Current Conditions
Temp2.5 C
RH73 %
WindWSW 0 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Thursday 11 August (0300 UTC Friday 12 August) 2022
High humidity
Cloud Cover and Fog/Precipitation Forecast
There is a small/moderate risk for periods of fog as humidity lingers near 60-80% for the night; precipitation is unlikely. Isolated to scattered to the southwest may drift into/near the summit area through the night
Summary of Key Meteorological Variables
Summit temperatures will be near 2 C this evening and 1.5 C tomorrow morning. Winds will be light and variable, with seeing near 0.7-0.8 arcseconds. Precipitable water is expected to exceed 4 mm for the night.
While the tradewind inversion will remain fairly well-defined near 7-8 thousand feet throughout the forecast period, there patches of mid-level moisture moving through area will keep summit-level humidity near 60-80% and could allow for short-lived fog at the summit over the next 2 nights; precipitation is unlikely. This moisture will move out of the area through Friday night, ensuring the summit remains dry/stable over the weekend and early part of next week. Extensive daytime clouds are possible through tomorrow, then will become minimal/short-lived over the weekend and early part of next week.

Isolated to scattered mid/upper-level clouds to the south and west and may occasionally drift overhead mainly through tomorrow evening. These clouds will shift further westward by Saturday morning, leaving mostly clear skies for the weekend. There is a chance that patches of high clouds will fill in from the west for Monday night.

Precipitable water is expected to exceed 4 mm through tomorrow evening, but will trend down thereafter, settling in near 1 mm by the end of Saturday night and for Sunday night. There is a possibility that it will increase toward 2 mm for Monday night.

Persistent mid-level moisture and slowly decaying low-level turbulence will likely contribute to poor seeing for tonight and perhaps early tomorrow evening. Seeing will improve as the air mass stabilizes/dries through the latter night and will eventually settle in near 0.4-0.5 arcseconds for the following 3 nights. There is a chance that seeing will dip below 0.4 arcseconds for the early part of next week.

Very little change since the morning forecast...Although the mid/surface ridge will persist to north of the state and promote steady large-scale subsidence across most of the east/central Pacific, a weak tropical disturbance passing to the south will continue to mid-level moisture near the summit area into Friday night. This moisture will likely be responsible for periods of high humidity (near 60-80%) and perhaps short-lived fog at the summit over the next 2 nights. Seeing and PW will also negatively respond to this influx of moisture, and there is a possibility that this disturbance will help create a secondary inversion (by cooling of the air mass near 15 thousand feet) just above the summit during this time. The disturbance and all of its associated moisture are set to shift off to the west by sunrise Saturday, which will ensure dry/stable summit summit conditions over the weekend and early part of next week. Seeing and PW are expected to respond to the departure of this moisture and eventually settle in near 0.45-0.5 arcseconds and 1 mm, respectively, for Saturday and especially Sunday night. There is a chance that an influx of upper-level moisture/clouds will push PW back toward 2 mm for Monday night. Seeing, on the other hand, could dip below 0.4 arcseconds as calmer skies prevail in the free atmosphere for that night.
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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Thu Aug 11 - 8 PM10-306-940 / 52WSW/0-100.6-14-6
Fri Aug 12 - 2 AM10-306-835 / 51.5SW/0-100.6-0.94-6
2 PM40-604-840 / 106SSW/0-10NaN4-6
8 PM0-205.5-725 / 52SSE/0-100.5-0.84-6
Sat Aug 13 - 2 AM0-205.5-620 / 52.5SSE/0-100.475-0.7253-5
2 PM0-20Clear0 / 09SE/0-10NaN2-3
8 PM0-10Clear0 / 04ENE/0-100.425-0.6751.5-2
Sun Aug 14 - 2 AM0-10Clear0 / 04NE/0-100.4-0.61-1.5
2 PM0-20Clear0 / 010NE/5-15NaN1-2
Mon Aug 15 - 2 AM0-5Clear0 / 04.5SE/0-100.35-0.550.8-1.2
2 PM0-20Clear0 / 010SE/5-15NaN1-2
Tue Aug 16 - 2 AM10-309-100 / 04.5ESE/0-100.3-0.51.5-2.5
2 PM10-309-100 / 09SSE/5-15NaN2-4
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
Thu Aug 11 - Fri Aug 12 19:02 20:10 4:44 5:52 19:02 6:53 100 21 55.5 -18 37
Fri Aug 12 - Sat Aug 13 19:01 20:10 4:44 5:52 19:48 N/A 97 22 52.6 -12 53
Sat Aug 13 - Sun Aug 14 19:01 20:09 4:45 5:53 20:29 N/A 92 23 45.8 -6 37
Sun Aug 14 - Mon Aug 15 19:00 20:08 4:45 5:53 21:07 N/A 85 0 36.0 -0 15
Mon Aug 15 - Tue Aug 16 18:59 20:07 4:45 5:53 21:43 N/A 76 1 24.5 5 54
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 12 August 2022.
Additional Information
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