Current Conditions
Temp2.1 C
RH14 %
WindNE 27 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
4 PM HST Friday 22 June (0200 UTC Saturday 23 June) 2018
Moderate winds
Cloud Cover and Fog/Precipitation Forecast
Summit skies will be predominantly clear tonight.
Summary of Key Meteorological Variables
Summit temperature will be near 2.5C this evening and 1C tonight and tomorrow morning. Precipitable water will linger close to 1.5m through the night. Winds from the E will be moderate at 15 to 25mph, decreasing through the night. Seeing will be less than average to poor and variable.
The tradewind inversion, although more elevated, will cap the bulk of the low level moisture at or below summit level throughout most of this forecast period. The mid/high level airmasses will moisten in time from Sunday and through the end of this forecast period, possibly resulting in periods of high relative humidity at the summit then.

Summit skies will be predominantly clear at least through the next 3 nights. Some high clouds might start to be visible from the NE late on Sunday, early Monday, advected over from the SW. They will break and thin through the rest of this forecast period.

Precipitable water will linger close to 1.5 mm tonight, it is likely to settle in the 1 to 1.5 mm range on Saturday night and linger close to 1 and 1.5 respectively for Sunday and Monday nigh. It is projected to increase afterward (3 to 4 mm).

Observing conditions will be rather poor tonight as wind at the summit have picked up and are likely to remain moderate through this evening and tonight, possibly decreasing in time. Expect seeing variability on Saturday night as well and more average conditions for the remaining nights, although upper level shear might become a little more of an issue then.

Not much is changed since the morning forecast, if not for some adjustment to the wind speed... The current weather scenario is dominated by a strong surface high passing north of the Hawaiian's chain. This will ensure atmospheric stability but will also thight the gradients and increase surface wind speed at the summit through tomorrow. Meanwhile an upper level low to the East of the State keeps moving toward the islands and it is projected to vear to the North at first, leaving the islands on its left, by Sunday, and possibly retrogradely continue its march westward afterward. As a result some high clouds might be advected over the area from the SW and so some moisture. Upper level shear will also increase then and therefore negatively affect free atmospheric turbulence. Other than that, this feature is not expected to greatly affect the summit weather.
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 Jun 22 - 8 PM0-20Clear0 / 02.5E/15-300.8-1.21-1.5
Sat Jun 23 - 2 AM0-20Clear0 / 01E/15-250.6-11.25-1.75
2 PM0-20Clear0 / 07NE/15-25NaN1.5-2.5
8 PM0-20Clear0 / 02NE/15-250.6-11-1.5
Sun Jun 24 - 2 AM0-20Clear0 / 01NE/15-250.45-0.851-1.5
2 PM0-20Clear0 / 07ENE/15-25NaN1.5-2.5
8 PM0-20Clear0 / 01.5ENE/15-250.4-0.81-1.5
Mon Jun 25 - 2 AM10-307-80 / 01ENE/10-200.45-0.850.9-1.3
2 PM10-307-80 / 06.5ENE/10-20NaN1-2
Tue Jun 26 - 2 AM20-406-80 / 01E/10-200.45-0.851.25-1.75
2 PM20-406-80 / 07E/5-15NaN2-3
Wed Jun 27 - 2 AM20-407-80 / 00.5SE/10-200.4-0.82.5-3.5
2 PM10-307-80 / 07SE/5-15NaN3-4
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 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
Mon Jun 25 - Tue Jun 26 19:14 20:28 4:21 5:35 N/A 4:51 97 16 56.0 -19 07
Tue Jun 26 - Wed Jun 27 19:14 20:28 4:22 5:36 17:56 5:37 99 17 47.4 -20 42
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 25 June 2018.
Additional Information
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This message is also available at the MKWC road conditions page.
NWS Hawaiian Islands Synoptic Discussion and Guidance
Honolulu National Weather Service Data and Products