Current Conditions
Temp6.7 C
RH41 %
WindNE 16 mph
Mauna Kea Observatories Forecast
4 PM HST Monday 15 July (0200 UTC Tuesday 16 July) 2019
Cloud Cover and Fog/Precipitation Forecast
The summit will be mostly dry and stable through tonight.
Summary of Key Meteorological Variables
Summit temperatures will be near 3 C this evening and 2.5 C tonight. Winds will be from the NNE at 15-25 mph during the first half of the night, decreasing some as the night progresses. PW will linger close to 3 mm. Observing conditions will be average but variable.
The tradewind inversion will continue to promote a mostly stable environment throughout most of this forecast period. Nevertheless bouts of moisture will be advected over the area from the East and from the South, on and off from early tomorrow and through Thursday. This will casuse the inversion to weaken some and lift a bit allowing for extended daytime clouds and possible episodes of high relative humidity/fog mostly during the early hours of the night from tomorrow through Thursday. A drying trend will follow afterward.

Summit skies will be predominantly clear today. Mid level clouds, building up on the East, are expected to approach the summit tomorrow and possibly result in extensive daytime clouds and lingering fog/humidity for Tuesday evening. Mid level clouds could be an issue through Thursday as they will continue to pop and building up on the SE of Big Island and increase moisture at the summit on an off through then. A clearing is expected afterward.

Precipitable water will linger close to 3 mm tonight and range between 2 and 2.5 mm on Tuesday night. It will likely exceed the 4 mm threshold on Wednesday and Thursday night to then start slowly decreasing and linger close to 4 mm mm on Friday night.

Orbserving conditions will be average but variable tonight and tomorrow night. They will degrade on Wednesday and Thursday night as surface winds pick up and moisture might linger at the summit during the evening/night hours. An improvement is expected starting on Friday.

No changes since the morning forecast.. The high pressure ridge, located north of the islands, will continue to promote a mostly stable environment through most of this forecast period. Nevertheless a weak trough is expected to develop into a retrograde upper level low, which will approach the islands from the E and quickly move eastward, from tomorrow throught Thursday. This feature will advect some mid level moisture over the summit, intermittently, resulting, from tomorrow, in extensive daytime clouds, lingering fog in the evening hours and an overall increase in PW and relative humidity through the end of the working week. A slight improvement is expected from Friday. Also, tighter pressure gradients will increase surface winds at the summit for Wednesday and Thursday. As a result observing conditions, still holding tonight and Tuesday night, might be less than average and variable on the following two nights, to then start improving again on Friday as overall summit conditions improve.
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 Jul 15 - 8 PM0-20Clear0 / 03.NNE/15-250.5-0.83-4
Tue Jul 16 - 2 AM0-20Clear0 / 02.5NNE/10-200.4-0.72.5-3.5
2 PM40-603.5-4.540 / 07ENE/5-15NaN4-6
8 PM0-20Clear0 / 03NE/5-150.4-0.83.5-4.5
Wed Jul 17 - 2 AM0-20Clear0 / 02.5SSE/5-150.35-0.752-2.5
2 PM30-503.5-4.560 / 08SSE/10-20NaN4-6
8 PM20-403.5-4.550 / 03.5ESE/15-250.7-1.14-6
Thu Jul 18 - 2 AM20-403-540 / 03E/15-250.6-14-6
2 PM50-703-570 / 07.5E/15-25NaN4-6
Fri Jul 19 - 2 AM20-403.5-4.560 / 02.5E/15-250.6-14-8
2 PM20-403.5-4.520 / 07ESE/10-20NaN4-6
Sat Jul 20 - 2 AM0-20Clear10 / 02NNE/5-150.4-0.84-6
2 PM0-20Clear0 / 08N/5-15NaN2-3
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 Jul 15 - Tue Jul 16 19:14 20:26 4:30 5:42 18:18 5:52 100 19 18.6 -22 52
Tue Jul 16 - Wed Jul 17 19:14 20:26 4:30 5:42 19:07 N/A 100 20 12.1 -21 48
Wed Jul 17 - Thu Jul 18 19:13 20:26 4:31 5:43 19:53 N/A 98 21 03.8 -19 45
Thu Jul 18 - Fri Jul 19 19:13 20:25 4:31 5:43 20:35 N/A 94 21 53.3 -16 52
Fri Jul 19 - Sat Jul 20 19:13 20:25 4:32 5:44 21:14 N/A 89 22 40.7 -13 19
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Tuesday 16 July 2019.
Additional Information
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