Maunakea Observatories Forecast
6 AM HST (1600 UTC) Tuesday 08 July 2025
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Warning(s)
Moderate winds
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while light cirrus lingers and dissipates in the area throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 5.5 C this afternoon and 0.5 C for the night. Winds will be from the east at 25-40 mph for today, decreasing to 20-35 mph for the night. Seeing will exceed 1 arcsecond, while precipitable water is expected to be in the 0.7-0.9 mm range for the night.
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Discussion
A distinct tradewind inversion will continue to cap low-level moisture primarily near 7-8 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.
While light cirrus will continue to gradually dissipate over the summit area likely through Wednesday night, cloud cover will not exceed 25% for any prolong periods. Mostly clear skies will prevail for the following 3 nights.
Precipitable water is set to linger near 0.8 mm through Wednesday evening, settle in around 0.7 mm through Friday night, then increase subtly to 1 mm for Saturday night.
Deep easterly winds are expected to stir up boundary layer turbulence and contribute to poor/bad seeing through much of 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 good/excellent seeing on Thursday, Friday and much of Saturday 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 late Wednesday. Nonetheless, steady/strong subsidence will persist near the state, which will easily maintain a well-defined tradewind inversion near 7-8 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) into the weekend. 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 2 nights. Winds in the lower half of the atmosphere are set to subside with the dissipation of the upper-level ridge by Thursday morning. This should allow seeing to settle back in around 0.4-0.5 arcseconds over the remainder of the forecast period.
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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) |
| Tue Jul 08 - 2 PM | 10-30 | 9.25-10 | 0 / 0 | 5.5 | E/25-40 | NaN | 0.8-1.2 |
| 8 PM | 10-30 | 9.5-10 | 0 / 0 | 0.5 | E/20-35 | 0.8-1.6 | 0.7-0.9 |
| Wed Jul 09 - 2 AM | 0-20 | 9.5-10 | 0 / 0 | 0.5 | E/20-35 | 0.8-1.4 | 0.7-0.9 |
| 2 PM | 0-20 | 9.5-10 | 0 / 0 | 8 | E/20-35 | NaN | 0.8-1.2 |
| 8 PM | 0-20 | 9.5-10 | 0 / 0 | 3 | E/15-30 | 0.6-1 | 0.7-0.9 |
| Thu Jul 10 - 2 AM | 0-20 | 9.5-10 | 0 / 0 | 3 | E/10-20 | 0.5-0.8 | 0.6-0.8 |
| 2 PM | 0-20 | Clear | 0 / 0 | 10 | E/5-15 | NaN | 0.8-1.2 |
| 8 PM | 0-10 | Clear | 0 / 0 | 6 | NE/5-15 | 0.4-0.5 | 0.6-0.8 |
| Fri Jul 11 - 2 AM | 0-10 | Clear | 0 / 0 | 5.5 | ENE/5-15 | 0.35-0.45 | 0.6-0.8 |
| 2 PM | 0-20 | Clear | 0 / 0 | 10 | E/5-15 | NaN | 0.8-1.2 |
| Sat Jul 12 - 2 AM | 0-10 | Clear | 0 / 0 | 4 | E/5-15 | 0.3-0.5 | 0.6-0.8 |
| 2 PM | 0-20 | Clear | 0 / 0 | 8 | E/5-15 | NaN | 0.8-1.2 |
| Sun Jul 13 - 2 AM | 0-10 | Clear | 0 / 0 | 2 | ESE/0-10 | 0.375-0.625 | 0.8-1.2 |
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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 |
| 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 |
| Sat Jul 12 - Sun Jul 13 |
19:14 |
20:27 |
4:28 |
5:41 |
20:48 |
N/A |
93 |
21 44.3 |
-16 48 |
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Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Tuesday 08 July (0300 UTC Wednesday 9 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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