Maunakea Observatories Forecast
5 PM HST Friday 17 January (0300 UTC Saturday 18 January) 2025
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Warning(s)
Fog, ice and high humidity
Moderate/strong winds
Cloud Cover and Fog/Precipitation Forecast
There is a moderate/high risk for periods of fog, ice and high humidity throughout the night; precipitation is unlikely. Patches mid/upper-level clouds will continue to pass along the NE skies throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near -4 C, with winds from the NW at 30-45 mph for the night. Seeing and PW are expected to linger near or exceed 1 arcsecond and 4 mm, respectively, through the night.
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Discussion
Moisture and instability passing through/near the area keep the inversion rather indistinct, which could allwo for periods of fog, ice and high humidity for tonight; precipitation is unlikely. The inversion is set to recover again by late Saturday morning, becoming well-defined near 5-6 thousand feet and allowing dry/stable conditions to return to the summit over the remainder of the weekend and early next week. Daytime clouds will become minimal and short-lived again for the weekend and early next week.
Patches of mid/upper-level will continue to pass along the northeastern skies, before shifting eastward leaving clear skies during the second half of tonight. However, more scattered high clouds may build in from the NW and slip along the northeastern skies again over the remainder of the weekend. There is also a chance that scattered high clouds will skirt by along the northern skies for Monday night, then will sag southward, perhaps passing overhead for Tuesday night. Still, cloud cover should not exceed 30% for any prolong period through much of the next 5 nights.
Precipitable water is expected to linger near 4 mm for much of tonight, then trend toward 3 mm through Saturday night, dip to 1 mm for Sunday, briefly/subtly increase to 1.5 mm for Monday night, then drop back to 1 mm for Tuesday night.
A mixture of boundary layer turbulence and moderate/strong free atmospheric turbulence will contribute to bad seeing probably through much of the weekend. There is a chance that the free atmospheric turbulence will actually subside by early Sunday morning, but seeing is not expected to improve much until summit-level winds subside on Monday. Lighter summit-level winds, combined with a stable air mass and laminar NNW flow in the free atmosphere could help seeing to settle in around 0.5-0.6 arcseconds for Monday night and perhaps toward 0.4 arcseconds for Tuesday night.
No change since the morning forecast...A sharp trough and reflective mid/surface low to the east of the state will continue to destabilize the air mass, while relatively deep patches of moisture/clouds scrape the Big Island for another 12 hours. This may help keep the inversion rather indistinct and could allow for more periods of fog, ice and high humidity at the summit through tonight. In addition, a tight wind gradient bordering the trough and a new deep ridge gradually building in west will contribute to moderate/strong winds at the summit and thus bad seeing probably through the weekend. Strong free atmospheric turbulence (likely in the form of gravity waves) will also disrupt seeing mainly through Sunday morning. On the other hand, the eastward advancement of the deep ridge will reinstill strong large-scale subsidence in the area around sunrise tomorrow. This will help rebuild a rather distinct inversion near 5-6 thousand feet by late that morning and ensure a dry/stable summit-level air mass for the remainder of the forecast period. Summit-level winds are set to drop below 20 mph, once the center of the ridge begins to shift into the area late Monday, which could allow for an improvement in seeing for that night and especially Tuesday 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) |
| Fri Jan 17 - 8 PM | 0-20 | 5-7 | 75 / 15 | -4 | NW/30-45 | 1-2 | 4-6 |
| Sat Jan 18 - 2 AM | 0-20 | 5-6 | 65 / 15 | -4 | NW/30-45 | 1-2 | 3.5-4.5 |
| 2 PM | 0-20 | Clear | 0 / 0 | 2 | NNW/25-40 | NaN | 2-4 |
| 8 PM | 10-30 | 7-8 | 0 / 0 | -3 | N/20-35 | 1-2 | 2.5-3.5 |
| Sun Jan 19 - 2 AM | 0-20 | 7-8 | 0 / 0 | -2.5 | N/20-35 | 0.8-1.6 | 2.5-3.5 |
| 2 PM | 0-20 | 7-8 | 0 / 0 | 3 | NNE/20-35 | NaN | 1.5-2.5 |
| 8 PM | 0-20 | 7-8 | 0 / 0 | -2 | NNE/25-40 | 0.7-1.3 | 1-1.5 |
| Mon Jan 20 - 2 AM | 0-20 | Clear | 0 / 0 | -1 | NNE/20-35 | 0.7-1.3 | 0.8-1.2 |
| 2 PM | 0-20 | 8-9 | 0 / 0 | 5 | NNE/15-30 | NaN | 1-2 |
| Tue Jan 21 - 2 AM | 0-20 | 8-9 | 0 / 0 | 0 | NNW/10-20 | 0.4-0.8 | 1-2 |
| 2 PM | 0-20 | 8-9 | 0 / 0 | 6 | NNW/10-20 | NaN | 1-2 |
| Wed Jan 22 - 2 AM | 0-20 | 8-9 | 0 / 0 | 1 | WNW/5-15 | 0.3-0.6 | 0.8-1.2 |
| 2 PM | 0-20 | 8-9 | 0 / 0 | 5 | W/5-15 | NaN | 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 Jan 20 - Tue Jan 21 |
18:16 |
19:24 |
5:43 |
6:50 |
0:04 |
N/A |
53 |
13 39.7 |
-12 53 |
| Tue Jan 21 - Wed Jan 22 |
18:17 |
19:24 |
5:43 |
6:50 |
0:54 |
N/A |
44 |
14 24.5 |
-17 45 |
| Wed Jan 22 - Thu Jan 23 |
18:18 |
19:25 |
5:43 |
6:50 |
1:46 |
N/A |
35 |
15 11.8 |
-21 57 |
| Thu Jan 23 - Fri Jan 24 |
18:18 |
19:25 |
5:42 |
6:49 |
2:41 |
N/A |
26 |
16 02.4 |
-25 18 |
| Fri Jan 24 - Sat Jan 25 |
18:19 |
19:26 |
5:42 |
6:49 |
3:38 |
N/A |
18 |
16 56.3 |
-27 33 |
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Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 20 January 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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