Current Conditions
Temp5.1 C
RH42 %
WindNNW 9 mph
Mauna Kea Observatories Forecast
4 PM HST Tuesday 16 July (0200 UTC Wednesday 17 July) 2019
Cloud Cover and Fog/Precipitation Forecast
The summit will be mostly dry and stable through tonight.
Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C this evening and 2.5 C tonight. Winds will be from the SE at 5-15 mph through the night. PW will range between 2.5 and 3 mm. Observing conditions will be average to better than average.
Overall the tradewind inversion will remain in place and continue to promote mostly stable conditions at the summit throughout the forecast period. Nevetheless, latest sounding shows a slighly weaker inversion, due to the closeness of the upper level disturbance. This has allowed for daytime clouds today to reach the summit and somewhat higher RH. Daytime clouds will dissipate through this afternoon/evening, and mostly dry and stable conditions will characterize tonigh. Moisture though, will continue in fact to average 30 to 50%, at least through Thursday and early Friday, likely resulting in daytime clouds through them. Small chances are for lingering fog in the evening hours for Wednesday and Thursday. A drying trend should follow for the Friday and Saturday night.

Summit skies will be predominantly clear tonight. Banding high clouds will instead approach the summit later tomorrow and will cross the area moving from the SE to the NW through the night, likely obscuring at least 50% of the summit sky. More clear skies will follow but for lingering daytime clouds which might be on the way of observations particularly on Thursday night.

Precipitable water will range between 2.5 and 3 mm tonight, it is likely to exceed the 4 mm threshould on Wednesday and Thursday night, to then start decreasing and range between 3 and 4 mm on Friday night and linger close to 1.5 mm on Saturday night.

Observing conditions will be average to better than average tonight, while are projected to degrade for the following two nights as surface winds pick up and boundary layer turbulence, along with moisture in the airmasses, will make it for less than average to poor seeing. An improving trend is expected for Friday and Sunday night as winds taper and the airmasses slowly dry out.

No changes since the morning forecast... The persisting high pressure system North of the State will continue to promote astable tradewind inversion which will help capping most of the low level moisture below the summit level throughout most of this forecast period. Nevertheless a weak upper level low approaching from the East will advect over the State some moisture, somewhat destabilizing the air masses from today through Thursday. While the effect will not be very large, relative humidity is likely to remain high through then, resulting in extensive daytime clouds and possibly lingering moisture during the evening hours, particularly on Wednesday and Thursday. Meanwhile also tighter pressure gradients are likely to increase surface wind speed on Wednesday and Thursday. Drying conditions will return on Friday and through the weekend when also surface winds will taper...
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)
Tue Jul 16 - 8 PM0-20Clear0 / 03.5SW/0-100.4-0.73-4
Wed Jul 17 - 2 AM0-20Clear0 / 02.5SE/5-150.45-0.752.5-3
2 PM10-303.5-4.540 / 07.5S/15-25NaN3-5
8 PM0-20Clear60 / 03SE/15-250.7-1.14-6
Thu Jul 18 - 2 AM20-407-860 / 02E/15-250.8-1.24-8
2 PM60-806-850 / 07ESE/20-30NaN4-8
8 PM20-403-4.530 / 03E/20-300.6-14-6
Fri Jul 19 - 2 AM20-403-510 / 02.5E/20-300.6-13-5
2 PM20-403.5-4.530 / 07ESE/15-25NaN3-5
Sat Jul 20 - 2 AM0-20Clear0 / 02N/10-200.4-0.83-4
2 PM0-20Clear0 / 08NE/5-15NaN1.5-2.5
Sun Jul 21 - 2 AM0-20Clear0 / 03ESE/5-150.35-0.751.25-1.75
2 PM0-20Clear0 / 010SE/5-15NaN1-2
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
Tue Jul 16 - Wed Jul 17 19:14 20:26 4:30 5:42 19:07 N/A 100 20 12.1 -21 48
Wed Jul 17 - Thu Jul 18 19:13 20:26 4:31 5:43 19:53 N/A 98 21 03.8 -19 45
Thu Jul 18 - Fri Jul 19 19:13 20:25 4:31 5:43 20:35 N/A 94 21 53.3 -16 52
Fri Jul 19 - Sat Jul 20 19:13 20:25 4:32 5:44 21:14 N/A 89 22 40.7 -13 19
Sat Jul 20 - Sun Jul 21 19:13 20:25 4:32 5:44 21:51 N/A 82 23 26.5 -9 18
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Wednesday 17 July 2019.
Additional Information
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