Figure 9.
The low-pressure
system to the north of
the Hawaiian Islands,
on February 10, 2019,
Hawaiian Standard
Time. The circulation
center is clearly visible
in the lower-level cloud
pattern (in grey). Image
taken from the MKWC
satellite archive ; go there
and select 11-Feb UTC to
see animations.
cal of the widely-reported peak
gust speed of 191 miles per
hour (mph), winds in excess of
150 mph (just below Category
5 Hurricane force) were reliably
recorded on the summit on that
day (Figure 10). icant failures would be expected. The recent
additions to the support building, namely
the many solar panels and base-facility op-
eration environmental sensors, were de-
signed to the same wind speed standard as
the rest of the building, and all survived the
wind event intact and remained functional.
Winds of that speed at this el-
evation, pushing on a structure
of the scale of the Gemini dome,
is sufficient to produce a force of
around 280 tons sideways. The
Gemini telescope facility is rated to survive
such winds with no distress to materials or
structure. Even somewhat stronger winds of
order 160 mph would not threaten the struc-
ture, as deformations would remain below
the elastic limit. However, at 200 mph, signif- This wasn't a particularly unusual storm sys-
tem; it was a “Kona low," a low-pressure sys-
tem which usually settles to the west of the
islands (hence the name) but which this time
was to the north. To put the wind speeds in
perspective, an extreme winter storm on
Mount Washington in New Hampshire, USA,
in 1934, produced a wind gust of 231 mph,
and in 1996 Cyclone Olivia produced a wind
gust of 253 mph, setting a new world record.
Figure 10.
Top panel: The CFHT/
Gemini observed
weather data from the
Maunakea Weather
Center site , at the
time (16:43 HST) of the
highest gust experienced
there — 161 mph
(top row, middle, red).
Bottom panel: This
screenshot from the
Maunakea Weather
Center shows a wind
speed of 96 knots (110
mph) recorded by the
CFHT/Gemini weather
tower on February 10th
at 16:40 HST (bottom
frame).
68
GeminiFocus
January 2020 / 2019 Year in Review