Current Conditions
Temp6.0 C
RH17 %
WindNE 18 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Thursday 02 July (0300 UTC Friday 3 July) 2020
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain clear, dry and stable for the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 5.5 C this evening and 5 C tomorrow morning. Winds will be from the north at 5-15 mph, with seeing near 0.35-0.4 arcseconds. Precipitable water is expected to be in the 1.5-2 mm range for the night.
Discussion
A distinct tradewind inversion will continue to cap low-level moisture at or below 9 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Skies overhead will remain predominately clear through the next 5 nights.

Precipitable water is expected to linger near 1.75-2 mm for the next 3 nights, then slip toward 1 mm or less for Sunday and Monday night.

Relatively light/laminar flow will prevail in the free atmosphere, which will help minimize free atmospheric turbulence and allow for good/excellent seeing throughout most of the forecast period. The odds are higher for excellent seeing mainly over the next 2 nights and again early next week.

No change since the morning forecast...A fairly well-defined mid/low-level ridge will continue to sit to the NE of the state and promote steady/strong large-scale subsidence in the area well into next week. This subsidence will easily maintain a distinct inversion at or below 8 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. In the upper atmosphere, a tropical upper tropospheric trough (TUTT) will continue to stretch from the west coast and out to Guam, but will also remain further displaced to the north (of the state) and quite weak during this time. This will not only minimize upper-level instability in the area, but allow predominately clear/calm skies to prevail in the free atmosphere as the sub-tropical jet also remains quite weak and indistinct. As a result, seeing should continue to linger near 0.4-0.45 arcseconds throughout most of the forecast period. There is a strong possibility that seeing will dip below 0.4 arcseconds at any time, but particularly over the next 2 nights and again for the early part of next week.

Please Note: There will be no forecast tomorrow, July 3, in observance of Independence Day; the normal forecast schedule will resume on July 6.
HST CC (%) CLD HGT (km) Fog Prob (%) Prcp Prob (%) Temp (C) Wind (dir/mph) Seeing (asec) PW (mm)
---------------------------------------------------------------------------------------------------------------------------------------
07/02/2020 2000 0-5 Clear 0 0 5.5 0/5-15 0.3-0.5 1.5-2
07/03/2020 0200 0-5 Clear 0 0 5 0/5-15 0.25-0.45 1.5-2
07/03/2020 1400 0-20 Clear 0 0 9.5 315/0-10 NaN 1.5-2.5
07/03/2020 2000 0-5 Clear 0 0 4 330/0-10 0.25-0.45 1.5-2
07/04/2020 0200 0-5 Clear 0 0 3.5 300/0-10 0.3-0.5 1.75-2.25
07/04/2020 1400 0-20 Clear 0 0 7.5 150/0-10 NaN 2-3
07/04/2020 2000 0-5 Clear 0 0 2.5 135/0-10 0.35-0.55 1.5-2
07/05/2020 0200 0-5 Clear 0 0 1.5 135/0-10 0.35-0.55 1.25-1.75
07/05/2020 1400 0-20 Clear 0 0 6.5 60/5-15 NaN 1-2
07/06/2020 0200 0-5 Clear 0 0 1.5 60/0-10 0.3-0.5 0.8-1.2
07/06/2020 1400 0-20 Clear 0 0 7 90/5-15 NaN 1-2
07/07/2020 0200 0-5 Clear 0 0 3 90/5-15 0.275-0.475 0.6-1
07/07/2020 1400 0-20 Clear 0 0 9 120/5-15 NaN 0.8-1.2
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)
Thu Jul 02 - 8 PM0-5Clear0 / 05.5N/5-150.3-0.51.5-2
Fri Jul 03 - 2 AM0-5Clear0 / 05N/5-150.25-0.451.5-2
2 PM0-20Clear0 / 09.5NW/0-10NaN1.5-2.5
8 PM0-5Clear0 / 04NNW/0-100.25-0.451.5-2
Sat Jul 04 - 2 AM0-5Clear0 / 03.5WNW/0-100.3-0.51.75-2.25
2 PM0-20Clear0 / 07.5SSE/0-10NaN2-3
8 PM0-5Clear0 / 02.5SE/0-100.35-0.551.5-2
Sun Jul 05 - 2 AM0-5Clear0 / 01.5SE/0-100.35-0.551.25-1.75
2 PM0-20Clear0 / 06.5ENE/5-15NaN1-2
Mon Jul 06 - 2 AM0-5Clear0 / 01.5ENE/0-100.3-0.50.8-1.2
2 PM0-20Clear0 / 07E/5-15NaN1-2
Tue Jul 07 - 2 AM0-5Clear0 / 03E/5-150.275-0.4750.6-1
2 PM0-20Clear0 / 09ESE/5-15NaN0.8-1.2
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
Sun Jul 05 - Mon Jul 06 19:15 20:28 4:25 5:39 19:50 N/A 98 20 12.5 -23 25
Mon Jul 06 - Tue Jul 07 19:15 20:28 4:26 5:39 20:40 N/A 94 21 08.4 -20 58
Tue Jul 07 - Wed Jul 08 19:15 20:28 4:26 5:39 21:25 N/A 88 22 00.8 -17 33
Wed Jul 08 - Thu Jul 09 19:15 20:28 4:27 5:40 22:05 N/A 81 22 49.9 -13 27
Thu Jul 09 - Fri Jul 10 19:15 20:28 4:27 5:40 22:42 N/A 73 23 36.3 -8 55
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 3 July 2020.
Additional Information
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