Current Conditions
Temp7.2 C
RH29 %
WindE 11 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
730 AM HST (1730 UTC) Monday 08 August 2022
Increasing winds
Cloud Cover and Fog/Precipitation Forecast
The summit will remain clear, dry and stable through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 6 C this afternoon, -0.5 C this evening and -2 C tomorrow morning. Winds will be from the ESE at 10-20 mph for today, increasing to 15-30 mph for the night. Seeing will be near 0.8-0.9 arcseconds, while precipitable water is expected to be in the 2-2.5 mm range for the night.
A fairly well-defined inversion will continue to cap low-level moisture near 7-8 thousand feet and ensure a dry/stable summit-level air mass over the next 2 nights. An influx of deep tropical moisture is expected to erode the inversion, push summit-level humidity toward 90-100% and likely contribute to extensive fog, periods of rain/flurries and ice at the summit for Wednesday and probably Thursday night. The bulk of this moisture will begin to slide out of the area through Friday, which should help rebuild the inversion and reduce the risk for moisture at the summit for that night. Daytime clouds will be minimal and short-lived through Tuesday, but will turn extensive for Wednesday and Thursday, only to taper again for Friday and especially over the weekend.

Clear skies will prevail for at least tonight, but there is a chance that isolated/thin high clouds will begin to fill in from the south for tomorrow night. Thicker more widespread clouds are set to build along the far southern skies during the latter night and will probably fill in overhead, contributing to extensive cloud cover or even overcast skies for at least Wednesday night. These clouds will begin to shift westward through Thursday night, leaving predominately clear skies for Friday night.

Precipitable water is expected to increase into the 2-2.5 mm range for tonight, trend back toward 1 mm through tomorrow night, only to jump to 8-10 mm for Wednesday and Thursday night. There is a very good chance that it will dip toward 2 mm through Friday night.

An increase in boundary layer turbulence, combined with low-level thermodynamic turbulence will contribute to poor seeing for tonight. The boundary layer turbulence is set to strengthen, further degrading seeing for tomorrow night and an influx of deep moisture will probably result in inoperable conditions (and bad seeing) for Wednesday and Thursday night. There is good chance that calmer skies and dry/stable conditions will allow for a dramatic improvement in seeing through Friday night.

The mid/surface ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence throughout much of the NE Pacific through the week. Initially this subsidence will be enough to maintain a fairly distinct inversion near 7-8 thousand feet and ensure a dry/stable summit-level air mass over the next 2 nights. Unfortunately, a tropical wave 500+ km to the SE will begin tighten the wind gradient as it shifts eastward over the next 48 hours. This will lead to an increase in summit-level winds and boundary layer turbulence, contributing to poor/bad seeing over the next 2 nights. In addition, a tropical disturbance/storm is expected take shape as this wave passes to the south through tomorrow night. While the center of this disturbance is set to pass ~250 km to the state over the next 2 nights, widespread/deep tropical moisture is projected to fill overhead by late Wednesday morning. This will probably contribute to a fairly saturated air mass, which will push summit-level humidity toward 90-100% and allow extensive fog, ice and/or light flurries/rain to plague the summit probably for the next 2 nights. The bulk of this moisture (and disturbance) is expected to slip west of the Big Island by sunrise Friday, which should help to dramatically improve conditions 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)
Mon Aug 08 - 2 PM0-20Clear0 / 06ESE/10-20NaN2-4
8 PM0-5Clear0 / 0-0.5ESE/15-300.6-12-2.5
Tue Aug 09 - 2 AM0-5Clear0 / 0-2ESE/15-300.7-1.12-2.5
2 PM0-20Clear0 / 04E/20-35NaN2-4
8 PM0-209.5-100 / 0-1E/25-400.8-1.41.5-2
Wed Aug 10 - 2 AM0-209.5-100 / 0-1E/25-400.9-1.51-1.5
2 PM80-1004-695 / 605SE/15-30NaN8-12
8 PM60-804-795 / 650.5SE/15-301-28-12
Thu Aug 11 - 2 AM60-804-995 / 75-0.5SE/10-201-28-12
2 PM80-1004-995 / 656ESE/10-20NaN8-12
Fri Aug 12 - 2 AM40-604-575 / 251SSE/5-150.8-1.68-12
2 PM20-404-4.540 / 107ESE/0-10NaN4-8
Sat Aug 13 - 2 AM0-20Clear10 / 03ESE/0-100.5-0.82-4
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
Mon Aug 08 - Tue Aug 09 19:04 20:13 4:42 5:51 N/A 3:29 89 18 40.3 -27 41
Tue Aug 09 - Wed Aug 10 19:03 20:12 4:43 5:51 17:10 4:37 96 19 48.1 -26 27
Wed Aug 10 - Thu Aug 11 19:03 20:11 4:43 5:52 18:09 5:46 99 20 53.8 -23 18
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
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Monday 08 August (0300 UTC Tuesday 9 August) 2022.
Additional Information
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