-16
Thu Sep 03 - 2 AM40-604-690 / 502.5SSW/5-150.7-1.112-16
2 PM60-804-895 / 756S/5-15NaN12-16
Fri Sep 04 - 2 AM20-408-980 / 402.5SSE/5-150.45-0.6512-16
2 PM60-804-690 / 757.5W/5-15NaN12-16
Sat Sep 05 - 2 AM0-209-1075 / 253WNW/0-100.35-0.5510-15
2 PM60-804-1090 / 607.5NNW/5-15NaN10-15
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
Mon Aug 31 - Tue Sep 01 18:47 19:53 4:52 5:57 20:19 N/A 90 1 03.1 4 43
Tue Sep 01 - Wed Sep 02 18:46 19:52 4:52 5:58 21:07 N/A 81 2 00.7 9 00
Wed Sep 02 - Thu Sep 03 18:45 19:51 4:52 5:58 21:56 N/A 71 2 57.9 12 35
Thu Sep 03 - Fri Sep 04 18:44 19:50 4:53 5:58 22:46 N/A 60 3 54.8 15 17
Fri Sep 04 - Sat Sep 05 18:43 19:49 4:53 5:58 23:37 N/A 49 4 51.0 17 01
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 1 September 2015.
Additional Information
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