Current Conditions
Temp5.4 C
RH20 %
WindNE 13 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
4 PM HST Wednesday 20 June (0200 UTC Thursday 21 June) 2018
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit skies will be predominantly clear today.
Summary of Key Meteorological Variables
Summit temperature will be near 4C this evening and 3.5C tonight and tomorrow morning. Precipitable water will linger close to 3m through the night. Winds will be weak at 5 to 15mph. Observing conditions are on an improving trend and seeing will be in the 0.55-0.65 range.
Discussion
The tradewind inversion will continue to cap the bulk of the low level moisture below summit level through the forecast period. The very latest sounding shows a drier mid level environment therefore relative humidity should finally drop during the nigth hour tonight. The inversion is expected to weaken/lift some later on Friday/Saturday, but it is not expected to vanish completely. So, all in all, expect mostly stable conditions throughout.

Summit skies will be predominantly clear throughout the forecast period. Some high clouds might start being visible along the Eastern horizon late on Sunday.

Precipitable water will linger close to 3 mm tonight, will range between 2.5 and 3 mm on Thursday night and will drop further and be close to 1.5 by Friday night and through Sunday night.

Observing conditions are on an improving trend as airmasses are drying out and winds at the surface taper. Chances are for average seeing conditions tonight and tomorrow, possibly degrading during the second half of the night then. Conditions are expected to be average but with some degree of variability through the rest of the forecast period as winds at the surface will be picking up some and will therefore be stirring up some ground layer turbulence then.

Not much is changed since the morning forecast... As a weak front slowly drifts to the East and the weak high pressure ridge remains to the north of the state, the mid level atmosphere dries out and winds at the surface taper. Therefore weather conditions will be generally good and seeing will finally get into more average values starting tonight. From Thursday a strong surface high pressure will build into the central pacific area and mostly stable conditions will persist through the rest of the forecast period. Nevertheless an upper level low the models project to develop East of the islands, is expected to get closer by Sunday and it might weakly impact conditions at the summit by advecting over some clouds and increasing shear then. It should quickly move out of the way by the beginning of the coming 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)
Wed Jun 20 - 8 PM0-20Clear0 / 04E/5-150.45-0.753-4
Thu Jun 21 - 2 AM0-20Clear0 / 03.5E/5-150.4-0.72.75-3.25
2 PM0-20Clear0 / 09.5ENE/10-20NaN3-4
8 PM0-20Clear0 / 03.5NE/10-200.4-0.82.5-3
Fri Jun 22 - 2 AM0-20Clear0 / 03NE/15-250.6-12.5-3
2 PM0-20Clear0 / 09ENE/15-25NaN1.5-2.5
8 PM0-20Clear0 / 02.5E/15-250.6-11.25-1.75
Sat Jun 23 - 2 AM0-20Clear0 / 02ENE/10-200.45-0.851.5-2
2 PM0-20Clear0 / 09ENE/15-25NaN1-2
Sun Jun 24 - 2 AM0-20Clear0 / 01.5NE/15-250.45-0.851-1.5
2 PM0-20Clear0 / 08ENE/15-25NaN1.5-2.5
Mon Jun 25 - 2 AM10-307-80 / 01ENE/10-200.45-0.851-1.5
2 PM10-307-80 / 09ENE/10-20NaN1-2
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
Wed Jun 20 - Thu Jun 21 19:13 20:27 4:20 5:34 N/A 1:25 60 12 48.1 -0 43
Thu Jun 21 - Fri Jun 22 19:14 20:28 4:20 5:34 N/A 2:05 70 13 37.3 -5 19
Fri Jun 22 - Sat Jun 23 19:14 20:28 4:20 5:34 N/A 2:44 79 14 26.2 -9 37
Sat Jun 23 - Sun Jun 24 19:14 20:28 4:21 5:35 N/A 3:25 87 15 15.4 -13 28
Sun Jun 24 - Mon Jun 25 19:14 20:28 4:21 5:35 N/A 4:07 93 16 05.2 -16 40
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Thursday 21 June 2018.
Additional Information
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This message is also available at the MKWC road conditions page.
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