Current Conditions
Temp8.3 C
RH15 %
WindNNE 9 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Friday 23 September (0300 UTC Saturday 24 September) 2022
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while broken high clouds continue to fill out of the SW and contribute to extensive cloud cover for the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 8 C this afternoon, 3 C this evening and 2.5 C tomorrow morning. Winds will be light and from the north, with seeing near 0.5-0.55 arcseconds. Precipitable water is expected to be in the 3-4 mm range for the night.
Discussion
A fairly well-defined 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 through tomorrow, but could pick up a bit for Sunday, only to become minimal and short-lived again for the early part of next week.

A band of broken high clouds will continue to fill out of the SW and contribute to extensive cloud cover for tonight. This band will sag southward through tomorrow, leaving predominately clear skies for that night. There is a possibility for patches of mid/upper-level clouds passing along the western skies for Sunday night; clear skies will prevail again for the following 2 nights.

Precipitable water is expected to linger in the 3-4 mm range through the weekend, but clouds trend toward 2 mm through Monday night and probably 1 mm through Tuesday night.

While there is a possibility for moderate free atmospheric turbulence associated with vertical shearing over the next 2 nights, as well as some mid-level moisture in the area for Sunday night, seeing should still linger near 0.5-0.6 arcseconds through the weekend. Winds at and above the summit will become quite light and out of the east minimizing free atmospheric turbulence thereafter, but there is a chance for an increase in low-level turbulence which may degrade seeing toward 0.6-0.7 arcseconds for the early part of next week.

No change since the morning forecast...Although the mid-level ridge will remain rather indistinct until the early part of next week, a well-defined surface ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area throughout the forecast period. This subsidence will help maintain a well-defined inversion near 8-9 thousand feet and ensure a dry/stable summit-level air mass through next 5 nights. The upper air pattern will continue to transition from a summer-time flow (with the tropical upper-tropospheric trough) to the strengthening of the westerly jet far to the north and the development of synoptic lows. Initially, the decaying TUTT will send broken high clouds in from the tropics and contribute to extensive cloud cover over the next 12-18 hours. The bulk of these clouds will slide off toward the east at the TUTT decays and shifts eastward in response to a passing short-wave trough far to the north as the weekend progresses. This should leave predominately clear skies over head after tonight, though there is a small chance for patches of mid/upper-level clouds along the western skies for Sunday night. The decay of the TUTT/STJ will help reduce vertical shear in the free atmosphere, but better than average seeing should still prevail as mostly calm skies persists below 20 thousand feet through the weekend. There is a chance for the development of a secondary inversion between 15-18 thousand feet as the mid-level ridge begins to take shape in the area for the early part of next week. This could generate low-level turbulence and perhaps degrade seeing a bit for Monday and Tuesday night.
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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Fri Sep 23 - 8 PM70-908.5-100 / 03N/0-100.5-0.73-4
Sat Sep 24 - 2 AM60-808-100 / 02.5N/0-100.45-0.653-4
2 PM20-408-90 / 08NNW/5-15NaN4-6
8 PM0-20Clear0 / 03NNE/5-150.45-0.653-4
Sun Sep 25 - 2 AM0-20Clear0 / 02.5NNE/5-150.4-0.63-4
2 PM20-404-50 / 09NNE/10-20NaN4-6
8 PM0-206-70 / 04NE/10-200.5-0.73-4
Mon Sep 26 - 2 AM0-206-70 / 03.5NE/10-200.45-0.653-4
2 PM0-20Clear0 / 08ENE/5-15NaN3-5
Tue Sep 27 - 2 AM0-10Clear0 / 03E/5-150.5-0.82-3
2 PM0-20Clear0 / 08ENE/5-15NaN1-2
Wed Sep 28 - 2 AM0-10Clear0 / 02.5E/0-100.5-0.81-1.5
2 PM0-20Clear0 / 08.5NE/5-15NaN2-4
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 Sep 25 - Mon Sep 26 18:24 19:28 4:59 6:03 6:48 18:40 0 12 38.5 -1 20
Mon Sep 26 - Tue Sep 27 18:23 19:27 4:59 6:03 N/A 19:15 2 13 25.2 -7 16
Tue Sep 27 - Wed Sep 28 18:22 19:26 4:59 6:03 N/A 19:52 7 14 13.9 -13 01
Wed Sep 28 - Thu Sep 29 18:21 19:25 4:59 6:03 N/A 20:33 13 15 05.6 -18 16
Thu Sep 29 - Fri Sep 30 18:20 19:25 5:00 6:04 N/A 21:19 22 16 00.9 -22 40
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 26 September 2022.
Additional Information
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