The Dry Conveyor Belt

#2057 "Deformation Cirrus"

This is the next step in understanding the conveyor belt conceptual model (CBCM) which replicates the wind patterns found with a mid latitude low pressure area. The CBCM is fundamental to the understanding of cloud and weather patterns. The idealized conveyor belts are in the atmospheric frame of reference relative to the low.

Dry Conveyor Belt (DCB - Orange Arrow)        

The dry conveyor belt (DCB) is the contrasting dance partner for the warm conveyor belt (WCB) in the weather ballet. The warm conveyor belt transports heat and moisture northward. The dry conveyor belt takes cooler and drier air southward. Both are essential to the energy balance of the earth so that in the long term the distribution of heat and moisture around the globe is in balance.  Both are also tied together by the jet stream which is the purple arrow in the CBCM graphic.  

The dry conveyor belt originates from high levels at more northern latitudes and follows the constant energy isentropic surfaces downward as it plows toward the south on the western flank of the warm conveyor belt (WCB). The air is relatively dry to start with and becomes drier and warmer as it descends. There are minimal cloud tracers and the atmosphere uses invisible ink to write this part of the weather story of the storm. The croquet hoop and smoke ring analogies can still be used but without cloud or smoke, one must use your imagination to visualize the circulation. 

The leading edge of the dry conveyor belt is also a bowed shaped deformation zone. The anticyclonic branch of the dry conveyor belt tends to penetrate further south and lower in the atmosphere. This anticyclonic companion flow is drier, lower and warmer that its cyclonic companion across the guiding flow. The cyclonic companion typically turns east or even northeastward and rises again on the sloped isentropic surfaces. These circulations help to define the character of the cyclonic companion of the warm conveyor belt and the associated cold front.

Water Vapour Imaged June 1st, 2020
http://weather.rap.ucar.edu/http://weather.rap.ucar.edu/

How does one study something that is dry? The dry conveyor belt is largely invisible on the visible and infrared satellite imagery. Notable by the absence of clouds. This is not the case in water vapour (WV) imagery which senses the top few millimeters of water vapour uppermost in the atmosphere. Now you know why I embraced the lower resolution and grainy water vapour pictures when they first appeared in the forecast office. The patterns and shapes so obvious in the clouds and weather of the warm conveyor belt were also present in the dryness of the DCB. The dry air also moved like a fluid choreographed by the other another important air flow. In forecast operations this required even more arm waving... more than most meteorologists could take.

Water Vapour Imaged June 1st, 2020 - Detail of the DCB

I use the water vapour imagery to summarize the dance moves of both the warm and dry conveyors belts. In the process of summarizing the weather story behind a painting, it is the only piece of data I ever really need to archive. 

Here is the water vapour image that tells the tale behind #2057 "DeformationCirrus". The accompanying graphics will refresh the lessons learned about the warm conveyor belt and the deformation zone conceptual model which is the star of the painting. Next week we will learn even more about the dry conveyor belt (DCB).

Warmest regards and keep your paddle in the water,

Phil the Forecaster