Maunakea Observatories Forecast
630 AM HST (1630 UTC) Monday 07 July 2025
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Warning(s)
Moderate/strong winds
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while light cirrus gradually dissipates overhead through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 7 C this afternoon, 2 C this evening and 1.5 C tomorrow morning. Winds will be from the east at 25-40 mph for today and 30-45 mph for the night. Seeing will exceed 1 arcsecond, while precipitable water is expected to linger near 0.8-0.9 mm for the night.
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Discussion
A distinct tradewind inversion will continue to cap low-level moisture primarily near 7 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.
Light cirrus will continue to build in from the south over the next 6-12 hours and gradually dissipate over the summit area through Tuesday night. Mostly clear skies will prevail for the following 3 nights.
Precipitable water is set to linger near 0.8-0.9 mm through Tuesday night, then settle in around 0.7 mm for the following 3 nights.
Deep easterly winds are expected to stir up boundary layer turbulence and contribute to poor/bad seeing through Wednesday night. While deep easterly winds will persist below 25 thousand feet into the weekend, winds near summit-level are set to taper significantly and light westerly flow will prevail in the free atmosphere. This, combined with a dry/stable air mass, should allow for excellent seeing on Thursday and Friday night.
The mid/surface ridge will continue to sit to the north of the state probably well into next week, while an upper-level ridge will prevail overhead and to the east, before dissipating in response to an upper-level low developing to the north around mid-week. Nonetheless, steady/strong subsidence will persist near the state, which will easily maintain a well-defined tradewind inversion near 7 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. PW will also benefit from the subsidence and presense of the upper-level ridge, likely settling in near 0.7-0.8 mm (or less) during that time. Unfortunately, the upper-level ridge will also help augment deep easterly flow below 20 thousand feet, which will stir up boundary layer turbulence and contribute to poor/bad seeing over the next 3 nights. Winds in the lower half of the atmosphere are set to subside with the dissipation of the upper-level ridge by Thursday morning, which should allow seeing to settle back in around 0.4 arcseconds for the following 2 nights.
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5 Day Forecast Summary (Graphical Trend)
| HST |
Cloud |
Fog/Precip |
Temp |
Wind |
Seeing |
PW |
| Cover (%) |
Height (km) |
Probability (%) |
(Celsius) |
(Dir/MPH) |
(Arcseconds) |
(mm) |
| Mon Jul 07 - 2 PM | 40-60 | 9.25-10 | 0 / 0 | 7 | E/25-40 | NaN | 0.8-1.2 |
| 8 PM | 20-40 | 9.5-10 | 0 / 0 | 2 | E/30-45 | 1-2 | 0.7-0.9 |
| Tue Jul 08 - 2 AM | 10-30 | 9.5-10 | 0 / 0 | 1.5 | E/30-45 | 1-2 | 0.8-1 |
| 2 PM | 0-20 | 9.25-10 | 0 / 0 | 7 | E/25-40 | NaN | 0.8-1.2 |
| 8 PM | 0-20 | 9.5-10 | 0 / 0 | 2 | E/20-35 | 0.8-1.6 | 0.7-0.9 |
| Wed Jul 09 - 2 AM | 0-20 | 9.5-10 | 0 / 0 | 2 | E/20-35 | 0.8-1.6 | 0.7-0.9 |
| 2 PM | 0-20 | Clear | 0 / 0 | 8 | E/15-30 | NaN | 0.8-1.2 |
| 8 PM | 0-10 | Clear | 0 / 0 | 3.5 | E/15-30 | 0.7-1.1 | 0.6-0.8 |
| Thu Jul 10 - 2 AM | 0-10 | Clear | 0 / 0 | 3 | E/10-20 | 0.55-0.85 | 0.6-0.8 |
| 2 PM | 0-20 | Clear | 0 / 0 | 10 | E/5-15 | NaN | 0.8-1.2 |
| Fri Jul 11 - 2 AM | 0-10 | Clear | 0 / 0 | 4.5 | NE/0-10 | 0.3-0.5 | 0.6-0.8 |
| 2 PM | 0-20 | Clear | 0 / 0 | 9.5 | SSE/5-15 | NaN | 0.8-1.2 |
| Sat Jul 12 - 2 AM | 0-10 | Clear | 0 / 0 | 3.5 | ESE/0-10 | 0.3-0.5 | 0.6-0.8 |
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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 Jul 07 - Tue Jul 08 |
19:15 |
20:28 |
4:26 |
5:39 |
N/A |
3:56 |
94 |
17 04.9 |
-28 35 |
| Tue Jul 08 - Wed Jul 09 |
19:15 |
20:28 |
4:27 |
5:40 |
17:35 |
4:50 |
98 |
18 01.8 |
-29 05 |
| Wed Jul 09 - Thu Jul 10 |
19:15 |
20:28 |
4:27 |
5:40 |
18:29 |
5:47 |
100 |
18 59.5 |
-28 06 |
| Thu Jul 10 - Fri Jul 11 |
19:15 |
20:28 |
4:27 |
5:40 |
19:19 |
N/A |
99 |
19 56.5 |
-25 37 |
| Fri Jul 11 - Sat Jul 12 |
19:14 |
20:27 |
4:28 |
5:41 |
20:06 |
N/A |
97 |
20 51.6 |
-21 47 |
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Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Monday 07 July (0300 UTC Tuesday 8 July) 2025.
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Additional Information
For public road conditions and snow report message please call (808) 935-6268.
This message is also available at the MKWC road conditions page.
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