Current Conditions
Temp3.2 C
RH65 %
WindE 7 mph
RoadOpen (4x4 only)
Mauna Kea Observatories Forecast
5 PM HST Tuesday 04 August (0300 UTC Wednesday 5 August) 2015
Warning(s)
Fog, high humidity and rain
Chance for convection
Cloud Cover and Fog/Precipitation Forecast
There is a high risk for fog, high humidity, mid/summit-level clouds and rain at the summit through the night; isolated convection may also pop up in the area during that time.
Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C, with winds from from the NE at 5-15 mph for the night. Seeing and PW are expected to exceed 1 arcsecond and 4 mm, respectively, through the night.
Discussion
After briefly strengthening overnight, the inversion is slated to breakdown as deep widespread tropical moisture and minor instability passes through the area over the next 3 nights (particularly the next two). Consequently, there is a high risk for fog, high humidity, rain at the summit and perhaps isolated convection in the area during that time. The inversion is slated to recover near 6 thousand feet around mid-day Friday, ensuring the summit-level air mass becomes dry and stable for the following 2 nights. Extensive daytime clouds are virtually expected through Thursday, then will become minimal and short-lived thereafter.

Thick broken clouds and pockets of deep convection will continue to fill in from the east and pass along the northern skies, contributing to periods of extensive cloud cover for at least the next 2 nights. The bulk of these clouds will shift off toward the NW through Thursday, leaving only residual mid/summit-level clouds in the area for that night; clear skies will likely prevail for Friday and Saturday night.

Precipitable water is expected to exceed 4 mm for the next 3 nights, briefly slip toward 3 mm for Friday night, then increase back to 4 mm for Saturday night.

Increasing mid/low-level turbulence will contribute to poor/bad seeing for the next 3 nights. This turbulence is slated to subside on Friday, just as deep subsidence and relatively calm flow aloft fills into the area, which could allow for good/excellent seeing for Friday and Saturday night.

Little change since the morning forecast...Guillermo is still scheduled to move in from the east and pass roughly 150-200 km and parallel to the northern coasts of the state over the next 3 days. While the bulk of the tropical force winds are expected to pass far enough to the north to pose little impact on the summit, lots of deep widespread moisture will slide over/near the Big Island, which will help erode the inversion and perhaps saturate the air mass below 20 thousand feet between this afternoon and early Friday morning. This will likely result in periods of extensive fog, high humidity, rain at the summit and broken clouds in the area during this time. Isolated convection may also pop up near the Big Island, mainly through tomorrow afternoon and again around Thursday afternoon. A deep ridge is slated to fill in from the ESE in the wake of Guillermo's departure to the NW on Friday. This will allow strong subsidence to build into the area, which will help rebuild a well-defined inversion near 6 thousand feet and ensure a dry/stable summit-level air mass probably through the weekend. Calm flow at and above the summit, combined with this deep subsidence should also allow seeing to dip toward good/excellent values during these nights.
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 Aug 04 - 8 PM60-804-690 / 603.5NE/5-150.7-1.36-10
Wed Aug 05 - 2 AM80-1004-795 / 903.5NE/0-100.8-1.66-10
2 PM80-1004-895 / 905W/5-15NaN6-10
8 PM70-904-795 / 603.5WNW/5-151-24-8
Thu Aug 06 - 2 AM60-804-690 / 503.5SW/5-150.8-1.64-8
2 PM60-804-675 / 406S/5-15NaN4-8
8 PM20-404-575 / 253SE/5-150.7-1.34-8
Fri Aug 07 - 2 AM10-304-560 / 153SE/10-200.5-1.14-8
2 PM0-20Clear5 / 09ESE/5-15NaN2-4
Sat Aug 08 - 2 AM0-5Clear0 / 04.5ESE/5-150.35-0.552-4
2 PM0-20Clear0 / 09.5ESE/5-15NaN3-5
Sun Aug 09 - 2 AM0-5Clear0 / 03.5ENE/5-150.35-0.553-5
2 PM0-20Clear0 / 09ENE/5-15NaN3-5
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 Aug 04 - Wed Aug 05 19:06 20:16 4:40 5:50 22:26 N/A 68 1 23.1 6 18
Wed Aug 05 - Thu Aug 06 19:06 20:15 4:41 5:50 23:13 N/A 57 2 18.4 10 14
Thu Aug 06 - Fri Aug 07 19:05 20:15 4:41 5:50 0:00 N/A 46 3 13.5 13 28
Fri Aug 07 - Sat Aug 08 19:05 20:14 4:42 5:51 0:49 N/A 35 4 08.6 15 51
Sat Aug 08 - Sun Aug 09 19:04 20:13 4:42 5:51 1:40 N/A 25 5 03.5 17 18
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Wednesday 5 August 2015.
Additional Information
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