Current Conditions
Temp11.1 C
RH8 %
WindNE 0 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Thursday 22 June (0300 UTC Friday 23 June) 2017
Warning(s)
None
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 5.5 C this evening and 5 C tomorrow morning. Winds will be from the NNE at 5-15 mph, with seeing near 0.5-0.55 arcseconds. Precipitable water is expected to be in the 2-2.5 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture primarily near 7-8 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.

Skies overhead will remain predominately clear through at least Saturday evening. Bands of scattered high clouds building to the northwest and south may merge over the summit area, and could increase cloud cover toward 50% for Sunday night.

Precipitable water is expected to linger near 2-2.5 mm for the next 2 nights, increase to 3-4 mm for Saturday night, then slip back toward 2 mm for the following 2 nights.

Relatively calm skies and uniform light/moderate westerly flow aloft should allow seeing to settle in near 0.5 arcseconds for at least the next 3 nights. A increase in upper-level shear may degrade seeing toward 0.6 arcseconds for Sunday and Monday night.

No change since the morning forecast...The persistent mid and especially low-level ridge to the north of the state will continue to promote steady/strong large-scale subsidence in the area througout the forecast period. This subsidence will easily maintain a well-defined inversion primarily near 7-8 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. The tropical upper-tropospheric trough will continue to very gradually develop to the NW, before rapidly strengthening and digging to the SW around the early part of next week. The TUTT is not expected to affect the stability of the air mass throughout the forecast period, but its southern counterpart, the sub-tropical jet, main gain access to high clouds flowing out of the tropics and contribute to periods of extensive cloud cover as it digs southward on Monday. The STJ will also strengthen a bit, increasing shear in the free atmosphere, which may result in more average-like seeing for Sunday and Monday night. However, prior to that, relatively clear and calm skies should prevail as light/uniform westerly flow persists above the summit. This should allow seeing to settle in near 0.5 arseconds over the next 3 nights.
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)
Thu Jun 22 - 8 PM0-5Clear0 / 05.5NNE/5-150.45-0.652-2.5
Fri Jun 23 - 2 AM0-5Clear0 / 05NNE/5-150.4-0.62-2.5
2 PM0-20Clear0 / 010WNW/0-10NaN2-3
8 PM0-5Clear0 / 05N/0-100.35-0.552-2.5
Sat Jun 24 - 2 AM0-5Clear0 / 04WNW/0-100.4-0.62-2.5
2 PM0-20Clear0 / 09.5SW/0-10NaN2.5-3.5
8 PM0-5Clear0 / 04W/0-100.4-0.63-4
Sun Jun 25 - 2 AM0-209.5-100 / 03WSW/0-100.45-0.653.5-4.5
2 PM20-409-100 / 08SSW/0-10NaN2-4
Mon Jun 26 - 2 AM40-609-100 / 02.5S/5-150.45-0.751.5-2.5
2 PM60-808-100 / 07ESE/5-15NaN1.5-2.5
Tue Jun 27 - 2 AM60-808-90 / 02ESE/5-150.45-0.751.5-2.5
2 PM80-1008-90 / 07ENE/10-20NaN2-4
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
Thu Jun 22 - Fri Jun 23 19:14 20:28 4:20 5:35 5:19 18:04 1 5 28.0 18 03
Fri Jun 23 - Sat Jun 24 19:14 20:28 4:21 5:35 6:21 19:08 0 6 31.1 18 48
Sat Jun 24 - Sun Jun 25 19:14 20:28 4:21 5:35 N/A 20:10 3 7 33.7 18 13
Sun Jun 25 - Mon Jun 26 19:14 20:28 4:21 5:35 N/A 21:07 8 8 34.4 16 24
Mon Jun 26 - Tue Jun 27 19:14 20:28 4:22 5:36 N/A 21:59 15 9 32.0 13 34
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 23 June 2017.
Additional Information
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This message is also available at the MKWC road conditions page.
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