Current Conditions
Temp6.0 C
RH29 %
WindS 0 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Friday 22 March (0300 UTC Saturday 23 March) 2019
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will be clear, dry and stable through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 4 C this evening and 3 C tomorrow morning. Winds will be from the WNW at 0-10 mph. Seeing will be average (0.55-0.65) and somewhat variable through the night. Precipitable water will range between 1 and 1.5 mm.
Discussion
The tradewind inversion will continue to ensure mostly dry and stable conditions at the summit through Saturday. The inversion is projected to weaken and lift some on Sunday. It is not expected to vanish altogheter, but moisture from the low levels could slip up the summit increasing the chances for short-lived daytime clouds from Sunday onward. The inversion might remain rather elevated and weak just ahead of another mid/upper level disturbance.

Summit skies will be predominantly clear tonight. Mid-high clouds might be visible along the northern horizon Saturday and Sunday, but the bulk of them should remain North of the Big Island and summit skies will only be partially interested. More clear skies will follow.

Precipitable water will range between 1 and 1.5 mm tonight. It will be close to 1.5 mm on Saturday night and close to 2 on Sunday night. It will further increase to the 2 to 3 mm range on Monday night and be close to 3 on Tuesday night.

Observing conditions will be average tonight, with seeing expected to be in the 0.55-0.65 average range. The ground layer is likely to be quite calm as turbulence is concerned throughout most of this forecast period. Variability and degrading might come from the upper levels as shear aloft increases through Sunday, worsening as times goes by from tonight through the end of the weekend. A calmer free atmosphere is possible on Monday and Tuesday night.

Not much is changed since the morning forecast... The sub-tropical high pressure ridge will continue to promote large scale subsidence throughout most of this forecast period ensuring overall dry and stable conditions. Nevertheless the lingering shallow front North of the State will continue to drift southeastward, and the limited amount of low level moisture carryied by it is likely to get caught in the tradewind flow and slowly be advected backward over the island chain and the Big Island, from Sunday and onward. This moisture is likely to linger in the area, destabilizing a little the inversion, which is going to weaken and lift some, allowing, at times, some moisture to reach the summit. PW will increase a tad and daytime clouds will be more likely from Sunday. Also an increase in shear aloft is expected from today and through the weekend, which will add variability to the otherwise average/good observing conditions. A mid/upper level trough will pass North of the State mid of the coming week and will push another front close to the islands, likely destabilizing some the airmasses.
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)
Fri Mar 22 - 8 PM0-10Clear0 / 04NNW/0-100.5-0.80.8-1.2
Sat Mar 23 - 2 AM0-10Clear0 / 03WNW/0-100.4-0.71-1.5
2 PM0-20Clear0 / 08SW/0-10NaN1-2
8 PM0-10Clear0 / 03WNW/0-100.5-0.81-1.5
Sun Mar 24 - 2 AM10-307.5-80 / 01.5NNW/0-100.5-0.91.25-1.75
2 PM20-407-80 / 07WSW/0-10NaN1.5-2.5
8 PM10-307-80 / 01.5SW/0-100.5-0.91.5-2.5
Mon Mar 25 - 2 AM0-20Clear0 / 00.5WSW/5-150.6-11.5-2.5
2 PM0-20Clear0 / 06WSW/5-15NaN1.5-2.5
Tue Mar 26 - 2 AM0-20Clear0 / 0-1W/5-150.5-0.92-3
2 PM0-20Clear0 / 06.5W/10-20NaN1.5-2.5
Wed Mar 27 - 2 AM0-20Clear0 / 00WNW/15-250.4-0.82-3
2 PM20-403.5-4.50 / 07W/15-25NaN2.5-3.5
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
Sun Mar 24 - Mon Mar 25 18:43 19:47 5:08 6:13 22:28 N/A 76 16 07.0 -17 07
Mon Mar 25 - Tue Mar 26 18:43 19:48 5:07 6:12 23:24 N/A 67 17 01.0 -19 51
Tue Mar 26 - Wed Mar 27 18:43 19:48 5:06 6:11 0:18 N/A 57 17 54.6 -21 30
Wed Mar 27 - Thu Mar 28 18:44 19:48 5:06 6:10 1:10 N/A 47 18 47.5 -22 05
Thu Mar 28 - Fri Mar 29 18:44 19:49 5:05 6:09 1:59 N/A 37 19 39.2 -21 38
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 25 March 2019.
Additional Information
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This message is also available at the MKWC road conditions page.
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