Latest Forecast for Mauna Kea Observatories
5 PM HST Thursday 08 November (0300 UTC Friday 9 November) 2018
Chance for fog
Possibility for afternoon convection
Cloud Cover and Precipitation Forecast
There is a moderate risk for fog and high humidity throughout the night; precipitation is unlikely. Patches of mid-level clouds may also pass along the SE and eastern skies through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1.5 C this evening and 0.5 C tomorrow morning. Winds will be from the SSW at 15-30 mph, with seeing near 0.8 arcseconds. Precipitable water is expected to linger near or exceed 4 mm for the night.
While there is a possibility that the tradewind inversion will strengthen through the night, mid/low-level moisture passing through/near the area may contribute to periods of fog and high humidity through the night. There is a very good chance that the inversion will breakdown again through Friday night, allowing the atmosphere to turn quite saturated for Saturday night. This will raise the stakes on extensive fog, ice, high humidity and light flurries at the summit durign those nights, particularly the latter. The inversion is set to rapidly recover through Sunday, becoming well-defined near 6 thousand feet and ensure a dry/stable summit-level air mass for that night as well as Monday night. Some afternoon clouds are likely through tomorrow, then will turn extensive for Saturday, only to become minimal and short-lived for the following 2 days.
There is a possibility that patches of mid-level clouds passing along the SE and eastern skies will be visible from the summit through the night. These clouds may creep closer to the Big Island, as thicker clouds build over and drift in from the NW, which will likely contribute to extensive cloud cover for Friday night and mostly overcast skies for Saturday night. All of these clouds are set to shift off toward the east near sunrise Sunday, but may still continue to scrape the SE coast of the Big Island before shifting further eastward early Monday morning, leaving predominately clear skies for that night.
Precipitable water is expected to linger near or exceed 4 mm for the next 3 nights, then plummet toward 0.7-0.8 mm for Sunday and probably Monday night.
A mixture of boundary layer turbulence, mid-level turbulence, an elevated/weak inversion and/or a saturated air mass will contribute to poor/bad seeing for at least the next 3 nights. The air mass is expected to dry out and stabilize on Sunday, but lingering boundary layer/low-level turbulence may still limit much improvement in seeing for that night. Calmer skies should allow seeing to settle in near 0.5-0.6 arcseconds for Monday night.
No change since the morning forecast...The developing low to the NNW of the state will continue to drag mid-level moisture in from the south, which will likely scrape the eastern half of the Big Island over the next 12-18 hours. This moisture could contribute to periods of fog and high humidity at the summit for tonight. There is a slight chance that the inversion will strengthen a bit as a dry sector moves through the area around late tomorrow morning. However, the aforementioned low will begin to send a cold front through the state later that afternoon. The front is not set to arrive at the Big Island until Saturday afternoon, but more mid-level moisture drawn in from the south combined with building instability will likely erode the inversion and increase the risk for fog/high humidity and light flurries at the summit for Friday night. This risk, as well as the possibility for banding convection and brief periods of moderate snow, will increase as the front passes through the Big Island Saturday night. Fortunately, the front is expected to quickly shift off toward the east, allowing very dry/stable air to move into the area by early Sunday afternoon. A ridge following the departing trough and its front will instill strong/steady large-scale subsidence, which will help rebuild the inversion and ensure dry/stable summit conditions for Sunday and Monday night. Precipitable water will respond to this and plummet toward 0.7-0.8 mm, but passing low-level turbulence in the wake of the front may still contribute to poor seeing for Sunday night; seeing should settle toward 0.5-0.6 arcseconds as this turbulence passes for Monday night.