Current Conditions
Temp4.5 C
RH8 %
WindNW 7 mph
Mauna Kea Observatories Forecast
5 PM HST Wednesday 01 July (0300 UTC Thursday 2 July) 2015
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for fog through the night; skies will remain predominately clear.
Summary of Key Meteorological Variables
Summit temperatures will be near 3 C this evening and 2.5 C tomorrow morning. Winds will be light and from the SW, with seeing around 0.6-0.65 arcseconds. Precipitable water is expected to be in the 3.5-4.5 mm range for the night.
Although the tradewind inversion will remain fairly well-defined near 6-8 thousand feet through the next 5 nights, an influx of mid-level moisture toward 50-70% over the next 3 nights (particularly tomorrow night). Still, the odds on fog and precipitation will remain quite low during this period and the summit will steer free of moisture over the weekend. Some afternoon clouds are possible over the next 3 days, then become minimal and short-lived for Saturday and Sunday.

Skies overhead will remain predominately clear of high clouds through the next 5 nights. However, there is a possibility that a patch of isolated/scattered high clouds will briefly pass along the southern skies around Friday evening.

Precipitable water is expected to increase toward 4-5 mm for the next 3 nights, then slip back to 2-3 mm for Saturday and Sunday night.

Persistent turbulence in the free atmosphere will likely keep seeing near 0.5-0.6 arcseconds over the next 5 nights. There is a possibility for slightly poorer and/or more variable seeing mainly over the next 2 nights and again for Saturday night.

No change since the morning forecast...The mid-level ridge will linger over the state as a trough persists to the north into the early part of next week. Although the ridge will still promote steady large-scale subsidence in the area and maintain a fairly well-defined tradewind inversion near 6-8 thousand feet during this time, an influx of moisture drawn toward the trough from the SE may help push summit-level humidity toward 50-70% and increase the risk for afternoon clouds over the next 3 days. Fortunately, the odds on fog (and especially precipitation) at the summit will remain quite low during this period, and the mid-level air mass is expected to dry out as the trough begins to weaken over the weekend. In addition, this trough will actually help supress the persistent sub-tropical jet off toward the south, which should allow for relatively clear skies throughout the forecast period. However, upper-level turbulence along the northern flank of the jet may contribute to more average-like seeing during this time.
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)
Wed Jul 01 - 8 PM0-5Clear15 / 03WSW/0-100.55-0.653.5-4.5
Thu Jul 02 - 2 AM0-5Clear10 / 02SW/0-100.55-0.753.5-4.5
2 PM60-804-560 / 156.5SSW/5-15NaN4-8
8 PM0-5Clear20 / 02SSW/0-100.5-0.74-6
Fri Jul 03 - 2 AM0-5Clear15 / 01.5SW/0-100.5-0.64-6
2 PM40-604-4.540 / 106.5WNW/0-10NaN4-8
8 PM0-20Clear15 / 01.5WNW/0-100.45-0.553.5-4.5
Sat Jul 04 - 2 AM0-10Clear10 / 01NW/5-150.5-0.63.5-4.5
2 PM0-20Clear0 / 07NNW/5-15NaN3-5
Sun Jul 05 - 2 AM0-5Clear0 / 02NNW/5-150.5-0.72-3
2 PM0-20Clear0 / 08NNW/5-15NaN2-4
Mon Jul 06 - 2 AM0-5Clear0 / 03NNE/5-150.45-0.652-3
2 PM0-20Clear0 / 08.5ENE/5-15NaN2-4
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
Wed Jul 01 - Thu Jul 02 19:15 20:29 4:23 5:37 18:48 6:40 100 19 01.1 -18 20
Thu Jul 02 - Fri Jul 03 19:15 20:29 4:24 5:37 19:42 N/A 98 20 00.6 -16 30
Fri Jul 03 - Sat Jul 04 19:15 20:29 4:24 5:38 20:34 N/A 93 20 59.5 -13 38
Sat Jul 04 - Sun Jul 05 19:15 20:29 4:24 5:38 21:24 N/A 85 21 57.0 -9 57
Sun Jul 05 - Mon Jul 06 19:15 20:28 4:25 5:38 22:11 N/A 76 22 53.1 -5 43
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Thursday 2 July 2015.
Additional Information
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