Current Conditions
Temp8.8 C
RH63 %
WindESE 13 mph
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Tuesday 16 September 2014
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, but there is a possibility for patches of thin high clouds along the northern skies through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 10.5 C this afternoon, 5 C this evening and 4.5 C tomorrow morning. Winds will be light and from the ENE, with seeing around 0.6-0.65 arcseconds. Precipitable water is expected to be in the 1.75-2.25 mm range for the night.
The tradewind inversion will continue to cap low-level moisture at or below 9 thousand feet and keep the mid/summit-level air mass dry and stable through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

There is a possibility for isolated thin high clouds along the northern skies over the next 2 nights and perhaps to the southeast for tomorrow night. Still, cloud cover should not exceed 20% for an prolong periods and clear skies will prevail for Thursday, Friday and Saturday night.

Precipitable water is expected to linger near 1.75-2.25 for the next 2 nights, briefly increase to 3-4 mm for Thursday night, then slip back to 2-2.5 mm for the following 2 nights.

Persistent low-level turbulence will likely contribute to slightly poorer than average seeing through Wednesday evening. This turbulence is slated to subside early Thursday morning and should allow seeing to settle in near 0.45-0.5 arcseconds probably for the remainder of the forecast period.

The eastern flank of the mid-level ridge will continue to sit to the north of the Islands for the next several days then shift further westward as a trough passes in the northern Pacific around Friday/Saturday. Nonetheless, the ridge will remain close enough to the state to promote strong/steady large-scale subsidence in the area and negate the affects of this passing trough as well as the tropical upper-tropospheric trough which is expected to linger to the northwest in the interim. This will ensure the summit will remain dry and stable with a well-defined tradewind inversion near 8-9 thousand feet throughout the forecast period. Still, there is a possibility that the TUTT will send isolated high clouds along the northern skies during the next 2 nights. A decaying weak front is also expected to linger over/near the Big Island, which could produce minor low-level turbulence and contribute to slightly poorer than average seeing during this time. Clearer/calmer skies will prevail as the TUTT as well as the front and its associated turbulence falls apart for the remainder of the forecast period. With the exception of slightly cooler summit-level temperatures, the aforementioned passing trough is not expected to have an impact on seeing, skies, or summit-level conditions during its passage.
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 Sep 16 - 2 PM0-209.5-100 / 010.5ENE/0-10NaN2-3
8 PM0-209-100 / 05NE/0-100.6-0.71.75-2.25
Wed Sep 17 - 2 AM0-209.5-100 / 04.5ENE/0-100.55-0.651.75-2.25
2 PM0-209.5-100 / 010ESE/0-10NaN2-3
8 PM0-209.5-100 / 05ENE/0-100.55-0.651.5-2
Thu Sep 18 - 2 AM0-209.5-100 / 04.5N/0-100.5-0.61.5-2
2 PM0-20Clear0 / 09SW/0-10NaN2-3
8 PM0-5Clear0 / 04WSW/0-100.45-0.553-4
Fri Sep 19 - 2 AM0-5Clear0 / 03.5W/0-100.4-0.53-4
2 PM0-20Clear0 / 08.5W/0-10NaN2-3
Sat Sep 20 - 2 AM0-5Clear0 / 03.5SSE/0-100.35-0.552-3
2 PM0-20Clear0 / 08.5W/0-10NaN2-3
Sun Sep 21 - 2 AM0-5Clear0 / 03S/0-100.4-0.61.5-2.5
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
Tue Sep 16 - Wed Sep 17 18:32 19:37 4:56 6:01 0:42 N/A 36 6 43.0 17 35
Wed Sep 17 - Thu Sep 18 18:31 19:36 4:57 6:01 1:32 N/A 28 7 32.5 16 08
Thu Sep 18 - Fri Sep 19 18:30 19:35 4:57 6:01 2:21 N/A 20 8 20.5 14 01
Fri Sep 19 - Sat Sep 20 18:29 19:34 4:57 6:02 3:10 N/A 13 9 07.2 11 19
Sat Sep 20 - Sun Sep 21 18:29 19:33 4:57 6:02 3:59 N/A 7 9 53.0 8 10
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Tuesday 16 September (0300 UTC Wednesday 17 September) 2014.
Additional Information
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