Maunakea Observatories Forecast
6 AM HST (1600 UTC) Monday 02 December 2024
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Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while scattered high clouds pass mainly along the northern skies throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 8.5 C this afternoon and 3.5 C for the night. Winds will be from the SW at 5-15 mph for today, switching to a more NW direction and easing through the night. Seeing will be near 0.4-0.5 arcseconds, while precipitable water is expected to be in the 2-2.5 mm range for the night.
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Discussion
A well-defined tradewind inversion will continue to cap low-level moisture primarily near 6 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.
Scattered high clouds will continue to pass mainly along the northern skies over the next 2 nights, but cloud cover should not exceed 30% for any prolong periods during that time. Predominately clear skies will prevail for Wednesday night, but there is a chance that a light band of cirrus will slip through the area for Thursday night and a patch of scattered high cloud may pass along the northern skies around Friday evening.
Precipitable water is expected to linger in the 2-2.5 mm range for tonight, settle into 1.5-2 mm range for the next 2 nights, and perhaps dip a touch more to 1.25-1.5 mm for Thursday and Friday night.
Light winds at and above the summit, combined with a stable/calm air mass will allow seeing to settle in around 0.4-0.5 arcseconds probably through early Wednesday evening. However, strengthening southerly winds in the 10-20 thousand feet layer may increase boundary layer turbulence and contribute to a degradation in seeing through Wednesday night and likely through most of Thursday night. Winds near summit-level are set to subside by Friday morning as relatively deep/laminar westerly flow builds in aloft, which should help to improve seeing again for that night.
A flat mid/surface ridge will continue to stretch across most of the Pacific and sit over the state, before expanding meridionally to the NE beginning Wednesday. Nevertheless, the ridge will promote steady/strong large-scale subsidence in the area, which will easily maintain a distinct inversion near 6 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. While the westerly jet has strengthened and deepend considerably over the last week or two, it will sustain a rather zonal orientation further to the north of the state until a relatively weak short-wave trough passes further to the north around Friday. As a result, calm skies and light winds will prevail in the free atmosphere, and combined with a stable air mass and weak winds embedded in the ridge will allow seeing to settle in around 0.4-0.5 arcseconds probably through early Wednesday evening. Mid-level winds are set to strengthen and switch to a more southerly direction as the ridge expands to the NE ahead of the approaching SWT between late Wednesday evening and Friday morning. This may contribute to an increase in boundary layer turbulence that may degrade seeing during that period. Winds are set to subside again the ridge sags southward and weakens in response to the passing of the SWT later that night. The SWT is not expected to impact the stability of the air mass during its passage, while the easing of mid-level winds should help to improve seeing for Friday night.
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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 Dec 02 - 2 PM | 0-20 | 9-10 | 0 / 0 | 8.5 | SW/5-15 | NaN | 2-3 |
| 8 PM | 10-30 | 9-10 | 0 / 0 | 3.5 | W/5-15 | 0.4-0.5 | 2-2.5 |
| Tue Dec 03 - 2 AM | 10-30 | 9-10 | 0 / 0 | 3.5 | NW/0-10 | 0.4-0.5 | 2-2.5 |
| 2 PM | 0-20 | 9-10 | 0 / 0 | 9 | NNW/0-10 | NaN | 2-3 |
| 8 PM | 10-30 | 9-10 | 0 / 0 | 4.5 | E/0-10 | 0.35-0.45 | 1.5-2 |
| Wed Dec 04 - 2 AM | 10-30 | 9-10 | 0 / 0 | 4.5 | SSE/0-10 | 0.35-0.45 | 1.5-2 |
| 2 PM | 0-20 | Clear | 0 / 0 | 10 | S/5-15 | NaN | 2-3 |
| 8 PM | 0-10 | Clear | 0 / 0 | 4.5 | S/10-20 | 0.4-0.6 | 1.5-2 |
| Thu Dec 05 - 2 AM | 0-10 | Clear | 0 / 0 | 4 | SSW/10-20 | 0.45-0.75 | 1.5-2 |
| 2 PM | 0-20 | Clear | 0 / 0 | 8 | WSW/15-30 | NaN | 2-3 |
| Fri Dec 06 - 2 AM | 0-20 | 9.5-10 | 0 / 0 | 2 | W/10-20 | 0.5-0.8 | 1-2 |
| 2 PM | 0-20 | Clear | 0 / 0 | 7 | SSW/5-15 | NaN | 1.5-2.5 |
| Sat Dec 07 - 2 AM | 0-10 | Clear | 0 / 0 | 1.5 | WSW/5-15 | 0.375-0.625 | 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 |
| Mon Dec 02 - Tue Dec 03 |
17:51 |
19:00 |
5:24 |
6:32 |
N/A |
19:16 |
5 |
18 29.2 |
-28 12 |
| Tue Dec 03 - Wed Dec 04 |
17:52 |
19:00 |
5:25 |
6:33 |
N/A |
20:15 |
10 |
19 26.6 |
-26 45 |
| Wed Dec 04 - Thu Dec 05 |
17:52 |
19:00 |
5:25 |
6:34 |
N/A |
21:15 |
17 |
20 22.8 |
-23 49 |
| Thu Dec 05 - Fri Dec 06 |
17:52 |
19:01 |
5:26 |
6:34 |
N/A |
22:15 |
26 |
21 17.0 |
-19 36 |
| Fri Dec 06 - Sat Dec 07 |
17:52 |
19:01 |
5:26 |
6:35 |
N/A |
23:14 |
36 |
22 09.1 |
-14 20 |
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Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Monday 02 December (0300 UTC Tuesday 3 December) 2024.
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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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