Friday, August 10, 2018

#2083 "Moisture Conveyors"

On April 3rd 2017 the ice was still filling the western basin of Singleton Lake. That ice would not leave the lake until April 10th even though the eastern basin had been ice free since February 25th. It was a very similar day to Friday April 27th, 2018 when I painted the sky. Cirrostratus was coming at us from the west heralding another spring disturbance. The clouds tell the story.

The definition of the noun conveyor is: a person or thing that transports or communicates something. You can think of an atmospheric conveyor belt as a transporter of moisture or maybe a salesperson for clouds. The warm conveyor was spreading increasing amounts of moisture across Singleton Lake. High level cirrocumulus were being replaced by cirrus aligned in gravity waves perpendicular to the winds in the upper atmosphere. Further to the northwest the clouds thickened and the cloud bases gradually lowered. There was nimbostratus far to the northwest. I was out paddling to inspect the remaining ice in the west basin of Singleton Lake but there was lots of time to get that done before the precipitation arrived.

A closer look at the meteorology of the situation reveals that the rotation painted into the cirrus was a vorticity minimum. This means that the col of the associated deformation zone was further to the north which in turn implied that Singleton Lake would not get anything but virga for quite a while. When precipitation did finally arrive it would be in the form of rain. This is what happened and it was all foretold in the clouds.

The graphics below that I constructed for COMET explains how the sense of rotation of the cloud patterns can reveal exactly what portion of the conveyor belt conceptual model is poised to cross your forecast region. The warm front is katabatic downstream from the col in the deformation zone. This means that the warm air is descending above the frontal surface and precipitation must therefore be minimal.

I have painted this scene many times but every day is different. The weather and lighting is certainly unique for each day.

I used a lot of paint on this very rough panel. It was fun.
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