Maunakea Weather Center

Maunakea Observatories Forecast
5 PM HST Thursday 16 May (0300 UTC Friday 17 May) 2024
Warning(s)
Fog, ice and high humidity
Chance for flurries/rain
Moderate winds
Cloud Cover and Fog/Precipitation Forecast
There is a moderate/high risk for fog, ice and high humidity throughout the night; there is also a small chance for light flurries/rain. Patches of lingering mid/low-level clouds are expected to push off toward the NE for this evening, while deeper more widespread clouds build in from the SW toward the end of the night.

Summary of Key Meteorological Variables
Summit temperatures will be near -0.5 C this evening and -1 C tomorrow morning. Winds will be from the WSW at 20-35 mph, while seeing and PW are expected to linger near or exceed 1 arcsecond and 4 mm, respectively, through the night.

Discussion
Persistent instability will keep the inversion rather indistinct and allow the atmosphere below 15 thousand feet to remain fairly saturated for much of tonight. While there is a chance that the inversion will reform near 7-8 thousand feet late tomorrow, steady of supply of deep mid/upper-level moisture (upward of 12 thousand feet) is expected to drift overhead between sunrise tomorrow and through Sunday night, then disperse in the area on Monday and into Tuesday. As a result, there is a moderate/high risk for fog, ice, high humidity and light flurries/rain through the next 5 nights. Extensive daytime clouds are expected through Monday, but could taper for Tuesday.

Patches of lingering mid/low-level clouds are expected to push off toward the NE for this evening, while deeper more widespread clouds build in from the SW toward the end of the night. A continous supply of thick broken/overcast clouds from the SW are expected to blanket summit skies through much of the weekend. Deep convection may also continue to develop along the western and NW skies over the weekend. The convection will shift further off toward the north late in the weekend, while the bulk of the widespread clouds begin to disperse on Monday, opening up skies for that night.

Precipitable water is expected to exceed 4 mm throughout the forecast period.

A mixture of boundary layer turbulence, instability and/or moisture will contribute to poor/bad seeing through at least Monday evening. There is a chance for a modest improvement in seeing as the atmosphere begins to dry early Tuesday morning.

No change since the morning forecast...The late-season low to the NNW will remain quasi-stationary/steady before weakening and lifting off toward the NE late in the weekend. While the bulk of the instability associated with the low will remain embedded within its associated convergence band over the central portion of the state, the lower-half the atmosphere near the Big Island will remain fairly saturated with an indistinct inversion for tonight. While there is a chance that the lower half of the atmosphere will stabilize a bit and an inversion will reform near 7-8 thousand feet as this convergence band shifts subtly to the west later tomorrow, the low is expected to draw deep widespread moisture/clouds out of the tropics overnight. This moisture/clouds will likely extend above 12 thousand feet (near the Big Island) and will continue to flow over the area, blanketing summit skies mid-morning tomorrow and Sunday afternoon. Convection may develop within the convergence band to the NW, but should pose little threat to the summit during that time. The convection will become less organized and disband off toward the NE as the low breaks down late in the weekend. The low will also lose access to the tropical moisture around this time, but there is a chance that the mid/upper portion of the convergence band will drift eastward, then will disperse in the area early next week. As a result, there is a good chance that fog, ice and/or high humidity will continue to be an issue at the summit probably throughout the forecast period. There is also a possibility for periods of light flurries/rain at the summit mainly through the weekend. Drier more stable conditions should return to the summit once the remaining moisture detrains into the surrounding air mass and the inversion becomes better established by Tuesday afternoon.
5 Day Forecast Summary (Graphical Trend)
HST Cloud Fog/Precip Temp Wind Seeing PW
Cover (%) Height (km) Probability (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Thu May 16 - 8 PM20-404-575 / 25-0.5WSW/20-350.8-1.64-8
Fri May 17 - 2 AM10-304-565 / 20-1WSW/20-350.7-1.53.5-4.5
2 PM80-1004-895 / 653WSW/10-20NaN8-12
8 PM60-804-995 / 750W/5-150.7-1.38-12
Sat May 18 - 2 AM80-1004.5-1090 / 60-0.5W/5-150.7-1.38-12
2 PM80-1004-1090 / 603SSE/0-10NaN8-12
8 PM80-1006-1085 / 500.5ESE/5-150.7-1.18-12
Sun May 19 - 2 AM80-1005-1090 / 600SE/10-200.7-1.18-12
2 PM80-1004-1095 / 653SW/15-30NaN8-12
Mon May 20 - 2 AM70-906-1090 / 60-1NW/5-300.7-1.38-12
2 PM60-805-890 / 405N/10-20NaN6-10
Tue May 21 - 2 AM20-406-860 / 201.5NE/5-150.5-14-8
2 PM20-406-725 / 56ESE/5-15NaN4-6
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 16 - Fri May 17 19:01 20:12 4:25 5:36 N/A 2:21 67 11 16.6 6 39
Fri May 17 - Sat May 18 19:01 20:12 4:24 5:35 N/A 2:51 76 11 58.8 1 01
Sat May 18 - Sun May 19 19:02 20:13 4:24 5:35 N/A 3:22 84 12 41.1 -4 42
Sun May 19 - Mon May 20 19:02 20:14 4:23 5:35 N/A 3:54 90 13 24.6 -10 21
Mon May 20 - Tue May 21 19:03 20:14 4:23 5:34 N/A 4:28 95 14 10.2 -15 43
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 17 May 2024.
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