Observing Warm Conveyor Belts and Forecasting Your Own Weather

#1717 "Sunset Waves Nite" Pixels Link

This is the last post on the warm conveyor belt before we move on to the dry conveyor belt. Exciting times for sure! The goal is to figure out just what part of the storm is about to pass your location. The warm conveyor belt is the most visible part of that storm and provides the answer. You can do this!

To become an armchair forecaster, first position yourself to look southwestward... more or less. Most warm conveyor belts approach from the southwest more or less, at least over southern Ontario. If you wish to be more exact, note the current orientation of the jet stream over your location and use that portion of the flow that lines up with the warm conveyor belt. Turn your armchair to look into the jet stream. The jet stream guides the storms and the warm conveyor belt and is the purple line in the accompanying graphic.

Apply these tips to deduce the atmospheric frame winds.

• The deformation zone has a characteristic orientation to the winds in the atmospheric frame of reference – regardless of the spatial scale of the deformation zone. If you are looking into the col, you are looking into the wind. See A Closer Look at Lines in the Sky.
•  Langmuir streaks parallel the atmospheric frame of reference winds – even though they might look like they diverge similar to crepuscular rays and train tracks… see Langmuir Streaks 
• Gravity waves your best friend and are everywhere perpendicular to the atmospheric frame of reference winds. The spacing of the gravity waves varies directly with the speed of those winds. The waves also drift in the same direction as the generating winds just like waves on a lake.

Armchair Weather Observation Platform

Now is the really fun part! You need to sit in the armchair looking directly into the approaching warm conveyor belt. Identify a characteristic piece of cloud that you hope to follow for a few minutes. 

Line that piece of cloud up with the window frame or something not moving and watch which way it drifts. In a few moments you should be able to tell which way that cloud is moving relative to your earthly vantage. Since you are already looking into the warm conveyor belt and the approaching storm, you are looking at mainly the motion of the cloud due to winds in the atmospheric frame of reference. 

If that cloud piece is moving to your right ... the cyclonic companion of the warm conveyor belt is approaching. Point the thumb of your right hand upward and see if your fingers align with any of the swirls in the cloud. There could be gravity waves in the cloud perpendicular to your fingers and the atmospheric frame winds. There should also be a considerable amount of cloud. See The Cyclonic Side of Life for more details. 

If the characteristic cloud is moving to your left, the anticyclonic companion is in line with your location. Point the thumb of your right hand downward and see if your fingers align with any of the swirls in the cloud. Gravity waves are likely in any cloud that might be present. There may not be much cloud as well and that is part of the clue. See The Relativity of the Companion Flows in the Warm Conveyor Belt for a look at the anticyclonic companion. 

If the cloud is not moving appreciably either to the right or left, you are looking directly at the col in the deformation zone. Lucky you! If there is no delta void in the cloud on the warm side of the deformation zone, then the companion vortices are less intense than average. As the companion swirls increase their spin speed with a corresponding increase in the velocity of the winds in the warm conveyor belt, moisture is increasingly spun away from the col. The delta shape becomes progressively void of moisture - another important clue to the wind speeds in the warm conveyor belt. These winds bring the heat and moisture energy to fuel the storm.  

It is typical with the approach of the warm conveyor belt that the conveyor belt pattern will continue to move along with the jet stream. You may initially see the cyclonic companion but if the storm is far away, the col and eventually the anticyclonic companion could be what you actually receive as weather when the storm eventually arrives. You will need to repeat this exercise as the storm progresses. It will mean sitting and watching the sky. I know you can do this…

You can also enjoy a satellite view of the patterns if you get tired of looking out your window. I prefer a site created by my friends at UCAR (University Corporation for Atmospheric Research) in Boulder, Colorado. Simply Google “UCAR Real Time Weather” and select the mid-level water vapour image for best results. http://weather.rap.ucar.edu/satellite/  If you follow the storm in an animation, your brain and eye will automatically focus on the relative motions of the cloud features that are created in the atmospheric frame of reference. 

Weather is important and it can also be fun! Enjoy the weather when it arrives ... evaluate your prediction (this is also called performance measurement). Have fun and learn... repeat this exercise daily. Embrace nature... it is very good for both you... and nature. 

In #1717 "Sunset Waves Nite" I recorded the leading edge of the anticyclonic companion in oils. Art and science merge. 

Warmest regards and keep your paddle in the water,

Phil the Forecaster

PS: There is no crime in updating, revising, amending or rewriting any forecast based on new observations when they become available. Doing so just indicates that there is still something to learn from nature and that your goal is to better serve your clients. :>)) Anyone who has never fixed a forecast, has yet to really write one that said something worthwhile and of potential benefit to the client. Thank you for reading and getting this far...

Storm of the Century

#2185 "Virga Singleton Sunset" Pixels Link

The 1993 Storm of the Century is also referred to as the 93 Superstorm, The No Name Storm, or the Great Blizzard of 1993. It was a large cyclonic storm that formed over the Gulf of Mexico on March 12, 1993. The storm was significant for its intensity, size, and effects all of which could be witnessed by looking at the warm conveyor belt.

I typically arrived early for my shift at the Storm Prediction Centre – ahead of traffic and certain to be on time and ready to go. I headed to any unused workstation and flipped on the water vapour network. With my coffee, I simply sat and watched the animation of the imagery. The atmosphere told me what the concern of the day might be and where we needed to expend our analysis and diagnosis energies. Our area of responsibility was huge and there were bound to be multiple concerns during the shift. The limited staff at the weather centre had to be prudent and thoughtful about workload. 

I applied conceptual models to make sense of the evolving shapes and patterns. Not only was this approach to the weather fun and stimulating but it made use of the human skill sets. Those same talents allowed us to out-compete the saber toothed tigers and other, larger and stronger creatures as we first ventured out of our caves. 

Conceptual models based on remote sensing was the approached I preferred to find the problem of the day and simply focus on that… leaving the other areas OK because there were nil problems there anyway. The satellite imagery spoke to me. I did a lot of arm waving but could not convince many of the message those satellite images might be revealing.

I would rather work the big storms. They have more to teach. The memorable storms like Hazel, Sandy and even Isabel also have more impact for safety and security. The 1993 Superstorm was such a storm!

The Storm of the Century devastated the eastern coast of North America during March 12–15, 1993. The storm killed more than 250 people as it moved from the Gulf of Mexico into Canada. It was one of the most intense mid-latitude cyclones ever observed over the Eastern North America. Snowfall totals from Alabama through Maine were tremendous. Strong winds buffeted the East coast along with extensive coastal flooding. The barometric pressures reached new lows. All of this was followed by unseasonably cold air. In terms of human impact the Superstorm of 1993 was more significant than most hurricanes or tornado outbreaks and ranks high among the deadliest and most costly weather events of the 20th century. The warm conveyor belt (WCB) told the story. 

Things to note:

• The orientation of the warm conveyor belt turned cyclonically or counter-clockwise as it rose northward. The croquet hoops illustrate this.
• Animation is required to locate the col in the deformation zone. Moisture must diverge outward from the col in the atmospheric frame of reference. 
• The tilt of the cyclonic vorticity tube in the vertical is toward the northwest. A very slow moving storm.
• The source region of the warm conveyor belt was really deep into the tropics – full of heat and moisture energy.
• The cyclonic shape of the warm conveyor belt strengthens the cyclonic companion of the WCB and the associated tiled vorticity tube. 
• Sharp contrast between the moisture fields reflects the intensity of the physical processes generating them. 
• There is much more but this is enough to reveal that this is going to be a very important storm…

Stephen King published in Storm of the Century in February 1999. The screenplay was televised as an American horror television miniseries. Unlike many other King miniseries, Storm of the Century was not based upon a Stephen King novel. It might have been based on the reality of six years previous. In the horror television miniseries a very powerful blizzard hits the fictional small town of Little Tall Island off the coast of Maine. The storm is so powerful that all access off the island is blocked, and no one is able to leave the island until the storm is over. Truth can be stranger than fiction.

Weather is important! And a good forecast can save your life... 

Warmest regards and keep your paddle in the water,

Phil the Forecaster

Langmuir Streaks – Take the time to Observe and Learn from Nature

#2203 "Langmuir Streak Sunset" Pixels Link

This is a look at the finer details in the larger flows. Even the smaller lines have a story to tell. Langmuir Streaks added to our tool box of conceptual models will give us all we need to better understand most everything we observe in a fluid.

Irving Langmuir (1881-1957) witnessed windrows of seaweed in the Sargasso Sea in 1927. His parents had encouraged him to be curious about the world and gave the advice to carefully observe nature. Apparently Irving listened and Irving constructed a conceptual model to explain his observations.

In physical oceanography, Langmuir circulation consists of a series of shallow, slow, counter-rotating vortices at the ocean's surface aligned with the wind. These circulations develop when wind blows steadily over the sea surface. Langmuir circulations circulate within the mixed shallow layer of the ocean. The helical circulations create bands of divergence and convergence at the surface. The circulation has been observed to occur up to 20° to the right of the wind in the northern hemisphere. 

I enjoyed similar patterns while paddling on inland lakes. I thought the lines of calmer water roughly paralleling the wind could be explained by the same processes described by Langmuir.
The atmosphere is just an ocean of air. When forecasting and observing the weather, one routinely observes rows of stratocumulus and cumulus in long streets paralleling the wind. Snowsqualls coming onshore off the Great Lakes have a similar structure. Why should these constructs be any different from the oceanic Langmuir Streaks?

I regularly witnessed atmospheric Langmuir streaks while I was painting warm conveyor belts en plein air in the mid 1990’s. I saw parallel streaks of cirrus that stretched along the wind direction. I wondered how those lines of thicker cloud might be explained. They were certainly not deformation zones which were and still are my go-to answer for any line in the sky. Could these cirrus formations be Langmuir processes as well?

The streaks of smoother and more reflective water I presume are the down-welling circulations induced by the wind and the associated flow in the lake. 

Langmuir streets have been well studied for their occurrence in bodies of water but pretty much ignored in the ocean of air. It surprised me that they were virtually unknown and unstudied in the world of meteorology. The processes in the gaseous fluids should be comparable if not identical to those in the seas. Langmuir streets exhibit the following.

• There is a stable layer (tropopause among many others to confine the helical circulations).
• There is a current in the fluid (jet stream among many others).
• There is a material to make the primary current and secondary circulations visible (algae, water vapour and cloud).
• Helical circulations roughly paralleling this current creates areas of convergence, divergence, updraft and downdraft.
• The natural patterns are beautiful whether in the water or in the sunset sky.

Do be honest, I have constructed vorticity chains that create elongated deformation zone skins that parallel the flow. When smoothed over time and space these deformation zones form the edges of moisture streaks in the atmosphere – a kind of continuous smoke ring – more like a smoke tube. This conceptual model could also explain the observed moisture streaks. I prefer to let nature reveal which conceptual model might be more apt.

The answer could also be found by simply examining the actual circulations of these cloud shapes in closer detail. Jochen, a wonderful friend from EUMETSAT who specialized in time lapse photography of weather as well as RGB satellite imagery, probably has the answer. We learned a lot form each other. We are both retired now but it would not hurt to ask!

Moisture patterns and conceptual models are generally scalable with the size of the atmospheric processes that create them. Vortices of all sizes behave in pretty much the same way. 

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

The Cyclonic Side of Life

#2090 "Singleton Cirrus Sunset Fingers" Pixels Link 

In “The Relativity of the Companion Flows in the Warm Conveyor Belt”  I described the anticyclonic side of the warm conveyor belt found to the right of the central streamline. The warm conveyor belt flow has distinctly different personalities on opposite sides on the dividing streamline that points straight at the col of the deformation zone. The cyclonic companion is found to the left of this dividing line when looking along the direction of the flow.  The streamlines to the left of the divide rise and curl with the fingers of your right hand as they approach the deformation zone skin.  These anticyclonic and cyclonic swirls connect as described before in the “Unified Theory of Swirls”.  But it really helps to look at them separately in a bit more detail to really understand the weather.

The cyclonic side of warm conveyor belt is perhaps the most important in the entire conveyor belt conceptual model. I will explain why. If one follows the atmospheric frame of reference wind direction from the ground in the warm sector of the storm upward while remaining to the left of the dividing streamline and col, your arm initially points from the south. When you mentally rise above the sloped warm frontal surface your arm will turn to more from the southeast. As you continue to climb in your mind, your arm will twist more to pint from the east as it reaches the level of the upstream confluent asymptote of the deformation zone. If you recreate your arm motions with height, your arm twists counter-clockwise or backs with height. Winds backing with height is equivalent to the relative cooling of the atmosphere with height. Relative cooling aloft leads to destabilization of the vertical atmospheric profile. The proverbial hot air balloon will remain warmer than the cooling air at higher heights. This unstable profile keeps the hot air balloon rising. Such an unstable profile has large impacts on the weather and the shapes of the clouds.

Gravity waves are not common in the cyclonic companion. Gravity waves require a stable layer similar to the surface of a lake. The tropopause is the stable lid on the portion of the atmosphere which contains most weather and gravity waves can always be found in the cloud there. Otherwise the clouds to the left of the dividing line of the warm conveyor belt will be more cumulus in nature. The typical cloud types and their locations are indicated in the accompanying graphic.

Note that is typical to observe a minimum in cloud within the delta void adjacent to the col. The amount of moisture being directed into this void actually decreases as the strength of the swirls in the legs of the croquet hoop increases. An intense storm will display an obvious delta void.

Individual layers of moisture are typical at the leading edge of the warm conveyor belt. As the flow continues to direct more moisture and heat energy northward, these discrete layers of moisture will thicken and merge. Precipitation processes commence when the amalgamated cloud thickness exceeds four thousand feet. At this point the integrated cloud layer is called nimbostratus - it is precipitating at the ground.

If the cyclonic side of the warm conveyor belt is sufficiently unstable, convective cloud will continue to boil upward and develop from the cumulus stage into towering cumulus and eventually cumulonimbus or thunderstorms. These unstable clouds can be embedded within the nimbostratus as is typical along the warm front. Lines of convective cloud are also characteristic along the surface cold front.

The engine driving all of this weather on the cyclonic side of the warm conveyor belt is the cyclonic side of the croquet hoop. Moisture and heat is the fuel that feeds the rotation represented by your right hand with the thumb pointing upward. When precipitation processes start, water vapour condenses re-releasing the energy it required to vapourize in the first place. The heat energy powers the rising hot air balloons.  The upward pointing thumb gets bigger more intense which in turn increases the speed of rotation represented by your fingers. In effect the rotation spins up and the cyclonic side of the croquet hoop becomes a large cyclonic tube that extends through the depth of the atmosphere.  One can imagine the prima ballerina or ice skater extending their arms upward and really going for a spin in this atmospheric dance. Moisture bands will wrap around this vorticity tube like tree rings. The number of wraps is directly related to the strength and the age of the vorticity tube.

Further the tilt of this vorticity tube in the vertical reveals the speed of the associated conveyor belt conceptual model relative to the earth. If the tube tilts upward to the east, the storm is moving the same direction as the typical jet stream which moves the weather on average from west to east. The warm conveyor belt will also and will continue to move eastward. The storm will be short-lived at any one location. If the tube tilts upward to the west, the storm will be slow moving or even stationary. The atmospheric frame winds in this case oppose the typical jet stream. Both the duration and intensity of the precipitation are likely to be significant.

I analyzed a specific warm conveyor belt pattern for an artist friend. Note the minimum in the cloud at the col. It illustrates what can be seen from the earth frame of reference. The best place to witness all of these events unfold is through water vapour satellite imagery. The magic of seeing weather evolve through the view from the satellite is where we are headed.

Remember that there is no final exam on any of this material. I present it with the sincere desire that you might enjoy nature as much as I do... we need to work with and support nature. We are all in this together!

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

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.

Weather Dances

#1714 "White Pine Island" Pixels Link

No, this is not about the Rain Dance. That is coming in a future Blog. This is all about looking at the weather in a creative and artistic way. With the fundamentals of the previous posts, you may never look at the sky in the same way ever again... and that is a good thing. 

The conveyor belt conceptual model of the wind patterns found with a mid latitude low pressure area, is fundamental to the understanding of cloud configurations. Note that the shorter term “cyclone” is frequently used to replace “low pressure area”. The idealized conveyor belts are best examined in the atmospheric frame of reference relative to the low. The atmospheric frame of reference was described in the first blog “Cloud Shapes and Lines in the Atmosphere”. 

The Conveyor Belt Conceptual Model

The atmospheric frame winds of the conveyor belts relative to the low (note that the red L should really be a red X)  are depicted by the red, orange and blue arrows of the conveyor belt conceptual model. In order to determine the actual wind experienced by an earth bound observer, these colourful winds must be added to the translational motion of the cyclone relative to the earth. Lows typically move west to east following the guiding jet stream. The difference between a rotational centre "X" in the atmospheric frame and a low in earth frame of reference was described in "Rotation is the Key to Unlock Cloud Shapes". The "L" approaches the "X" as the translational speed of the cyclone decreases. The "L" and the "X" become the same when the cyclone stops moving  relative to the earth.

For example, the relative flow of the blue CCB is typically opposite to the normal west to east motion of the cyclone. The motion of the low can thus counter the atmospheric frame motion of the CCB. In the case when the CCB is exactly equal and opposite to the motion of the low, the earth surface winds produced under the CCB must be calm – the so-called “calm before the storm”. If the actual surface winds are westerly then the low is moving faster than the CCB winds and the storm will soon pass. If the surface winds are easterly then the low is moving slower than the CCB winds. Be prepared for a longer duration and significant cyclone. The observation of the surface winds resulting from the sum of the CCB winds and the translation of the cyclone can tell you a lot about the storm. I will describe this further in a coming blog. 

Curling the fingers of your right hand in the direction of the flow at the head of each of these three conveyor belts, will point your thumb either up or down. An upward pointing thumb locates what meteorologists refer to as a positive swirl or vorticity maximum. A downward pointing thumb locates a negative swirl or vorticity minimum. Remember that these companion swirls are linked and part of the same giant smoke ring in the sky. See “The Theory of Unified Swirls”.  Bob Dylan knew that the answer was indeed blowing in the wind. You can imagine the deformation zones at the leading edge of each of these conveyor belts. See “A Closer Look at Lines in the Sky”. 

Now imagine all of this in three dimensions and mentally project the deformation zones on to the earth. You will find that the warm conveyor belt (WCB) slopes down to the warm front. The dry conveyor belt (DCB) and the cold conveyor belt (CCB) combine and project on the surface cold front. (I had to retire before all of the graphics and animations showing how the CCB and DCB might interact were completed with my friends at COMET.) In any event, fronts are the leading edges of the conveyor belts! Fronts are deformation zones! 

Jacob Bjerknes and his father, Vilhelm Bjerknes, both giants in the world of meteorology, developed the Norwegian cyclone model to explain the generation, intensification and ultimate decay of mid-latitude cyclones. The life cycle of cyclones typically follow similar stages and understanding those steps certainly aid in weather prediction. Their tremendous research was completed during the years of the First World War. They used the word “front” to describe the sharply defined boundaries between air masses. The military terminology was totally understandable.

Vilhem_Bjerknes and baby Jacob

Jacob Bjerknes

Our knowledge of air flows has increased in the last century and it might be a fine time to put a more artistic spin on this science. Weather can be more of a ballet than a battle. Every swirl and every line in the sky can be understood and appreciated for both the exquisiteness of the form and the beauty of the science that they reveal. 

Not a monster... ol' Frank and Fred and both art and science, can and should be your friend

Warmest regards,

Phil the Forecaster

PS: Much more to come.