Latest Forecast for Mauna Kea Observatories
5 PM HST Friday 13 October (0300 UTC Saturday 14 October) 2017
Warnings
Fog, high humidity and ice
Chance for convection and snow/rain
Cloud Cover and Precipitation Forecast
Fog, high humidity, clouds and ice will continue to plague the summit through the night. There is a good chance for convection in the area and periods light snow/rain over the next 12-18 hours.
Summary of Key Meteorological Variables
Summit temperatures will be near 0.5 C this evening and -0.5 C tomorrow morning. Winds will be light and from the south, while seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm, respectively.
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Graphical Summary
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Discussion
The atmosphere near the Big Island will remain saturated and unstable, likely allowing extensive fog, high humidity and periods of ice to plague the summit through Sunday evening. There is also a chance for convection in the area and light rain/snow at the summit mainly over the next 36 hours and perhaps again on Sunday afternoon. The inversion is set to quickly recover near 7-8 thousand feet through Monday, ensuring the summit remains dry and stable for that night as well as Tuesday night. Extensive daytime clouds and perhaps even afternoon convection are expected through Sunday, then will become minimal and short-lived for the early part of next week.
Thick clouds surrounding the Big Island will contribute to extensive cloud cover or even periods of overcast skies for the next 2 nights. These clouds will shift off toward the west, opening up skies through Sunday night. However, there is a chance that scattered high clouds passing along the southern skies will move northward and scrape the western tip of the Big Island for the early part of next week.
Precipitable water is expected to exceed 4 mm through Sunday night, then will plummet toward and settle in near 1 mm for Monday and Tuesday night.
Instability, turbuence and moisture will contribute to inoperable conditions and likely poor/bad seeing through at least Sunday evening. There is a chance for a moderate improvement in seeing through Monday, but persistent shear/turbulence in the free atmosphere will likely keep seeing near 0.6-0.7 arcseconds for the early part of next week.
No change since the morning forecast...A strengthening mid/upper-level trough to the north will continue to destabilize the air mass for the next 36-48 hours, then will shift off toward the SE as a rather deep ridge fills in from the west late in the weekend and for the early part of next week. Unfortunately, widespread moisture filling in from the NE via the low-level trades will take advantage of this instability, contributing to mostly inoperable (foggy, high humidity and ice) summit conditions through at least Sunday evening. Although the blob of convetion to the east will likely dissipate a bit over the next 6 hours, there is a good chance that these clouds will move in over the summit and flare up again late this afternoon/evening. This could bring extensive cloud cover, convection to the area (particularly along the eastern slopes) and a mixture of light snow/rain at the summit for tonight. More patches of (mostly less organized) moisture will continue to flare up and drift in from the NE as long as the mid/upper-level trough persists to the north. This cloud allow for more rounds of mostly afternoon/evening convection and snow/rain at the summit into Sunday afternoon. The return of the aforementioned ridge to the north will help bring subsidence to the area and rapidly rebuild a well-defined inversion neare 8-9 thousand feet on Monday, ensuring dry/stable conditions at the summit for the early part of next week. However, there is a good chance that subt-tropical jet entrance region will linger overhead, shuttling high clouds through the area and allowing moderate turbulence to prevail in the free atmosphere during that time.
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