Current Conditions
Temp1.8 C
RH22 %
WindW 41 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Wednesday 22 May (0300 UTC Thursday 23 May) 2013
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will be clear, mostly dry and stable through the night.
Summary of Key Meteorological Variables
Summit temperature will be near 2 C this evening and 1 C tonight and tomorrow morning. Precipitable water will range between 2.5 and 3 mm through the night. Winds will be from the W at 10 to 25 mph. Seeing will average 0.55-0.6 arcsec.
Discussion
The tradewind inversion will continue to cap the low-level moisture below 8-9 thousand feet through most of this forecast period, maintaining the mid/summit-level air mass predominantly dry and stable. Nevertheless, because of the lingering moisture in the mid atmosphere and the daytime heating, moisture might increase and linger at the summit level particularly on Friday. Afternoon clouds are possible then. The inversion is projected to start lifting and weakening at the very end of this forecasting period, and increased moisture in the air mass might become and issue then.

Summit skies will be predominantly clear tonight. Some high patchy clouds are expected to approach the area from the SW and pass over the Big Island while moving northeastward on Thursday and Friday night. A clearing trend will follow thereafter. More high clouds will start being advected over from the East at the very end of the forecast period.

Precipitable water will be in the 2.5 to 3 mm range tonight and Thursday night. It is likely to exceed or linger close to 4 mm on Friday night, to then settle to a drier 1.5 to 2 mm range for the remaining two nights.

While winds at the surface will be decreasing through tonight, shear aloft are expected to increase late Thursday and through Friday, therefore expect slighlty poorer than average seeing for tonight and through Friday night. An improving trend is possible for the weekend nights.

Not much is changed since this morning forecast... The upper level trough/low North of the State is expected to move west and dissipate through today and tomorrow allowing the mid level ridge to strenghten and the air masses over the area to stabilize further. Meanwhile pressure gradients will release and winds at the surface will taper. Mostly stable conditions will persist through this forecast period, but lingering mid level moisture might create some minor issues on Friday. Observing conditions will also be slightly less than average because of a combination of tapering winds at the summit, still impacting boundary layer turbulence, and increasing shear aloft due to the STJ moving closer to the Big Island. Models project a trough to pass North of the State and an upper level low to develop East of the Hawaiian Islands at the beginning of the coming week. Although the main hawaiian islands will remain on the dry side of this system, it might destabilize the atmosphere then. More on this with next updates.
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 May 22 - 8 PM0-20Clear0 / 02WSW/20-350.5-0.82.5-3
Thu May 23 - 2 AM0-20Clear0 / 01W/10-250.4-0.72.5-3
2 PM20-407-80 / 07.5W/10-20NaN2.5-3.5
8 PM20-407-80 / 02.5NW/10-200.5-0.82.25-2.75
Fri May 24 - 2 AM20-407-80 / 01.5NW/5-150.45-0.752.5-3
2 PM0-20Clear30 / 08N/10-20NaN4-6
8 PM10-307-820 / 02N/10-200.4-0.84-6
Sat May 25 - 2 AM10-307-80 / 01.5N/10-200.5-0.94-6
2 PM0-20Clear0 / 07N/5-15NaN2-3
Sun May 26 - 2 AM0-20Clear0 / 01.5N/5-150.3-0.71.5-2
2 PM0-20Clear0 / 08NNE/5-15NaN1.5-2.5
Mon May 27 - 2 AM10-307-80 / 01NNW/5-150.4-0.81.5-2
2 PM10-306-840 / 06W/10-20NaN4-6
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 May 22 - Thu May 23 19:03 20:15 4:22 5:34 N/A 4:34 95 14 19.6 -15 29
Thu May 23 - Fri May 24 19:04 20:16 4:22 5:34 17:36 5:29 99 15 21.0 -18 32
Fri May 24 - Sat May 25 19:04 20:16 4:21 5:33 18:41 6:29 100 16 25.3 -20 23
Sat May 25 - Sun May 26 19:04 20:17 4:21 5:33 19:46 N/A 98 17 30.9 -20 47
Sun May 26 - Mon May 27 19:05 20:17 4:21 5:33 20:47 N/A 92 18 35.8 -19 41
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Thursday 23 May 2013.
Additional Information
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