Current Conditions
Temp4.0 C
RH11 %
WindNNE 14 mph
RoadClosed
Mauna Kea Observatories Forecast
5 PM HST Tuesday 22 October (0300 UTC Wednesday 23 October) 2019
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will be predominantly clear, dry and stable throughout tonight.
Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C this evening and 4 C tonight. Winds will be from the NE at 5-15mph but with possible times of very low/dead wind. Seeing will be average/good, with possible spikes due to dying wind. Precipitable water is expected to linger close to 2 mm.
Discussion
The tradewind inversion is expected to remain in place and strong enough to maintain the summit predominantly stable and mostly dry throughout most of this forecast period. Nevertheless the inversion might lift and weaken at times, particularly on Friday, in response to weakening fronts passing by to the North of the islands. Some moisture, advected from the south, might climb up the summit then and raise the odds for short lived episodes of high relative humidity on Friday and Saturday, when some daytime clouds might also be forming.

The summit skies will be mostly clear today. Some cirri might be visible along the south and western horizon early tomorrow morning and might near through tomorrow, obscuring only a small portion of the summit sky. A second bout of high clouds is expected early on Friday, approaching from the south. These clouds will thicken some in time and obscure at least half of the summit sky on Friday and Saturday.

Precipitable water will linger close to 2 mm tonight. It is projected to increase and near the 4 mm threshold, lingering in the 3 to 5 mm range on Wednesday night, to then increase soe more and exceed it throughout the rest of this forecasting period.

Observing conditions will be average to good tonight and tomorrow night with a possible added variability due to conditions of dying winds which might cause seeing to spike at times. Conditions might degrade some as moisture in the atmosphere and some high clouds might get in the way of observing from Thursday and onward.

No changes since the morning forecast... The current weather scenario continues to be domimated by a high pressure system located to the northeast of the State and its associated ridge, which will continue to promote mostly stable and dry airmasses over the islands throughout most of this forecast period. Nevertheless, the model projects two weakening fronts to yet again swing by to the North of the Hawaiian Islands: the first one to approach and stall north of the area late on Wednesday and through Thursday, and a second one to approach during the weekend. These systems are likely to not affect much the weather at the summit if not for an increase in mid level moisture advected over, which will result in a somewhat higher PW, and by some passing high clouds drawn over the area from the SSW, mostly from late Thursday through Friday and Saturday. As the inversion will weaken and lift at times then, daytime clouds will be possible on Friday. Short lived episodes of high relative humidity are possible from late on Thursday through Friday night and part of Saturday.
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)
Tue Oct 22 - 8 PM0-20Clear0 / 03.5NE/5-150.4-0.71.75-2.25
Wed Oct 23 - 2 AM0-20Clear0 / 04NE/5-150.5-0.81.75-2.25
2 PM0-20Clear0 / 010NNE/0-10NaN2.5-3.5
8 PM10-307-80 / 04NNE/5-150.4-0.73-4
Thu Oct 24 - 2 AM20-407-80 / 04N/0-100.4-0.73-5
2 PM0-20Clear0 / 010.5SW/0-10NaN3-4
8 PM20-407-80 / 04NW/5-150.4-0.83.5-4.5
Fri Oct 25 - 2 AM30-507-830 / 03W/5-150.4-0.84-6
2 PM50-705.5-760 / 58SW/5-15NaN4-6
Sat Oct 26 - 2 AM50-705.5-740 / 53WSW/5-150.6-13-5
2 PM20-406-750 / 57.5NW/5-15NaN4-6
Sun Oct 27 - 2 AM10-307-830 / 03E/0-100.5-0.94-6
2 PM0-20Clear0 / 08N/5-15NaN3-5
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 Oct 22 - Wed Oct 23 18:02 19:07 5:05 6:10 1:38 N/A 29 9 54.5 16 12
Wed Oct 23 - Thu Oct 24 18:02 19:07 5:06 6:11 2:40 N/A 19 10 50.9 11 45
Thu Oct 24 - Fri Oct 25 18:01 19:06 5:06 6:11 3:43 N/A 10 11 46.1 6 32
Fri Oct 25 - Sat Oct 26 18:01 19:06 5:06 6:11 4:45 16:40 4 12 40.5 0 53
Sat Oct 26 - Sun Oct 27 18:00 19:05 5:07 6:12 5:47 17:24 1 13 34.7 -4 49
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Wednesday 23 October 2019.
Additional Information
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This message is also available at the MKWC road conditions page.
NWS Hawaiian Islands Synoptic Discussion and Guidance
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