From the Cliff High Volume Weather Blog
Cliff Mass
A tragedy struck yesterday (Sunday, September 4) with a plane crash floating over Mutiny Bay south of Whidbey Island just after 3pm (see map below, star indicates where it happened) accident).
The plane was en route from Friday Harbor to Renton. Like all plane crashes, it will be thoroughly examined by the National Transportation Safety Board (NTSB), which is very valuable. Air travel is extremely safe as the causes of past crashes are carefully investigated and the system is improved as a result.
Several people have asked me if there is a meteorological factor contributing to this terrible occurrence, and after examining the data, I found something significant.
Let me show you right now.
During the exact time of the crash, a front was moving through the area and this passage, interacting with the local terrain, created very strong low-level wind displacement during the Olympics. .
Below are surface observations at 3pm. To the south of the accident site, the wind is from the south (the prongs face the direction the wind is coming from) while to the north the wind is from the northwest.
The temperature in the south stream is much warmer than in the north stream.
Such low-level convergence of airflow is often accompanied by a frontal wind over Puget Sound and often produces a band of clouds and precipitation: the infamous Puget Sound Convergence Zone.
This transition can be very sharp, as a cold northerly air mass crosses and pushes a warmer current southward (see diagram longitudinal section below).
To see how sharp the transition is, let me show you observations from a surface observation site (Bush Point), just north of Mutiny Bay (WeatherUnderground history).
The bottom panel is the wind direction. Well… a VERY strong, almost instantaneous wind shifted from South to North at 3pm. The top panel (red line) shows the temperature, which drops sharply behind the windshield. Other nearby observations suggest the same thing.
The 3pm visible satellite image shows a band of clouds associated with the windshield diameter.
Not very impressive really, and the weather radar doesn’t show how much rain works with the windshield diameter (see below).
3pm weather radar
The vertical structure of the leading edge of the wind shift (illustrated in the figure above) will be a narrow wedge of the low-level north wind, with the southerly wind directly above it. High resolution UW WRF model simulations show such a structure (see simulated sound with pitch at 2pm for the point in question). Camano Island’s radar also recorded the same thing.
With all this in mind for meteorology, let’s return to the floating plane crash. According to Flightradar24 (below), the aircraft was flying about 600 ft AGL, climbed about 1000 ft, and then rapidly lost altitude at 3:09 pm (2209 UTC). The previous aircraft speed was around 125 knots and then lost speed shortly after 3:08 pm.
Not only can the wind change direction suddenly, but there can also be significant turbulence due to the strong vertical shear associated with the convergence line/wind axis.
Does this have anything to do with this crash?
I do not know. All I can say is that the crash occurred in an area with active wind shifts and low potential for turbulence. Was it a coincidence that the crash coincided with their passing through the high winds?
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