Monday, January 17, 2022

Making Chili Science

#0839 "Cold Air Mass Cumulus" 8x10

This is the next installment in knowing the weather through observing the wind. 

I would tend to dream on quiet night shifts playing thought experiments in my mind when examining satellite imagery. The simpler the explanation, the more likely it would be to bear fruit and to circulate among the team. Here is one of my favourites. 

Imagine large pencils rolling along a table. I used colloured pencils a lot when working the forecast desk. Friction provided by the table and even a gentle push at the top gets the pencils rolling. In today's reinvention of that nightshift, we were making Chili during a snowstorm, so I used cans – same idea but tastier. 

These hand waving thought experiments from night shift required both of my hands with me looking along the direction of the wind in the accompanying graphic. Bodies are biologically constrained so that the fingers must be curled in the same orientation as the rolling pencil or bean can.

Two Cans Rolling on the Floor

Now imagine any non-uniformity like a locally stronger push on one of the cans. That push is equivalent to a locally stronger wind. This situation is exactly analogous to what happens in the planetary boundary layer (PBL) of the atmosphere. Friction at the surface slows the wind while aloft, the stronger wind is never perfectly uniform. 

Venturi Meter and Bernoulli's Principle 
Now let’s invoke Bernoulli's principle which states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure. Bernoulli said a lot more but without getting into the math, the local decrease in pressure encourages air inflow towards the locally stronger wind speeds. Air must flow from higher to lower pressure. The pressure gradient directs air inward toward my thumbs where the wind speed is stronger. 

What happens when the stronger wind speed is applied to the rolling cans over a period of time?

.
If I then turn my thumbs to align with the stronger wind of the speed increase, the thumbs must also align. The sense of rotation of the fingers from both hands, complement each other and a local updraft is created as you gaze down on your fingertips. Air convergence also creates an updraft – the air has to go somewhere! If the resultant lift is sufficient to reach the lifted condensation level for the air mass, a cumulus cloud is born. 

If we try to immerse ourselves in the atmospheric frame of reference, the local speed maximum must be shouldered by local speed minima, at least in a relative sense. On that night shift, I flipped my thumbs around to point in the opposite direction in order to simulate the relative speed minimum. This is a simple slight of hand. Do not rotate your body or move your arms.  Being biologically constrained once again, the fingers of my hand now circulated downward. The air in the local minimum was descending. If there was cloud, it was dissipating in the sinking air. 

The final step was to add the circulations formed with the local speed maxima to the speed minima. The circulations from my fingers merged together perfectly. The resultant pattern could be replicated as far as the wind regime permitted. 
A Locally Stronger Wind
Shouldered by Locally Weaker Winds

But why a line? On that night shift, I invoked the continuity equation. Air converging to a pressure decrease caused by a locally stronger wind speed can be self-sustaining. In an unstable environment that encourages the growth of cumulus cloud, the initial cumulus cloud will be guided by the wind. The conditions that caused the first cloud to form, will also result in a second and a third cloud. Before one can say “a mix of sun and cloud”, a line of cumulus guided by the wind has formed. On the bright side, a line of clear skies shoulders the street of cumulus. This pattern is simply copied and pasted across the landscape. Cloud streets happen every day... 

Snowsqualls are great examples of cloud streets
The wind rolling pencils or cans on a table top can create cloud streets parallel to those winds. This movie played out in my mind but was confirmed by the satellite image. More on these concepts to follow. 

Warmest regards and keep your paddle in the water,

Phil the Forecaster Chadwick


Tuesday, January 11, 2022

Know the Wind

 

#2221 "Singleton Squally Snow" 6"X 8" oils

Know the wind and you know the weather!

Understanding the winds in the free atmosphere was where we started a couple of years ago with "Cloud Shapes and Lines in the Atmosphere". The patterns in the sky are created by winds within the atmospheric frame of reference. The relative winds do the sculpting and the shapes are the same around the globe. Those patterns reveal the wind and those winds lead to a better understanding of the weather through conceptual models like the "Conveyor Belt" and "Isentropic Surfaces". You will find several entries on each top if you search my Art and Science Blogs. Each Blog tried to add another piece to the atmospheric puzzle. 

It is also important to appreciate the wind in the not so free atmosphere! The planetary boundary layer (PBL) is the lowest part of the atmosphere directly influenced by contact with the earth. Heat, moisture and momentum are interchanged constantly within the PBL. Friction turns the free atmosphere winds (20 to 50 degrees) while dragging the speeds down (sometimes by 50%). The surface winds you experience veer (turn clockwise in direction) and increase in speed in order to transform to the winds of the free atmosphere at the top of the PBL. 

Cumulus clouds within the PBL reveal that the air is positively buoyant. Such a happy PBL is referred to as the Convective Planetary Boundary Level (CBL). The turbulent mixing and interaction between the earth and the atmosphere can be very deep and even extend up to the top which is called that tropopause. A larger percentage of the free atmospheric winds can get to the surface in a CBL. 

Stratus clouds indicate that there is negative bouyancy within the PBL. A stably stratified planetary boundary layer (SBL) means that any exchanges of characterisitics between the earth and atmosphere occur within a shallow layer. The stable profile of a SBL limits how much free atmosphere energy can get to the surface. 

A quick look at the lowest clouds in the atmosphere will tell you what is happening in the PBL - this is the take home message. The painting from 6:00 pm on Friday February 9th, 2019 was in the wake of a very strong cold front. Multi-lake snowsqualls originating from Lake Michigan were making it as far as Singleton Lake. It was a cumulus PBL!

It was a day after a major winter storm crossed Ontario. The winds were gusting to 45 knots and perhaps stronger. I do not own an anemometer but things tend to break with wind gusts of 50 knots. The Arctic air over the Great Lakes was cold enough to create classic lake effect snowsqualls. What was very unusual was that the squalls reaching Singleton were actually originating from Lake Michigan with a bit of a boost from Lake Huron too. The weather is never dull.

The next few Blogs will develop some more observations from the planetary boundary layer (PBL)

Warmest regards and keep your paddle in the water,

Phil the Forecaster Chadwick

Monday, January 3, 2022

Where is the sun?

 

#1650 "Cloud Signs"

Where is the sun? That's an appropriate question to ask, especially during winter solstice. We need the sun for vitamin D and to lift our emotions. In real time, it is easy to find the sun most days. Just look up and you will find the bright orb in all except the darkest of overcast skies. But how to you find the sun in an image if the sun itself is not in the picture? Here are some Creative Scene Investigation tips. 

You are in luck if there is a shadow in the scene. Simply follow the elongated shadow back to the source like a sun dial and you have your answer. After that it gets trickier. 

A plein air artist typically paints with the sun on their back. There are several reasons for this. The sun feels good on your back especially on those cold and blustery days. Those same rays of warmth also illuminate the scene revealing the rich colours that might be there. The sun also lights up the canvas and the colours on the palette so that one can see the subtleties of the pigments. I tint every canvas with a colour that is complementary to the scene. That complementary tint also tones down the stark, bright whiteness of the canvas. The reflected glare off a white canvas can be as difficult and hard on your eyes as staring directly into the sun. A plein air artist rarely paints looking into the sun. If you see a back lit canvas from me, it is almost certain to be a studio work. 

If there are clouds in the image like in this example, you will also likely find your answer as to where the sun is hiding. How the cloud is illuminated reveals where the sun must be and the interpretation is really quite elementary. 

Front lit Cumulus
A cloud that is illuminated from the front must have a brighter centre while its edges and the cloud bottom must be darker. An observer of a front lit cloud has the sun on their back. The cumulus cloud on the left above is front lit. The middle of the cloud is brighter than the edges. The bright middle portion of the clouds contains billions of cloud droplets that reflect and refract all colours of the rainbow back to your eye. These colours combine to make white light. The explanation is similar to that often used to describe why whole milk is whiter than skim. 

The cloud shape also reveals the wind direction and relative speed. The upwind, arch shaped edge of the cloud is on the left indicates that the wind has a component that is blowing from the left - simple vector addition.

Back lit Cumulus
A cloud that is back lit is the direct opposite of a front lit cloud. A back lit cloud has a darker centre with brighter edges. The observer is looking toward the sun when viewing a back lit cloud. The light from the sun is forward scattered by the smaller number of cloud droplets on the edges. The dark middle portion of the clouds contains billions of cloud droplets that block much of the direct light from reaching your eye. The upwind, arch shaped edge of the cloud is on the right indicating that the wind has a component that is blowing from the right.

I took these two cumulus cloud pictures seconds apart from my kayak. The sun does not have to be visible to deduce the direction of illumination or the wind. The wind direction was the same in both images. As a result, I was looking easterly to view the front lit clouds (above left) and westerly to photograph the back lit clouds (above right). If you apply Creative Scene Investigation (CSI) just to these images, you could deduce that the timing of the pictures had to be early to mid afternoon with a light northerly wind in advance of a ridge of high pressure.

This simple observation of cloud illumination clearly reveals the location of the sun. Most people probably realized this intuitively. The cloud shape also reveals the wind direction. 

If you know any two of the following, you can easily deduce the third: sun position; time of day; direction of north. Given sunrise or sunset and with astronomical tables, the time of day and direction of view can be determined quite accurately. 

I typically include a clue about the time of day and location in the title of my art - anything to make "Creative Scene Investigation" a bit easier and more accurate. I neglected to do both in painting number 1650 - sorry. I was painting in Rockport on the St Lawrence at 1:30 pm Saturday August 29th, 2015. Here is a link to this painting on Fine Art America where I describe the details behind this plein air work. 

Keep you paddle in the water and warmest regards,

Phil the Forecaster Chadwick

Thursday, December 30, 2021

No Explanation Required

#2435 "Overcast Sunflowers"

Sometimes the art of science does not require any explanation. Colours and light just need to be appreciated even on a cloudy day. Merry Christmas and Happy New Year. "Overcast Sunflowers" speak of longer days and a new season of growth ahead. Choose to be happy. Sunflowers are the perfect inspiration at the time of Winter Solstice. 

Keep you paddle in the water and warmest regards,

Phil the Forecaster Chadwick

Tuesday, December 21, 2021

Contrail Drift

 

Contrail Headed to Pearson International
midday on Winter Solstice 2021

Practice is important. Learn the science and then apply and reapply daily. Like sunscreen. 

Science Tuesday "Weather Watching Guide - Contrails" from this past February described how contrails could talk. As a result of decades of observation, I knew what this contrail was saying. You might know the answer intuitively without refreshing the science background. It is OK to guess but clients of my meteorological predictions when I was employed by Environment Canada, preferred the science. Clients making important decisions based on those forecasts often asked "how and why" I knew something should happen. 

On another Science Tuesday, I wrote about the down-side of contrails in "Blue Sky Blues". Unnatural alteration of the natural environment was a theme of that Blog entry and many others. The 2021 ozone hole reached its maximum area on October 7, peaking at 24.8 million square kilometers – roughly the size of North America. This hole ranks as the 13th largest since 1979 and is likely still persisting into December. This leads back to the application of sunscreen. 

My goal is simply to learn more about the natural world and its laws and maybe share that information. Perhaps through science we can help protect nature and make sound, ecological practices a part of everyday life. Listening to nature is a good thing. We should all do it more often. 

Keep you paddle in the water and warmest regards,

Phil the Forecaster


Monday, December 13, 2021

Keep an Open Mind

#2564 "Singleton Sunday Thanksgiving Sunset" 
8x10

One of the most important lessons in life and particularly for a meteorologist, is to keep an open mind. New facts and contributions from the fireside chat discussion might contribute to your analysis and diagnosis. More and better facts can lead to a better prediction. Missing information in this sunset sky is an example of how you could be mislead.

As per my sunset ritual, I watched a patch of overhead altocumulus drifting southeastward. Meanwhile the atmospheric frame relative winds were southwesterly as revealed by the distinctive wind gravity waves within that cloud. Wind waves in the atmosphere are shorter wavelength with less amplitude as compared to atmospheric swells. The sky was clear to the horizon and the setting sun. "Orange sky at night, sailor's delight". The saying calls for a "red" sky but the meaning is the same. The atmosphere was dry as far as I could paint and the saying predicted a cloud free and precipitation free day to follow. I was troubled by the angle that the wind waves made with that sharp cloud edge and wondered why...

Water Vapour imagery corresponding to the
Singleton Thanksgiving sunset of #2564
In the Bible, (Matthew XVI: 2-3,) Jesus said, “When in evening, ye say, it will be fair weather: For the sky is red." No one had access to satellite imagery 2000 years ago. Jesus was well intentioned for sure but he would have been wrong in this sunset case. This is a good example of how an additional piece of data could be used to improve your prediction. 

There was a warm conveyor belt originating from the American midwest. The lateral banding of wind gravity waves could even be witnessed in the water vapour imagery. The band of moisture over Singleton at sunset was not just a random piece of moisture but the crest of a swell providing additional lift in an increasingly moist air mass. The cirrus level deformation zone was already to the northeast of Singleton. I wrote about this weather pattern in "Sunrise or Sunset - Gravity Waves and the Deformation Zone" if you wish additional information. The wind waves were at an angle to the swell crest for a very good reason as will explained by the following graphic. 

Satellite Overview of the Cyclonic Companion (left) and the Anticyclonic Companion (right
Separated by the Jet which is near the centre of the Warm Conveyor Belt

Closer View of the Anticyclonic Companion with the
Cloud Enhanced in the Swell and Wind Wave Crests
Looking Downward from the Satellite View
An Example of Constructive Interference

Conceptual Model Compared to the 
Water Vapour View - A Match
(Close Counts in Meteorology)

The portion of the conceptual model that is displayed in any given weather situation is dependent on the relative amplitudes of the swell and wind gravity waves and the lifted condensation level of the atmosphere. The circulations are always present but without water vapour or condensed cloud droplets, they are invisible.

The following graphic places the Singleton view of the small portion of the deformation zone within the larger scale Conveyor Belt Conceptual Model.  

The Three (Four) Dimensional Atmosphere can 
be a Challenge to Interpret - Even for the Experts

To recap: The patch of moisture that I painted was drifting southeastward  as part of the anticyclonic companion flow of the conveyor belt conceptual model. This pattern is typical given our location in eastern Ontario (the yellow star in the graphic) and the fact that most emergent weather systems approach from Colorado or the Gulf of Mexico. Singleton typically sees the anticyclonic companion of the approaching storm first. 

The sharp back cloud edge that I painted was the western edge of the crest of an atmospheric ocean  swell. The enhanced bands within that swell crest were wind wave crests in the anticyclonic flow. The fact that the wind crests made an angle with the swell edge revealed that there were two different processes at work. Dynamic forces in the atmosphere create the weather that we enjoy and the approaching conditions were not fair. 

Note that the double cyclonic DZ in the above analysis is entirely within the upper trough while the bowed DZ stretches from the upper trough to the downstream ridge that is east of Singleton. Also note that there is more cloud (upward vertical velocity) associated with the cyclonic companion of the conceptual model than the anticyclonic branch. That is enough information for now - no need to go down the satellite detail, rabbit hole even if there is so much more to see and understand ... One satellite image could keep me busy for hours... 

With these new pieces of data, one must amend the Biblical forecast for the following day from "fair- sunny with no rain" to "cloudy with rain"... This is a actual example of a specific weather situation and a real painting. I was thinking "red sky at night" when I did that art although I was troubled by that angle of the wind waves. The take home message is that nature is always right. Our interpretation could be faulty if we do not listen to all of the facts.  

#2564 "Singleton Sunday Thanksgiving Sunset"
In Progress - Starting tithe the meteorology
There is no shame in amending a forecast (or a painting for that matter) ... I have amended a forecast once or twice during my career (humour intended - the only time when I did not revise a prediction was on a day-off). The crime would be in not using all of the available data and providing a better service. Keeping an open and inquisitive mind is a big part of learning and helping others. 

The clouds always tell the truth even if humans might not fully understand. I paint what I see and nature always makes sense even if it might take some effort to unravel those lines in the sky. 

Keep you paddle in the water and warmest regards... 

Phil the Forecaster Chadwick

Monday, December 6, 2021

Lines in the Atmospheric Ocean

# 2570 "Cirrus Sunset from the
Bottom of the Atmospheric Ocean"

In the previous blog "Finding Deformation Zones", I promised more art and less science for this Science Tuesday. I used painting number 2570 "Cirrus Sunset from the Bottom of the Atmospheric Ocean" to illustrate how to best find those deformation zones - but I did not explain the art within the context of that art. The sunset sky from Wednesday October 27th, 2021, was an example of a double cyclonic deformation zone embedded in a very large upper trough of low pressure and a nearly stationary southerly flow. The lines in that sunset sky did not easily reveal these truths and I promised to provide an explanation. 

Enjoying this Singleton sunset made me really ponder the orientation of these particular lines in the sky. The complexity of the patterns really emphasized that we do indeed reside at the bottom of a very deep and very dynamic ocean of air. The answers were not immediately obvious. I need to explain this sunset a bit. 

Observing from our Earthly viewing platform reveals the following. There were at least three bands of cirrus above Singleton with clear skies beyond them at least as far as the western horizon. The far edge of the westernmost cloud edge was sharp and  had to be a deformation zone but something was unusual. The well-defined cloud edge was on the western flank of the cirrus band and the moisture was to the east of the deformation zone. Gravity wind waves were embedded within the three swells of cirrus. Remember that long, wavelength ocean swells propagate great distances from their windy source. I was attributing the three bands of cirrus to be atmospheric swells. 

The meridional flow of the jet stream
 revealed a southerly
flow from the Gulf of Mexico
over all of Ontario. 
The drift of the cloud within the bands was from south so the atmospheric winds had to be southerly. Wind gravity waves embedded in the swells were consistent with the earth observation of southerly winds. Some faint ice crystal virga wafted toward the ground while catching the last rays of the setting sun. These trails of virga were in front of the cirrus swells from my vantage. The augmented updrafts where the crests of the wind waves overlap with the crests of the swells, are where you are most likely to find virga. Weather typically exhibits these wavelength properties. 

The dark sunset colours low on the horizon were the glow of the setting sun catching dust in the boundary layer of the atmosphere, stirred up by a daytime of wind and human activities. Smoke and the exhaust of industries from around the busy ports of the Great Lakes would easily explain those somewhat murkier colours. 

To complete the diagnosis of the sunset sky, I would have to consult the view from space. The water vapour imagery confirmed the orientation of the deformation zone over Singleton. But the weather story was even more complex. I was viewing just a small portion of a much larger double cyclonic deformation zone. That line in the sky was associated with an upper cyclone near Timiskaming and a second low well southeast of Cape Cod. Recall that double cyclonic and double anticyclonic deformation zones tend to be nearly stationary with respect to the globe. The next morning dawned cloudy and the satellite imagery confirmed that the pattern had even retrogressed toward the west, bringing the overcast skies with it. The jet stream was in a highly meridional flow pattern consistent with that expected from a weakening flow associated with climate change. 

The area of the water vapour imagery where I sketched in the double-cyclonic deformation zone conceptual model, shows a stronger northeasterly flow actually sinking as it headed southward. The cyclonic x's were actually 3D vortex tubes stretching through the depth of the atmosphere. The moisture over Singleton marked by the little yellow star, was actually rising as it headed northward. This pattern was not moving far but was likely to shift to the southwest with the stronger winds as I noticed the following morning. 

Classic Water Vapour Imagery revealing 
the Meridional Flow Pattern

The highly contorted flow revealed by the water vapour imagery, was typical of the wave number seven of the weakening jet stream. Instead of following the lines of latitude as a zonal, strong current of air, the jet stream was more likely to follow the meridional lines of longitude northward and then southward again in a series of ox-bow lakes. That kind of pattern was over Singleton in that sunset sky and it also told the story of climate change. 

This sunset weather story was unusual in that the weather was approaching Singleton from the east. The typical progression of weather from the west was upset and I think this would cause the viewer some anxiety although they might not really comprehend why. I remember stories of ancient peoples being terrified at the sight of an eclipse. We are not much different. At one time, these strongly blocked and convoluted patterns were very rare. 

RGB imagery like this Nighttime Microphysics
Image, combines several channels and typically
complex combinations of channels to the red, green,
and blue colours. The physical properties of the
earth-atmosphere system are better understood
by using both colours and tones to paint the data.

Satellite imagery reveals details and complexities that could keep professional meteorologists entertained for days. I know that from experience! Most people should not venture down that rabbit hole. Always remember that the atmosphere is a complex three or four dimensional flow. It is sufficient to just understand the big picture, at least to start. 

The clouds always tell the truth even if humans might not like to hear it. I paint what I see and nature always makes sense even if it might take some effort to unravel the lines in the sky. 

Keep you paddle in the water and warmest regards... 

Phil the Forecaster Chadwick




Monday, November 29, 2021

Finding Deformation Zones

#2570 "Cirrus Sunset from the Bottom of the Atmospheric Ocean"
October 2021, 11x14

If you want to find deformation zones, it really helps if you know where to look!  It is best to start with the entire globe and gaze down from space - the satellite view of the atmosphere. 

The world has changed much since I became a meteorologist in 1976. Atmospheric scientists were well aware of the impacts of fossil fuels consumption on the atmosphere as early as 1824.  I wrote about the history of climate change science in "True Confessions from Singleton Philly". I updated the current state of climate change, where we are headed and why in "The Weather Makers by Tim Flannery - Become Informed and Involved in a Good Way" and "The Weather Makers  - What has happened in Fifteen Years?". Mankind is rewriting climate which is the average weather, with each passing year. To witness these impacts in a single lifetime is unthinkable. Deformation zones are just another indication that this is true. 

All of the deformation zone flavours are on the increase with climate change. The poles are warming up much faster than the equator as the snow and ice melts to expose darker, less reflective surfaces. These low albedo surfaces absorb the sun's energy and in turn, warms the atmosphere. The temperature difference between the equator and the poles drive the jet stream. As a result, the jet stream is transforming more into a meandering trickle than a fast flowing river of high speed air. The ox bow patterns of the weakening jet stream are the perfect place to create swirls and deformation zones.

Historical Jet Stream Left - Weaker Jet Today Right

The distribution of the mountain ranges and oceans of the earth also play important roles in deviating the atmospheric currents. As a result the preferred number of waves around the globe is seven. That means that seven troughs of low pressure are separated by seven ridges of high pressure along a line of mid-latitude encircling the globe. You can safely expect a predominance of cyclonic swirls in those troughs and anticyclonic swirls in the ridges. Your extended Coriolis Hand with its fingers pointing with the flow, will convince you that this is true. 

Where to Find the Different Flavours of Swirls

Where do cyclonic swirls dominate? Cyclonic swirls can be found in upper troughs of low pressure in the atmosphere. The trough is the red area in the above graphic. 

Where do anticyclonic swirls dominate? Anticyclonic swirls can be found in upper ridges of high pressure in the atmosphere. The ridge is the blue area in the above graphic. 

Double Cyclonic Deformation Zone -
Big X added to another Big X
A deformation zone that is wholly within a trough will look like a backward s – a double cyclonic DZ. Such a deformation zone is typically generated by a flow that is associated with ascending warm air moving toward the north. I wrote about that process in "Cloud Edge Shapes - The "Backward S" Deformation Zone" and also "Warming Winds and Deformation Zones". The beauty of a conceptual model is that having worked through the theory a few times, you can appreciate what a pattern means by simple observation. You do not need to reinvent the conceptual model every day. If you witness a line in the sky that is a double cyclonic DZ, then you are in a trough of low pressure with warming weather. 

Double Anticyclonic Deformation Zone -
Big N added to another Big N

A deformation zone that is wholly within a ridge will look like an s – a double anticyclonic DZ. Such a deformation zone is generated by a flow that is associated with descending, cold air moving toward the south. 

Winds that veer (turn clockwise) with height and/or time will generate a double cyclonic DZ. Similarly winds that back (turn counter-clockwise) with height and/or time will generate a double anticyclonic DZ. 

A larger deformation zone that spans a trough into a ridge with a bowed shaped pattern pointing northward (and rising) is characteristic of a large warm conveyor belt and a storm. Similarly a deformation zone that spans a ridge into a downstream trough with a bowed shaped pattern pointing southward (and sinking) is characteristic of a large cold outbreak following in the wake of a storm.  

Bowed Deformation Zone -
Big X added to a Big N

The best place to view these deformation zone is certainly water vapour satellite imagery. Typically, one can only few a small segment of a deformation zone from the ground. From space, one can see the entire conceptual model at work.

Jim Day Rapids Double Anticyclonic DZ

For those who are interested, the same patterns can be seen not only in duckweed, but also in oatmeal and your coffee cup if you use cream. In fact, every fluid can be investigated and better understood by applying these conceptual models. 

Coffee and Cream Swirls and Deformation Zones

The shape of the lines in the sky tell the story of the weather. The vocabulary of these tales has been developed in the past few Blogs. It took me many Night Shifts when the weather was quiet (which was not often), to piece all of this together. Some of this material can be found in various Modules on the COMET Website. The rest is being presented here for the first time although this material was certainly the content of many fireside chats in the Weather Centre when the team was determining what the concern of the day would be and where the resources would be most wisely allocated. 

This content has been a bit more meteorological and scientific that I had intended but it illustrates just how much information can be gleaned from those lines in the sky. I will return to more art than science in the next Blog. 

Keep you paddle in the water and warmest regards... 

Phil the Forecaster Chadwick


Monday, November 22, 2021

Deformation Zone Flavours

#1828 "Just Another November Sunset"

What can the shape of the deformation zone reveal? How are these different shapes created? Deformation zones come in three flavours and they are all very different but all equally tasty. 

It is helpful to examine each confluent asymptote separately. If the confluent asymptote is curved cyclonically, the vorticity maximum or cyclonic swirl is the stronger of the paired swirls on either side of that confluent asymptote. 

Cyclonic Asymptote - The Red X Swirl Stronger 
in the Paired Swirls across the Asymptote
Let's Call this Asymptote Pattern "Big X"

If the confluent asymptote is curved anticyclonically, the vorticity minimum or anticyclonic swirl must be the stronger of the paired swirls on either side of that confluent asymptote. It is really that simple but it was a challenge to explain this stuff back in the nineties. 

Anticyclonic Asymptote - The Blue N Swirl Stronger
in the Paired Swirls across the Asymptote
Let's Call this Asymptote Pattern "Big N"

Now let's put a  "Big XAsymptote Pattern together with a "Big N". Aside from my clumsy graphics, this pattern is the same as the paddle swirl in the duck weed from Sunrise or Sunset - Gravity Waves and the Deformation Zone. This deformation zone pattern is typically called a "bow" as in "bow and arrow".  

"Big X" Asymptote Pattern together with a "Big N"
The Bowed Deformation Zone

Now let's put a  "Big XAsymptote Pattern together with another  "Big X".

"Big X" Asymptote Pattern together with another  "Big X"
The Double Cyclonic DZ

Now let's put a   "Big N" Asymptote Pattern together with another   "Big N". You guessed it already! This isn't so hard... 

"Big N" Asymptote Pattern together with another  "Big N"
The Double Anticyclonic DZ

One more thing, the Coriolis force that helps to create the swirls, is strongest at the poles and zero at the equator. You can easily prove this to yourself. 

Imagine yourself standing at the equator with your arms outstretched - one arm pointing north and the other pointing south. In a full day of earth’s rotation, you will experience no rotation at all. 

Now do the same thing at say the North Pole. You will note that both of your outstretched arms must point south. You will rotate with the full measure of the Earth’s rotation. It is certainly no coincidence that when you direct the fingers of your Coriolis Hand in the direction of the Earth's rotation while at either the South or North Pole, that your Coriolis Thumb points upward. Nature always makes sense if we take the time to understand. 

The swirls that shape the confluent asymptotes are much stronger at higher latitudes than they are at the equator as a result of the Coriolis force. The shapes of those swirls reveal much about the weather but we will save that for the next day. It is enough to taste the three different favours of the deformation zone conceptual model in one sitting. This might explain why I really enjoy the weather and meteorology of the high latitudes. The cloud and moisture patterns are full of stories just waiting to be read. 

Keep you paddle in the water and warmest regards... 

Phil the Forecaster Chadwick