Latest Forecast for Mauna Kea Observatories
830 AM HST (1830 UTC) Thursday 30 July 2020
Warnings
None
Cloud Cover and Precipitation Forecast
The summit will remain clear, dry and stable through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 11 C this afternoon and 6 C for the night. Winds will be from the east at 5-15 mph, switching to a more NE direction through the night. Seeing will be near 0.35-0.4 arcseconds, while precipitable water is expected to be in the 0.55-0.7 mm for the night.
|
Graphical Summary
|
Discussion
A distinct inversion will continue to cap low-level moisture near 8 thousand feet and ensure a dry/stable summit-level air mass through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.
Skies overhead will remain predominately clear or organized clouds throughout the forecast period, though there is a chance for isolated patches of high clouds moving in from the south on Saturday and Sunday night.
Precipitable water is expected to linger 0.6-0.7 mm for tonight and early tomorrow evening, but will trend toward 1 mm by the end of the latter night and probably 2 mm for early Saturday night. It will likely subside thereafter and settle in below 1 mm again for Sunday and Monday night.
A very stable air mass, combined with calm skies and relatively deep/light easterly flow at and above the summit should allow seeing to settle in near 0.4-0.45 arcseconds throughout most of the forecast period. There is a chance that seeing will dip below 0.4 arcseconds mainly for tonight and again on Sunday night.
A fairly deep ridge will continue to sit to the NNW of the state and promote steady/strong large-scale subsidence in the area and likely prohibit the tropical upper-tropospheric trough from rebuilding in the area until late next week. Nevertheless, the subsidence will easily maintain a very distinct tradewind inversion near 7-8 thousand feet and ensure a dry/stable summit-level air mass throughout the forecast period. This stability, combined with the absence of the TUTT and its southern counterpart, aka the sub-tropical part, will allow calm predominately clear skies to prevail overhead, which should translate to good/excellent seeing over the next 5 nights. Precipitable water will also benefit from the enhanced subsidence associated with the deep ridge and linger at or below 0.8 mm through tomorrow evening. There is a chance that a patch of mid/upper-level moisture passing to the south will briefly increase PW toward 2 mm for Saturday night, but PW is expected to quickly settle back in below 1 mm as this patch slips westward for the following 2 nights.
|