Current Conditions
Temp4.9 C
RH32 %
WindNNE 0 mph
Mauna Kea Observatories Forecast
5 PM HST Monday 15 September (0300 UTC Tuesday 16 September) 2014
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, but there is a possibility for light isolated patches of cirrus in the area.
Summary of Key Meteorological Variables
Summit temperatures will be near 4.5 C, with light NE winds and seeing around 0.6-0.65 arcseconds. Precipitable water is expected to be in the 2.5-3.5 mm range for the first half of the night and 2-3 mm range for the second half.
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. Some afternoon clouds are possible for today, but will become minimal and short-lived for the remainder of the forecast period.

There is a possibility for lingering patches of isolated high clouds in the area for tonight, and another larger patch is slated to spread in from the southwest and pass over/near (mainly along the northern skies) the summit during the next 2 nights. These clouds will shift off toward the northeast early Thursday morning, leaving relatively clear skies for the remainder of the forecast period.

Precipitable water is expected to linger near 2-2.5 mm through the next 5 nights.

A patch of low-level turbulence is slated to linger over/near the summit, contributing to poorer than average seeing through Wednesday evening. This turbulence is slated to subside early Thursday morning, allowing seeing to improve toward 0.4-0.5 arcseconds for the next 2 nights.

Little change since the morning forecast...The eastern edge of mid-level ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area through the week. This will be more than enough to maintain the tradewind inversion near 8-9 thousand feet, keep low-level moisture to a minimum, negate the instability associated with a decaying front or the tropical upper-tropospheric trough (TUTT) and ensure a dry/stable summit-level air mass throughout the forecast period. However, the dissipating front could still produce minor low-level turbulence in the area and contribute to poorer than average seeing over the next 2-3 nights. The TUTT will also gain access to patches of high clouds and stream it over and particularly along the northern skies during that time. Clearer/calmer skies is expected to build back over the summit as the front totally falls apart and the TUTT shifts further westward during the second half of the forecast period.
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 Sep 15 - 8 PM0-209-100 / 04.5NNE/0-100.55-0.752.5-3.5
Tue Sep 16 - 2 AM0-209.5-100 / 04.5NNE/0-100.55-0.652-3
2 PM10-309.5-100 / 010ESE/0-10NaN2-3
8 PM20-409-100 / 05.5N/0-100.6-0.72-3
Wed Sep 17 - 2 AM10-309-100 / 05NE/0-100.6-0.71.75-2.25
2 PM10-309-100 / 010S/0-10NaN2-3
8 PM20-409-100 / 05NW/0-100.55-0.651.75-2.25
Thu Sep 18 - 2 AM10-309-100 / 04.5W/0-100.5-0.61.75-2.25
2 PM0-20Clear0 / 010WSW/5-15NaN2-3
Fri Sep 19 - 2 AM0-10Clear0 / 04WSW/5-150.35-0.552-3
2 PM0-20Clear0 / 09W/5-15NaN2-3
Sat Sep 20 - 2 AM0-10Clear0 / 03.5NNW/0-100.35-0.551.5-2.5
2 PM0-20Clear0 / 09NNE/0-10NaN2-3
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 Sep 15 - Tue Sep 16 18:33 19:38 4:56 6:01 23:52 N/A 46 5 52.0 18 14
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
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 16 September 2014.
Additional Information
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