Current Conditions
Temp7.9 C
RH49 %
WindNNE 13 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
4 PM HST Friday 13 July (0200 UTC Saturday 14 July) 2018
Warning(s)
Chance for fog and light rain
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for fog through the night; precipitation is possible but unlikely. Scattered mid/upper-level clouds will continue to pass over/near the summit through the night, moving eastward.
Summary of Key Meteorological Variables
Summit temperatures will be near 4 C this evening and 2.5 C tonight and tomorrow morning. Winds will be light and variable, with seeing near 0.5-0.6 arcseconds. Precipitable water is expected to exceed 4 mm through the night.
Discussion
The tradewind inversion is expected to lift toward 10 thousand feet tonight, then vanish completely, allowing the atmosphere to become fairly saturated for at least Saturday night. This will raise the stakes on fog, high humidity and light rain at the summit for tonight and especially tomorrow night. There is a good chance that the inversion will restregthen again, diminishing this risk for Sunday and Monday night, but the inversion may weaken again, which could raise the stakes again for Tuesday night. Daytime clouds could turn extensive for the weekend, taper a bit on Monday only to pick up again for Tuesday and Wednesday.

Scattered mid/high clouds will continue to pass over through tonight then will begin to shift to the northern skies and become more widespread for tomorrow night. In addition, there is good chance that thicker mid/summit-level clouds will develop in the area and/or drift in from the east during the latter night. The bulk of the thick clouds will shift off toward west by early Sunday evening, but patches of mid-level clouds may still linger for that night and the high clouds to the north will persist well into next week. There is also a possibility for another round of summit-level clouds will move in from the east for Tuesday night.

Precipitable water is expected to linger near or exceed 4 mm through the next 5 nights.

Relatively calm skies will prevail in the free atmosphere likely allowing for better than average seeing for tonight. While winds aloft will weaken and take on a predominately laminar westerly flow probably for the remainder of the forecast period an influx of summit-level moisture may contribute to poor/bad seeing for tomorrow night and perhaps Sunday night. There is a good chance that seeing will improve as the air mass dries out during the latter night and especially for Monday night. However, another round of summit-level moisture may degrade and/or contribute to more variable seeing for Tuesday night.

Not much is changed since this morning forecast... Although the low-level ridge will continue to sit to the far north of the state probably well into next week, the redevelopment of a fairly strong/broad tropical upper-trospheric trough (TUTT) to the NW will begin to destabilize the air mass and deepen the incoming low-level cloud flow over the next 24 hours. This will likely help raise the inversion toward 10 thousand feet over the course of tonight and eventually allow the atmosphere to turn fairly saturated, raising the stakes on fog, high humidity, light rain and extensive cloud cover at the summit for tomorrow night. Fortunately, the TUTT is expected to lift subtly northward, which could help stabilize the air mass, rebuild the inversion and reduce the risk for moisture at the summit for Sunday and especially Monday night. Still mid/high clouds transported via the sub-tropical jet along the southern fringe of the TUTT could remain an issue during that time. There is also a possiblity that the TUTT will shift southward again, while a tropical wave/storm moves in from the east around the middle part of next week. Although the TUTT/STJ will play a significant role in the dismantling of this storm as it approaches the area, moisture/instability surrounding this tropical feature combined with instability associated with the TUTT could produce another round of fog/rain at the summit for Tuesday night.
WRF Astronomical Observing Quality Guidance
Cloud Cover and Precipitable Water Analyses
MK CN² Profiles
5 Day Forecast Summary (Graphical Trend)
HST Cloud Fog/Precip Temp Wind Seeing PW
Cover (%) Height (km) Probability (%) (Celcius) (Dir/MPH) (Arcseconds) (mm)
Fri Jul 13 - 8 PM40-609-1010 / 04NNE/0-100.35-0.654-8
Sat Jul 14 - 2 AM40-608-1020 / 03WSW/0-100.5-0.84-8
2 PM40-606-940 / 106WNW/0-10NaN4-8
8 PM60-804-770 / 202NE/0-100.6-18-12
Sun Jul 15 - 2 AM70-904-780 / 301.5ESE/5-150.5-0.98-12
2 PM70-904-750 / 205ESE/5-15NaN8-12
8 PM60-806-830 / 01.5E/5-150.5-0.98-12
Mon Jul 16 - 2 AM40-606-820 / 01ENE/5-150.4-0.86-10
2 PM20-406-710 / 07ENE/10-30NaN4-8
Tue Jul 17 - 2 AM10-306-710 / 02ENE/10-300.4-0.84-6
2 PM40-604-740 / 07ENE/10-20NaN4-6
Wed Jul 18 - 2 AM40-604-760 / 202.5E/15-250.5-0.94-6
2 PM60-804-770 / 408E/15-25NaN4-6
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
Sun Jul 15 - Mon Jul 16 19:14 20:26 4:30 5:42 N/A 21:56 15 10 47.8 10 07
Mon Jul 16 - Tue Jul 17 19:14 20:26 4:30 5:43 N/A 22:41 24 11 42.1 5 31
Tue Jul 17 - Wed Jul 18 19:13 20:26 4:31 5:43 N/A 23:24 34 12 34.0 0 43
Wed Jul 18 - Thu Jul 19 19:13 20:25 4:31 5:43 N/A 0:04 45 13 24.2 -4 00
Thu Jul 19 - Fri Jul 20 19:13 20:25 4:32 5:44 N/A 0:44 56 14 13.5 -8 27
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 16 July 2018.
Additional Information
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