Current Conditions
Temp3.9 C
RH7 %
WindSE 0 mph
Mauna Kea Observatories Forecast
5 PM HST Tuesday 19 August (0300 UTC Wednesday 20 August) 2014
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 4 C this evening and 3.5 C tomorrow morning. Winds will be ESE, light at 5 to 10 mph, with seeing around 0.6 arcseconds. Precipitable water is expected to be in the 0.8-1 mm range for the night.
The tradewind inversion will continue to cap low-level moisture near 6 thousand feet and ensure the summit remains dry and stable through tomorrow afternoon. Deep low-level moisture moving into the area is expected to dismantle the inversion and increase the risk for fog and light rain at the summit between late Wednesday afternoon and early Thursday afternoon. The inversion is slated to recover again early Thursday evening, which will help to dry out the summit-level air mass for the remainder of the forecast period. Daytime clouds will be minimal and short-lived for today, but could pick up for Wednesday and Thursday, only to taper again for Friday and Saturday.

Skies will remain predominately clear of high clouds throughout the forecast period. However, there is a possibility for summit and perhaps mid-level clouds in the area for Wednesday night.

Precipitable water is expected to linger near 0.9-1 mm for tonight, increase to 4+ mm for tomorrow night, decrease again to the 1.5 mm for most of Thursday and Thursday and the rest of this forecast period.

Building mid-level turbulence is expected to gradually degrade seeing through tonight and probably contribute to poor/bad seeing for tomorrow night and perhaps early Thursday evening. Seeing is slated to improve as this turbulence subsides during the latter night and should settle in near better than average values as calm skies prevail for Friday and Saturday night.

Nothing is changed since this morning forecast... The mid/low-level ridge will continue to sit to the north of the state and promote steady large-scale subsidence in the area through the week. Unfortunately, remnants of a tropical cyclone is slated to briefly pass through the Big Island, bringing deep moisture, minor instability and mid-level turbulence to the summit mainly for tomorrow night. The former two will help dismantle the inversion, saturate the air mass below 16-18 thousand feet and significantly increase the risk for fog and rain at the summit for that night. The turbulence will likely degrade seeing and may be felt as early as tonight and persist into Thursday evening. Fortunately, the dry/stable conditions and clear skies enforced by the ridge will prevail prior to and after the passing of this remnant storm. In fact, very dry air out ahead of and directly behind this old storm should allow PW to linger near 0.9-1 mm for tonight and most of Thursday night, respectively. Seeing is also expected to settle back down toward 0.5 arcseconds once calmer skies associated with an upper-level ridge builds in overhead for Friday and Saturday 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)
Tue Aug 19 - 8 PM0-20Clear0 / 04E/5-100.45-0.750.9-1.3
Wed Aug 20 - 2 AM0-5Clear0 / 03.5ESE/5-100.4-0.70.8-1.2
2 PM0-5Clear0 / 08SSE/5-15NaN1-2
8 PM10-304-650 / 103.5SSE/5-150.7-1.12-3
Thu Aug 21 - 2 AM60-804-680 / 302.5SSE/5-150.8-1.24-8
2 PM60-804-660 / 107ENE/5-10NaN4-8
8 PM40-604-610 / 03NNE/5-150.5-0.94-5
Fri Aug 22 - 2 AM0-10Clear0 / 02.5NNE/5-150.4-0.81.5-2
2 PM0-20Clear0 / 09ENE/10-20NaN1-2
Sat Aug 23 - 2 AM0-5Clear0 / 04ENE/5-150.3-0.71-1.5
2 PM0-20Clear0 / 09E/5-15NaN1.5-2.5
Sun Aug 24 - 2 AM0-5Clear0 / 03.5ENE/5-150.3-0.72-3
2 PM0-20Clear0 / 09NNE/5-15NaN1.5-2
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 Aug 19 - Wed Aug 20 18:56 20:04 4:47 5:54 1:57 N/A 22 6 05.5 18 11
Wed Aug 20 - Thu Aug 21 18:56 20:03 4:48 5:55 2:46 N/A 15 6 55.5 17 19
Thu Aug 21 - Fri Aug 22 18:55 20:02 4:48 5:55 3:36 N/A 9 7 44.2 15 41
Fri Aug 22 - Sat Aug 23 18:54 20:01 4:48 5:55 4:25 17:04 4 8 31.7 13 24
Sat Aug 23 - Sun Aug 24 18:53 20:00 4:49 5:56 5:14 17:44 1 9 18.0 10 34
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Wednesday 20 August 2014.
Additional Information
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