Current Conditions
Temp3.5 C
RH15 %
WindNE 14 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Friday 14 June (0300 UTC Saturday 15 June) 2019
Warning(s)
Chance for fog/high humidity
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for periods of fog and high humidity, mainly during the second half of the night; precipitation is not expected and skies will remain predominately clear.
Summary of Key Meteorological Variables
Summit temperatures will be near 4.5 C for this evening and 3.5 C tomorrow morning. Winds will be light and from the NNE, with seeing near 0.4-0.45 arcseconds. Precipitable water is expected to be in the 2-3 mm range for the first half of the night and 3-4 mm range for the second half.
Discussion
The inversion is expected to briefly weaken/lift toward 10-11 thousand feet, which may increase the risk for short-lived fog and high humidity at the summit for tonight; precipitation is not expected. The inversion is set to reover near 7-8 thousand feet late tomorrow morning, ensuring the summit the summit remains dry and stable for the remainder of the forecast period. Some minor afternoon clouds are possible for tomorrow, then will become minimal and short-lived again for Sunday and early part of next week.

Skies will remain predominately clear of organized high clouds through at least Sunday night. There is a chance that thin high clouds will fill in from the south and east on Monday, which may increase cloud cover a bit mainly for Tuesday night.

Precipitable water is expected to start out near 2 mm for early this evening, but increase toward 4 mm by the end of the night and for Saturday night, then settle in primarily near 3.5 mm for the following 3 nights.

Relatively calm skies with light/uniform NE flow will prevail in the free atmosphere, allowing seeing to remain near 0.4-0.5 arcseconds over the next 3 nights. An increase in free atmospheric turbulence and light mid-level shear may degrade seeing toward more average-like values for Monday and Tuesday night.

Subtle changes have been made to the PW forecast...A deep ridge to the NW will gradually shift eastward over the weekend, before slipping off toward the NE as the tropical upper-tropospheric trough redevelops over the state during the early part of next week. Nevertheless, the ridge will still promote strong/steady large-scale subsidence, which for the most part will help maintain a well-defined inversion primarily near 7-8 thousand feet and ensure a dry/stable summit-level air mass throughout most of the forecast period. The only exception could be as a weak/dissipating tropical wave scrapes the southern portion of the Big Island later tonight. Moisture and remanant instability associated with this wave could briefly weaken/lift the inversion toward 10-11 thousand feet and increase the risk for periods of fog/high humidity at the summit, though the odds are slim. Nevertheless, calm skies embedded to the ridge should allow for good to excellent seeing to prevail over much of the weekend. There is a chance that upper-level turbulence and perhaps mid-level shear will increase as the TUTT reforms in the area, which may result in a minor degradation in seeing during the early part of next week.
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 Jun 14 - 8 PM0-5Clear20 / 04.5NNE/0-100.3-0.52-3
Sat Jun 15 - 2 AM0-5Clear30 / 03.5NNE/0-100.35-0.553-4
2 PM0-20Clear10 / 08.5NNE/5-15NaN3-5
8 PM0-5Clear0 / 03.5NE/5-150.35-0.553.5-4.5
Sun Jun 16 - 2 AM0-5Clear0 / 03NE/5-150.35-0.553.5-4.5
2 PM0-20Clear0 / 08E/5-15NaN3-5
8 PM0-5Clear0 / 02.5SSE/5-150.3-0.53-4
Mon Jun 17 - 2 AM0-5Clear0 / 01.5SSE/10-200.35-0.553-4
2 PM0-209.5-100 / 06.5SE/10-20NaN3-5
Tue Jun 18 - 2 AM0-209.5-100 / 01SE/10-200.5-0.73-4
2 PM0-209-100 / 06.5SE/10-20NaN3-5
Wed Jun 19 - 2 AM20-409-100 / 01ESE/5-150.5-0.83-4
2 PM40-609-100 / 07.5NE/10-20NaN3-5
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
Sat Jun 15 - Sun Jun 16 19:12 20:26 4:19 5:33 17:41 5:25 99 16 50.5 -20 09
Sun Jun 16 - Mon Jun 17 19:12 20:26 4:19 5:33 18:38 6:15 100 17 46.2 -22 08
Mon Jun 17 - Tue Jun 18 19:13 20:27 4:19 5:33 19:32 N/A 99 18 41.9 -22 58
Tue Jun 18 - Wed Jun 19 19:13 20:27 4:19 5:34 20:24 N/A 96 19 36.6 -22 37
Wed Jun 19 - Thu Jun 20 19:13 20:27 4:20 5:34 21:13 N/A 91 20 29.6 -21 12
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 17 June 2019.
Additional Information
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