Maunakea Observatories Forecast
730 AM HST (1730 UTC) Tuesday 10 December 2024
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Warning(s)
Strong 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 4 C this afternoon, -1 C this evening and -2 C tomorrow morning. Winds will be from the NE at 25-40 mph for today, increasing to 40-60 mph and switching to a more easterly direction through the night. Seeing will exceed 1 arcsecond, while precipitable water is expected to start out near 1.5 mm, but will trend toward 1 mm or less as the night progresses.
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Discussion
A distinct tradewind inversion will continue to cap low-level moisture near 7-8 thousand feet and ensure a dry/stable summit-level air mass through at least Wednesday night. There is a possibility that deeper low-level clouds will pass through, lifting the inversion toward 12-13 and increase the risk for fog, ice and high humidity for Thursday and Friday night; precipitatio is unlikely. Daytime clouds will be minimal and short-lived through Thursday, but could turn extensive for Friday, only to taper again for the weekend.
Skies overhead will remain predominately clear for tonight and Friday night. There is a chance that high clouds passing along the southern skies will scrape the southern tip of the Big Island between early Wednesday morning and Friday morning. More high clouds may also build in from the NW for Saturday night.
Precipitable water is expected to start out near 1.5 mm for tonight, but will trend toward 1 mm as the night progresses. There is a good chance that PW will settle in near 1 mm over the remainder of the forecast period, though large spikes are possible for Thursday and Friday night.
Strong/deep NE winds are set to stir up boundary layer turbulence and contribute to poor/bad seeing at least Thursday night. There is a chance that seeing will begin to improve as winds subside through Friday night. Light winds throughout the atmosphere, combined with a stable air mass should allow seeing to settle back in near 0.4-0.5 arcseconds for Saturday night.
A deep mid/surface ridge to the NW, will continue to build eastward and promote steady/strong subsidence in the area through the week. This subsidence will easily maintain a well-defined inversion near 7-8 thousand feet and, combined with the absence of any instability or moisture, will ensure a dry/stable summit-level air mass over the next 2 nights. Unfortunately, an upper-level trough to the east of the state will briefly slow the eastward progression of the ridge, before depositing an upper-level low to the SE of the Big Island over the course of the day. This low will then progress westward before falling apart to the SW of the state over the early part of the weekend. While the trough/low will have no impact on the stability of the atmosphere in the area, latest model projections suggest that deeper clouds/moisture revolving around the low will scrape the southern tip of the Big Island between late Thursday afternoon and early Saturday morning. This could weaken/lift the inversion and increase the risk for fog, ice and high humidity at the summit for Thursday and Friday night. The inversion is set to recover as the low shifts subtly southward and off to the SW, allowing dry/stable summit conditions to return to the summit for Saturday night. In addition to the moisture, a tight wind gradient between the low and the ridge will sit over the state, which will result in deep/strong NE trades through at least Thursday night. This will stir up boundary layer turbulence and contribute to bad seeing over the next 3 nights. Seeing will begin to improve as winds begin to subside for Friday night and may eventually settle in near 0.4-0.5 arcsconds, once light easterlies set in throughout much of the atmosphere for Saturday 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) |
| Tue Dec 10 - 2 PM | 0-20 | Clear | 0 / 0 | 4 | NE/25-40 | NaN | 1.5-2.5 |
| 8 PM | 0-10 | Clear | 0 / 0 | -1 | ENE/35-50 | 1-3 | 1-1.5 |
| Wed Dec 11 - 2 AM | 0-10 | Clear | 0 / 0 | -2 | E/40-60 | 1-3 | 0.8-1.2 |
| 2 PM | 20-40 | 9-10 | 0 / 0 | 3 | E/40-60 | NaN | 1-1.5 |
| 8 PM | 10-30 | 9-10 | 0 / 0 | -1 | E/40-60 | 1-3 | 1-1.5 |
| Thu Dec 12 - 2 AM | 10-30 | 9-10 | 0 / 0 | -1 | E/35-50 | 1-3 | 1-1.5 |
| 2 PM | 10-30 | 9-10 | 25 / 5 | 4.5 | E/25-40 | NaN | 1-2 |
| 8 PM | 20-40 | 9-10 | 30 / 10 | 0.5 | E/25-40 | 1-2 | 1-1.5 |
| Fri Dec 13 - 2 AM | 20-40 | 9-10 | 30 / 10 | 0 | E/20-35 | 0.8-1.6 | 1-1.5 |
| 2 PM | 40-60 | 4-5 | 40 / 20 | 5 | E/15-30 | NaN | 4-8 |
| Sat Dec 14 - 2 AM | 0-10 | Clear | 10 / 0 | 1 | E/15-30 | 0.6-1.2 | 1-1.5 |
| 2 PM | 0-20 | Clear | 0 / 0 | 7 | E/5-15 | NaN | 1-2 |
| Sun Dec 15 - 2 AM | 20-40 | 9-10 | 0 / 0 | 1.5 | SE/0-10 | 0.3-0.6 | 1-1.5 |
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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 Dec 10 - Wed Dec 11 |
17:53 |
19:02 |
5:28 |
6:37 |
N/A |
3:08 |
79 |
1 32.1 |
11 49 |
| Wed Dec 11 - Thu Dec 12 |
17:54 |
19:03 |
5:29 |
6:38 |
N/A |
4:12 |
88 |
2 27.6 |
17 56 |
| Thu Dec 12 - Fri Dec 13 |
17:54 |
19:03 |
5:30 |
6:38 |
N/A |
5:19 |
95 |
3 26.9 |
23 01 |
| Fri Dec 13 - Sat Dec 14 |
17:55 |
19:03 |
5:30 |
6:39 |
16:10 |
6:26 |
99 |
4 30.0 |
26 38 |
| Sat Dec 14 - Sun Dec 15 |
17:55 |
19:04 |
5:31 |
6:39 |
17:08 |
7:32 |
100 |
5 35.3 |
28 25 |
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Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Tuesday 10 December (0300 UTC Wednesday 11 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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