Current Conditions
Temp5.1 C
RH15 %
WindE 0 mph
Mauna Kea Observatories Forecast
5 PM HST Monday 06 July (0300 UTC Tuesday 7 July) 2015
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for fog and high humidity toward the end of the night; skies will remain clear and precipitation is not expected.
Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C this evening and 3 C tomorrow morning. Winds will be from the NE at 5-15 mph, with seeing near 0.45-0.5 arcseconds. Precipitable water is expected to be in the 2.5-3.5 mm range for the night.
The tradewind inversion will continue to cap low-level moisture near 7-8 thousand feet through at least this evening, but is expected to erode as a couple of patches of deep tropical moisture begins to fill into the area probably through the remainder of the week. This may allow the atmosphere to periodically become saturated below 20-25 thousand feet over the following 4 nights. Consequently, the risk for fog, high humidity and eventually precipitation through tomorrow and is virtually expected mainly between midnight Wednesday and early Friday morning. Isolated convection is also possible particularly for Thursday. Extensive daytime clouds are likely for the remainder of the week.

Skies will remain predominately clear for tonight, but there is a possibility for summit and/or low-level clouds for tomorrow night, and thicker clouds may pass through or even develop in the area for Wednesday and Thursday night. The bulk of the clouds are slated to shift further westward and along the northern skies on Friday, leaving only residual pockets of clouds over/near the summit for that night.

Precipitable water is expected to linger near 3 mm for tonight, and will likely exceed 4 mm for the remainder of the forecast period.

Minimal turbulence in the atmosphere will allow for better than average seeing for tonight. However, an influx of mid/low-level turbulence will likely degrade seeing over the following 2 nights, and likely contribute to bad seeing for the second half of the forecast period.

Little change since the morning forecast...Although the mid/low-level ridge will continue to sit to the north of the state probably through the week, remnant moisture from a tropical wave is scheduled to move in with the low-level flow during the second half of the night. This moisture is slated to weaken/lift the inversion through tomorrow, perhaps leading to a fairly saturated air mass below 18 thousand feet for much of that night. There is a possibility that the inversion will try to strengthen and/or the air mass will briefly dry out as the bulk of the moisture starts to get swallowed up by a developing tropical storm on Wednesday. While there is still large uncertainties associated with this storm (both track and intensity), current model run expects it to form near 135 W, 12 N over the next 12-24 hours, then track toward the Big Island and strengthen (to a boardline Cat 1 Hurricane, if that - I suspect that's generous) over the next few days. Upon reaching 150 W, 20 N around Thursday night, it is then slated to slowly weaken as it begins to encounter shear associated with an upper-level low to the northwest and then pass parallel ~100-200 km to the north of the state over the weekend. Unfortunately, moisture along the storm's easterly fringe is expected to reach the Big Island area late Wednesday evening and saturate the air mass for Thursday and into Friday. This will likely result in extensive fog and rain at the summit, and perhaps isolated convection in the area during that time. While the bulk of the instability is slated to shift off toward the north with the storm, poor conditions/skies may persist due to lingering/residual moisture over the weekend.
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 06 - 8 PM0-5Clear0 / 03.5NE/0-100.4-0.52.5-3.5
Tue Jul 07 - 2 AM0-10Clear20 / 03NE/0-100.4-0.62.5-3.5
2 PM60-804-560 / 156.5ESE/0-10NaN4-8
8 PM10-304-575 / 252.5SE/5-150.5-0.84-6
Wed Jul 08 - 2 AM10-304-575 / 252S/5-150.5-0.94-6
2 PM80-1004-890 / 306SSW/5-15NaN4-8
8 PM70-904-880 / 202.5WNW/0-100.5-14-8
Thu Jul 09 - 2 AM80-1004-995 / 601.5S/0-100.8-1.66-10
2 PM80-1004-1095 / 904.5ESE/5-15NaN10-15
Fri Jul 10 - 2 AM80-1004-995 / 901.5ENE/5-151-28-12
2 PM80-1004-690 / 507SSW/10-20NaN8-12
Sat Jul 11 - 2 AM20-405-675 / 254S/10-200.6-1.48-12
2 PM60-804-690 / 507ENE/10-20NaN8-12
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 06 - Tue Jul 07 19:15 20:28 4:25 5:39 22:57 N/A 66 23 48.1 -1 13
Tue Jul 07 - Wed Jul 08 19:15 20:28 4:26 5:39 23:42 N/A 54 0 42.2 3 15
Wed Jul 08 - Thu Jul 09 19:15 20:28 4:26 5:39 0:28 N/A 43 1 36.2 7 28
Thu Jul 09 - Fri Jul 10 19:15 20:28 4:27 5:40 1:14 N/A 32 2 30.4 11 10
Fri Jul 10 - Sat Jul 11 19:15 20:28 4:27 5:40 2:02 N/A 22 3 25.0 14 11
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 7 July 2015.
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