Current Conditions
Temp2.2 C
RH26 %
WindNW 51 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Thursday 28 May (0300 UTC Friday 29 May) 2015
Warning(s)
Chance for fog/high humidity
Moderate winds
Cloud Cover and Fog/Precipitation Forecast
There is a slight risk for periods of fog and high humidity throughout the night; precipitation is unlikely and skies will remain clear.
Summary of Key Meteorological Variables
Summit temperatures will be near 1 C this evening and 0.5 C tomorrow morning. Winds will be from the WSW at 25-40 mph, with seeing around 0.85-0.9 arcseconds. Precipitable water is expected to exceed 4 mm through the night.
Discussion
The tradewind inversion will remain rather indistinct near 10-11 thousand feet for another 12-15 hours, briefly strengthen near 7-8 thousand feet for tomorrow night, then weaken and lift back toward 12-13 thousand feet as the weekend progresses and into the early part of next week. As a result, with the possible exception of Friday night, there is a risk for periods of fog and high humidity at the summit throughout most of the forecast period; precipitation is unlikely. Extensive afternoon clouds are also possible over the next 5 days.

Skies will remain predominately clear of organized high clouds throughout the forecast period, though there is a possibility for summit-level clouds along the northern skies mainly for Sunday and Monday night.

Precipitable water is expected to linger near or exceed 4 mm through the next 5 nights.

Boundary layer turbulence will likely contribute to poor seeing for the next 2 nights. While summit-level winds and thus the boundary layer turbulence are slated to taper early Saturday morning, building light/moderate mid-level turbulence will limit any major improvment in seeing for the remainder of the forecast period.

Minimal change since the morning forecast...The mid-level ridge will remain rather indistinct and/or displaced off toward the west as a low and especially its parent trough lingers to the NNE of the state well into next week. While the bulk of the instability associated with the trough/low will remain off toward the north of the Big Island, mid/low-level moisture will continue to file out of the tropics and over the area, contributing to high PW throughout the forecast period and likely a weak inversion for tonight. Fortunately, low-level forcing/winds below the summit will remain rather weak, which should help limit the risk for fog at the summit for tongiht. In addition, there is a fairly good chance that the inversion will briefly strengthen as the low subtly shifts northward and a weak ridge tries for fill in from the southwest for much of tomorrow. However, the patch of low-level clouds just north of the Big Island is set to sag back southward as the low slips eastward over the weekend. This could lift the inversion toward 11-12 thousand feet and significantly increase the risk for fog and high humidity at the summit particularly for Sunday and Monday night. Finally, summit-level winds will likely linger near 25-30 mph while the low remains intact for the next 2 nights, but is expected to taper once the low slips eastward 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)
Thu May 28 - 8 PM0-10Clear30 / 51WSW/25-400.7-1.14-6
Fri May 29 - 2 AM0-10Clear20 / 50.5WSW/25-400.7-14-6
2 PM20-404-4.525 / 55.5WSW/20-35NaN4-6
8 PM0-10Clear5 / 01.5W/20-350.65-0.953.5-4.5
Sat May 30 - 2 AM0-10Clear5 / 01W/15-300.65-0.854-6
2 PM40-604-4.550 / 106W/10-20NaN4-8
8 PM0-10Clear40 / 51WSW/10-200.55-0.754-6
Sun May 31 - 2 AM0-10Clear50 / 101WSW/10-200.5-0.74-6
2 PM60-804-575 / 256WSW/10-20NaN4-8
Mon Jun 01 - 2 AM0-20Clear60 / 152W/10-200.5-0.84-6
2 PM60-804-575 / 256WNW/10-20NaN4-8
Tue Jun 02 - 2 AM0-20Clear60 / 152WNW/10-200.5-0.84-6
2 PM60-804-575 / 256WNW/5-15NaN4-8
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
Thu May 28 - Fri May 29 19:06 20:18 4:20 5:33 N/A 3:08 82 13 05.5 -6 40
Fri May 29 - Sat May 30 19:06 20:19 4:20 5:33 N/A 3:47 89 13 53.3 -10 12
Sat May 30 - Sun May 31 19:06 20:19 4:20 5:33 N/A 4:30 94 14 43.0 -13 23
Sun May 31 - Mon Jun 01 19:07 20:20 4:20 5:33 17:19 5:15 98 15 35.1 -16 01
Mon Jun 01 - Tue Jun 02 19:07 20:20 4:19 5:32 18:13 6:04 100 16 29.5 -17 56
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 29 May 2015.
Additional Information
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