The Relativity of the Companion Flows in the Warm Conveyor Belt

#1713 "December Morn" Pixels Link

Trying to measure the absolute value of anything is a challenge. One would require access to the entire data set which is often simply impossible.  Climate change is one example of this. Forecasting COVID-19 is another…

But everything is relative in nature. In the natural world we can compare and comparatively better understand the nature around us without measuring the entire globe. The warm conveyor belt offers a great opportunity to do just that.

I have been presenting the warm conveyor belt as a single entity. In reality the warm conveyor belt has a split personality and it is vitally important to know both sides. The companion vortices described in the three dimensional smoke rings are shaped by their companion flows. The dividing line is the streamline that follows the centre of the warm conveyor belt flow and points straight at the col. Looking along the direction of the flow, the streamlines to the right of the divide rise and curl anticyclonically as they approach the deformation zone skin.  Streamlines to the left of the divide rise and swirl cyclonically as they near the deformation zone. These swirls connect as described before in the “Unified Theory of Swirls”. But it really helps to look at them in a bit more detail to better understand the weather.

When in forecast operations, I used my hands to better visualize air flows and the conceptual models that applied to a given weather concern of the day. I used my right hand a lot and did a considerable amount of arm waving in trying to better explain the processes. That was before PowerPoint and the fantastic graphic artists and animators of COMET.  In those early days meteorology was kind of like break-dancing without anything getting broken. I had wished that more of my fellow meteorologists had joined in the dance but I probably didn’t explain the science well enough. The workload was heavy and there were simpler ways to produce a forecast. Meteorologists were drowning in data anyway with the burgeoning numerical modelling and statistical approaches to weather prediction. My approach was to simplify the atmosphere by putting the data into the context of conceptual models and satellite imagery.  But I digress… let’s look at the anticyclonic companion in the warm conveyor belt.

If one follows the atmospheric frame of reference wind direction from the ground up to the right of the col, your arm initially points from the northeast in the cold conveyor belt. Winds are named by the direction they blow from. When you mentally reach the level of the elevated warm front, your arm will point more from the southeast. As you continue to climb in your mind, your arm will turn more to the south and then to the west or northwest as it reaches the level of the downstream confluent asymptote of the deformation zone. If you recreate your arm motions with height, your arm turns clockwise or veers with height. Winds veering with height is equivalent to the relative warming of the atmosphere with height. This leads to stabilization of the vertical profile. The proverbial hot air balloon will encounter warm air at higher heights and stop rising. This profile has large impacts on the weather and the shapes of the clouds. The typical clouds found in in the stable atmosphere of the anticyclonic companion branch are named and located in the accompanying graphic.

Gravity waves are common in the anticyclonic companion. Gravity waves require a stable layer to develop. These cloud waves are everywhere perpendicular to the winds in the atmosphere. Like waves on a lake, the size and distance between the cloud crests increase with the wind speed. The size and the spacing of the three white bars in the graphic are intended to represent the gravity waves superimposed on the described cloud types. Gravity waves are also your best friends when you want to witness the relative wind directions in the atmosphere.


A picture can save a lot of words and I have included a few graphics to better explain what to look for in the anticyclonic companion branch of the warm conveyor belt.

The other way to try to discern the atmospheric wind is to simply line up a cloud element with something that is not moving and watch it move. The problem with this approach is that the average motion of the atmosphere is added to the winds measured relative to the atmosphere itself. Your single view does not contain all of the data required to calculate the average wind that is translating your clouds. The earth frame observed wind can be ambiguous and difficult to understand in terms of a simple conceptual model like the Conveyor Belt Conceptual Model as pictured. As a start though one can assume that storm motion has a component both from the south and the west and that average wind is blowing the Conveyor Belt Conceptual Model along. Operationally I used satellite imagery to calculate the average speed of translation over the area of weather that I was concerned about.

I also observed this meteorology while paddling and painting.  Just a few examples that I remember are #1713 "December Morn" as pictured at the start of this post, #1908 "Cirrious Stories" and #1928 "Turtle Rock McCrae". There are many more in my portfolio of 2350 paintings and counting...

There is no final exam on any of this stuff. I present it with the sincere hope that you might enjoy nature as much as I do...

Warmest regards and keep your paddle in the water,
Phil the Forecaster

PS: Much more to come and thank you to my COMET friends in Boulder who helped to publish some of this stuff.

Applying Croquet to the Warm Conveyor Belt

2083 "Moisture Conveyors" Pixels Link

In "The Main Veil of the Weather Dance - The Warm Conveyor Belt" I made the case for the Warm Conveyor Belt as the prima ballerina in the weather ballet and the "Conveyor Belt Conceptual Model".  In "What do Smoke Rings have to do with Croquet?" I described how the leading edge veil of the Warm Conveyor Belt was a stretchy three dimensional deformation zone fabric that contained the flow of the atmospheric river. Using the smoke ring analogy I then showed how the vorticity ring evolved into a croquet hoop on the warm side of the surface warm front. I then alluded to using this croquet hoop as a forecasting tool. This is how I did that.

The precipitation associated with a storm is the result of both the intensity and the duration of the precipitation. These characteristics can be quickly estimated by looking at the croquet hoop representation of the warm conveyor belt. I will use a graphic to try to save a lot of words. 

The moisture in the warm conveyor belt travels northward, rising for free on the constant energy surfaces meteorologists call isentropic surfaces. This view is looking northward along that path through the croquet hoop just south of the surface warm front. 

A brief explanation of the important features of the croquet hoop are included in the graphic. Pressure is the weight of the air above a point. The rising air of the cyclonic swirl of the croquet hoop causes pressure falls. Precipitation processes releases energy that fuels the rapid rise of air in this cyclonic croquet leg. Meanwhile the sinking air along the anticyclonic peg results in rising pressure. The pressure difference between these two legs determines the wind speed of the conveyor belt delivering heat and moisture energy to the storm. This current of energy is often called an atmospheric river and the pressure difference across the river keeps it flowing and determines the current.

The orientation of the warm conveyor belt as revealed by the plane of the croquet hoop is also vitally important. The following graphic might help explain this better but it all has to do with the atmospheric frame of reference and the direction of flow of that atmospheric river.  The importance of the atmospheric frame of reference was made in the very first post in this series "Cloud Shapes and Lines in the Atmosphere". 

The tilt of the cyclonic vorticity tube that is the rising swirl of the croquet hoop will typically be the same as the orientation of the warm conveyor belt.  If this cyclonic vorticity tube tilts to the northwest expect a slow moving or stationary weather system where both duration and intensity of the precipitation will be a concern. 

Now for some fun... A time tested "rule of thumb" at the Ontario Storm Prediction Centre in Toronto is to count the isobars originating from the warmth and moisture of the Gulf of Mexico. If you should count four isobars (drawn at 4 millibar intervals) directed from this huge energy source then you can simply predict significant precipitation in Toronto in 24 hours. A significant atmospheric river requires 16 millibars of pressure difference from bank to bank. 

There was a tendency during my meteorological career to shun these techniques as "cook book meteorology" in favour of numerical modeling of the atmosphere.  My response was that even the best chefs refer to a reference guide especially if these were based on solid science and knowledge. 

My illustrations for this application of the croquet hoop guide to the warm conveyor belt follow. They are computer generated.  I am retired and was looking for a case to illustrate the atmospheric river approach to the warm conveyor belt and croquet hoop. I stopped doing hand drawn analyses long ago even though it was my favourite task and where I really learned about the weather. 

The analysis image on the left showed at least five isobars drawn at 2 millibar intervals (10 to 12 millibars of pressure difference across the atmospheric river) coming off the Gulf of Mexico . The 24 hour forecast chart on the right showed the rain well into Southern Ontario. Indeed, it poured and produced major spring flooding across the province


Why think of these things? Trying to understand how the real world works is way better than the other options. The weather is a beautiful ballet and not a battle.

There is much more to come...

Warmest regards,
Phil the Forecaster Chadwick

PS: The orientation of the warm conveyor belt related to event duration described is intended as a generalization - but one that applies well for central and eastern Canada. There is a well-known and strong and nearly stationary atmospheric river that points northeastward to the west coast.  This "Pineapple Express" imports a lot of moisture and heat energy from the tropical Pacific around Hawaii into the west coast and duration is the problem. 

What do Smoke Rings have to do with Croquet?

1061 "Windy St Lawrence" Pixels Link
There is an explanation for every line in the sky...

Smoke rings grow with time. Entropy is always increasing. But even the atmosphere has a limited vertical extent. What happens when those limits are approached? What does all of this have to do with croquet? This material has never been published. I used it operationally but that is it. There was considerable push back in the early years probably because I did not explain it well enough.

The dominant smoke ring associated with the strongest puff is what we will consider. The smoke is just there to trace the air circulation. Those movements of air occur whether or not we can see them. The deformation zone must be bowed in the direction of the strongest puff. The companion vorticity or swirl centers must straddle this strongest puff. Simple truths. 

Looking down on a quasi-horizontal
isentropic surface cross section
through a puff (large purple arrow) and
smoke ring (large companion X and N swirls)  -
 the deformation zone conceptual model
with col "C" and two outward pointing
green confluent asymptote arrows

The leading surface of the air mass being blown forward is the deformation zone veil or skin. The intersection of this deformation zone veil with the ground is the surface front. But what happens when the smoke ring expands to collide with the ground? The graphic below includes the right hand rule for each of the four legs of a more rectangular smoke ring. In previous descriptions of the smoke ring conceptual model, I had only included the companion swirls that border the puff blowing into the page at the black X. These companion vortices tend to be more meteorologically exciting but I think the top and lower branches also have a story to tell.

Looking along the puff through a vertical 
cross sectional plane perpendicular to that puff (black X in the middle) 
and smoke ring (large companion X to the left 
and N to the right) 

What happens when the smoke ring increases in size and encounters the edges of the free atmosphere. This is how that collision played out in my imagination. The primary circulation is the swirl described by the fingers of your right hand. A derivative flow indicated by the direction of the thumb results from the swirl as a form of cause and effect. 

Frictional mixing of the lowest branch of the smoke ring must occur at the earth. The primary and secondary motions of the swirl described by your right hand are reduced by friction and are certainly disrupted if not stopped all together.

Now follow the smoke ring with your right hand. Friction has eliminated the direct smoke ring flow into the rising current associated with the vorticity maximum swirl. Replacement air must be drawn inward at the base of the vorticity tube. This inward flow certainly increases the low level cyclonic vorticity in the atmospheric frame of reference.

Following the smoke ring further with your right hand, the tropopause branch of the smoke ring would be largely unaffected. The equation of continuity requires that what goes in must also go out. The swirl would produce ascending air in the relative atmosphere which enhances the contrast with the air on the other side of the deformation zone.

Making the turn downward the air following the right thumb would impact with the ground and spread out anticyclonically. The original preferred path found in the free atmosphere would be disrupted by friction and the chaos of the boundary layer that was described briefly previously. 

The branch of the smoke ring swirl has been
eliminated by friction near the earth in
the planetary boundary layer

This decay of the portion of the smoke ring encountering the friction of what meteorologists call the planetary boundary layer, turns the smoke ring into a croquet hoop. The surface front is located just beyond the hoop constructed of a cyclonic vorticity tube to the left and an anticyclonic vorticity tube to the right.

The vorticity maximum spins as a tube anchored on the surface within the dominant air mass. This vortex might actually increase aided by precipitation processes. This vortex must lie to the south of any low pressure centre analyzed on a surface map in the earth frame. Any surface front will be analyzed into the surface low and not the vorticity maximum potentially revealed by a detailed streamline analysis.

Similarly the vorticity minimum tube spins within the dominant air mass. This vorticity minimum must lie to the north of any high pressure centre analyzed on a surface map in the earth frame.

As the translation of the storm slows, the low will shift toward the atmospheric frame croquet vorticity maximum tube. Similarly any surface high will shift toward the croquet vorticity minimum tube.

The atmospheric engine enters an important stage at the smoke ring to croquet transition. The downward exhaust vortex can easily dump its flow on the earth. This flow can fan out almost without limit as the high pressure centre. The upward cyclonic portion of the atmospheric engine is very different. The cyclonic updraft is fueled by the atmospheric energy of heat and moisture released through precipitation processes. The updraft of the cyclonic swirl increases in speed requiring more replacement air to be drawn in at the ground level. Relying on physical experience and not mathematics, the inflow of air must come from larger areas near the surface. The rotation of the earth and the Coriolis force deflects these currents of air to the right. The Coriolis force increases the cyclonic rotation of the updraft vortex of the croquet hoop atmospheric engine. Wow!

Why think about these things? The conceptual models we have created are important because they reflect real life meteorology that happens every day. One can see the patterns and in an instant apply the appropriate conceptual model and understand what the atmosphere is up to. That is weather forecasting. The water vapour imagine below depicts the recent storm. Why the water vapour imagery is my favourite data source is a long story dating back to a terrific and life changing 1982 presentation by Roger Weldon. That journey will be told but not today. For now I can explain each of those lines and details but... one can simply appreciate the atmospheric processes by employing a simple conceptual model that has been developed over the years of observing the weather. The warm conveyor belt of yesterday's storm was surging through the atmospheric croquet hoop (the transparent three dimensional dark hoop) like a fire hose.

Water Vapour Easter Monday April 13th, 2020

I know some talented graphic artists and animators at COMET in Boulder Colorado who could make these concepts sing while extracting the maximum amount of science. Here is an animation of a dust devil which would be similar to what I imagine happens along the cyclonic upright of the croquet hoop.

My wife reminds me that I am retired. It is time to make coffee. Both of these statements are certainly true. But I do believe in the simple wonder of nature that surrounds us all and asking "why". I think we can find simple joy surrounded by the untold wonders of nature. Whether (weather) we fully understand these marvels does not really matter and in no way lessens our pleasure.

Warmest regards,
Phil the Forecaster

PS: Much more still to come...

The Main Veil of the Weather Dance - The Warm Conveyor Belt

2218 "Sunset Concert in AC and CI" Pixels Link

Warm Conveyor Belt - WCB in Red 

The warm conveyor belt (marked WCB in the figure as the red flow) represents the main source of warm, moist air that feeds the cyclone. Heat and moisture are energy for the development of the low pressure area. The warm conveyor belt originates in the warm sector of the cyclone far to the south and flows poleward roughly parallel to and ahead of the cold front – rising as it travels northward for free on the isentropic surfaces.  (See "Isentropic Surfaces - Science and Art Merges") This layer can be 5000 feet deep and typically begins in the convective mixing layer far to the south well away from the low center. As the flow approaches the warm front, it continues to ascend with its strongest rise over and north of the warm front. This is the area of strongest warm air advection.

The leading edge of the warm conveyor belt is the deformation zone (see “A Closer Look at Lines in the Sky”) The flow splits at the col. Looking downstream to the right of the col, the flow turns anticyclonically or clockwise as it joins the jet level flow in the upper troposphere. Placing the fingers of your right hand in the direction of the curl must point your thumb downward. This is the anticyclonic vorticity centre of the deformation zone and it links to a high pressure circulation at the surface.

Looking upstream to the left of the col, the flow starts to turn cyclonically or counter-clockwise as it wraps around the low pressure area and the cyclonic circulation. Placing the fingers of your right hand in the direction of the swirl must point for thumb upward. This is the cyclonic vorticity centre of the deformation zone and see how it links to the low at the surface. This was described in blog “Rotation is the Key to Unlock Cloud Shapes”.

Together the companion anticyclonic and cyclonic swirls link in three dimensions into one large smoke ring in the sky. The was described in the "The Theory of Unified Swirls" using Bob Dylan's smoke ring to explain the circulations in a fluid. Similarly the companion swirl centres associated with each deformation zone that describes a smoke ring, are also three dimensional. These vorticity tubes extend in the vertical reaching right down to the ground near the warm front. The smoke ring morphs into a Croquet hoop at the warm front as well - more on that later.

My view for painting 2218 "Sunset Concert in AC and CI"

In addition the deformation zone is three dimensional! The deformation zone line is just where the deformation zone veil that encloses the warm and moist air mass, intersects with an isentropic energy level. If we take a cross-section along the warm conveyor belt we can see air parcels of different potential energy following the isentropic surfaces on their free ride northward.

The ingestion of air into the engine of the cyclone takes place over days as the system grows in size and energy. Some of these air sources will be more moist than others. In the absence of convective instability, these different air sources will find their assigned energy level in the isentropic conveyor belt and gently rise as they move northward. Layers of moisture will often remain separated from each other.

The warmest potential temperature air is highest in the atmosphere. The leading edge of this moisture creates the highest deformation zone and leads to the phrase "cirrostratus coming at us". The next warmest potential temperature air is likely to be in the middle levels of the atmosphere and bring altostratus northward but not as far north as the cirrus. The lowest layer of air comprising the warm conveyor belt creates another deformation zone enclosing nimbostratus.

Connecting all of these deformation zones into a deformation skin or veil encloses the leading edge of the warm conveyor belt. It takes about 4000 feet of cloud depth to start precipitation processes. Typically that means it takes all three layers of cloud so that precipitation starts after the lowest level deformation zone passes by.

Looking East just before sunrise - North to the left

Seeing is believing and I have been witnessing this process since I was a teenager and sometimes lucky enough to have a camera or a paint brush handy. Here are just a few.

Looking east at sunrise

Looking west from the Oak Ridges Moraine at sunset

So this is the beautiful warm conveyor belt that brings heat and moisture northward as part of the energy balance of the earth. It is one of the dancers in every cyclone that makes weather more of a ballet than a battle. There is much more to know but I will save that for another entry or two.

Warmest regards,
Phil the Forecaster

PS: Much more to come and thank you to my COMET friends in Boulder who helped publish this stuff.