Current Conditions
Temp7.3 C
RH8 %
WindSE 12 mph
RoadOpen
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Monday 04 May 2015
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 8 C this afternoon, 3 C this evening and 2.5 C tomorrow morning. Winds will be light and from the east, with seeing near 0.45-0.5 arcseconds. Precipitable water is expected to be in the 0.7-0.9 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 9 thousand feet and ensure the summit steers free of moisture through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Summit skies will remain predominately clear through at least midnight tomorrow, but thin high clouds may start to fill in along the northern skies early Wednesday morning, with more scattered cirrus drifting in from the southwest later that night. The latter set may spread over the summit on Thursday, then slip eastward through that night, leaving predominately clear skies for much of Friday. However, more thin high clouds may fill in from due west early Saturday morning and could become more widespread over the weekend.

Precipitable water is expected to linger near 0.8 mm through Wednesday evening, then increase toward 1 mm as the night progesses, and probably settle in near 1.5-2 mm for Thursday and Friday night.

Relatively calm skies should allow for better than average seeing through at least tomorrow evening. However, an influx of mid and eventually upper-level turbulence will lkely contribute to slightly poorer than average seeing for Wednesday and especially Friday night. There is a possibility for some improvement in seeing as uniform winds set in aloft for Thursday night.

The mid/low-level ridge will continue to sit to the north of the state, promote strong/steady large-scale subsidence in the area and easily negate the a weak tropical upper-tropospheric trough (TUTT) to the west through the week. The subsidence will help maintain the tradewind inversion near 8-9 thousand feet and ensure the summit-level air mass remains dry and stable during this time. Predominately dry upper-level air will also prevail in the area, as the sub-tropical jet remains relatively weak and off toward the SE for the next 2-3 nights. This should allow PW and seeing to linger near 0.8 mm and 0.5 arcseconds, respectively, through at least tomorrow night. However, the jet is slated to strengthen, which will not only increase turbulence in the free atmosphere and thus degrade seeing, but could bring high clouds/moisture to the area over the following 3 days. Still, most of the clouds will be scattered, thin and quick moving, though they could become more widespread late in the weekend.
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)
Mon May 04 - 2 PM0-20Clear0 / 08E/0-10NaN0.7-0.9
8 PM0-5Clear0 / 03E/0-100.45-0.550.7-0.9
Tue May 05 - 2 AM0-5Clear0 / 02.5E/0-100.4-0.50.7-0.9
2 PM0-20Clear0 / 08ESE/0-10NaN0.7-0.9
8 PM0-5Clear0 / 02.5E/5-150.45-0.550.7-0.9
Wed May 06 - 2 AM0-209.5-100 / 02E/5-150.5-0.60.7-0.9
2 PM10-309-100 / 07.5SE/0-10NaN0.7-0.9
8 PM10-309-100 / 02.5E/0-100.55-0.750.7-0.9
Thu May 07 - 2 AM20-409-100 / 02ENE/0-100.55-0.750.8-1
2 PM20-409-100 / 06.5NE/0-10NaN1-1.5
Fri May 08 - 2 AM0-20Clear0 / 01NE/0-100.45-0.651.5-2
2 PM0-20Clear0 / 06N/0-10NaN1.5-2
Sat May 09 - 2 AM10-309-100 / 01NNE/5-150.5-0.91.5-2
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
Mon May 04 - Tue May 05 18:56 20:05 4:32 5:41 19:28 N/A 98 15 53.5 -16 41
Tue May 05 - Wed May 06 18:56 20:05 4:32 5:41 20:21 N/A 94 16 47.8 -18 13
Wed May 06 - Thu May 07 18:56 20:06 4:31 5:40 21:16 N/A 88 17 43.5 -18 50
Thu May 07 - Fri May 08 18:57 20:06 4:30 5:40 22:09 N/A 81 18 40.1 -18 26
Fri May 08 - Sat May 09 18:57 20:07 4:30 5:39 23:01 N/A 71 19 36.8 -17 00
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Monday 04 May (0300 UTC Tuesday 5 May) 2015.
Additional Information
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This message is also available at the MKWC road conditions page.
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