Reading Water Vapour Patterns

#1282 "Singleton Sunrise-2013" Pixels Link

Patterns in the free atmosphere are created by the relative winds. These winds shape the weather as well. The system relative winds are the same as those that flow in the conveyor belt conceptual model. Historically we developed the tools to understand these patterns with respect to cloud. In the early days before water vapour imagery, clouds were all that Joni Mitchell and I had and could see.  We had to study them from both sides to really understand what they were saying. Now we can also read the invisible ink written in the skies.

GOES 4
(GOES D through H looked the same -
the number replaced the letter after launch)

Water vapour imagery came along in the 1980’s just as I was starting my meteorological career. GOES-4 was launched in 1980 and could produce imagery beyond the simple visible and infra-red. The water vapour imagery was low resolution and grainy. We were just were learning what it had to say and its "voice" was muffled. GOES-7 (GOES-H before becoming operational) was launched in 1987 and water vapour became really useful then. The same cloud patterns I was using to deduce the atmospheric relative winds could also be found in the higher resolution water vapour imagery – even in the dry air. Amazing! You can do it too.

We have been re-developing these tools from those early days in these Weather Blogs. I will summarize those methods here and you can see how they work on the water vapour imagery from Canada Day. Learning is best done by doing rather than just watching.

In the free atmosphere away from the effects of surface geography:

Linear Shapes

• Gravity waves are perpendicular to the winds like waves on a lake. Gravity waves are regularly spaced with a wavelength that increases with the speed of the wind;
• Elongated Langmuir Streaks are parallel to the winds. Generally two to four parallel Langmuir streaks can be found and they are generally larger and longer with increasing wind speed;
• Deformation Zones located at the leading edge of an air mass are perpendicular to the direction of motion of that flow. The speed of advancement of the air mass is directly related to the increasing curvature of the bow shape

Swirl Shapes

• Swirl shapes are created by rotation in the atmosphere. The three dimensional “smoke ring” in the atmosphere creates the following patterns which are mainly seen in the quasi horizontal layers of moist or dry air.
• Wind shear is simply a rotation that is moving faster than the speed of that swirl's rotation. Rotation and wind shear results in curvature in the atmospheric flow. 
• The jet stream reveals the large scale wave patterns of curvature. An upper trough is where the jet stream curves cyclonically around a southern penetration of cool air. You can think of an upper trough as a large cyclonic swirl and within it you will find smaller cyclonic swirls. An upper ridge is where the jet stream curves anticyclonically around a northern penetration of warm air. An upper ridge is a large anticyclonic swirl. It really is that simple.
• Align the fingers of your right hand with the elongated features of a swirl while pointing those fingers in the direction of the flow. Your thumb will reveal whether the atmosphere is prone to rising or sinking motion.

Cyclonic Swirls or Vorticity Maxima

• Aligning the fingers of your right hand with the flow around a cyclonic swirl will point your thumb must point upward. The air is swirling counterclockwise - cyclonically. 
• Air is typically ascending with and ahead of the cyclonic swirl. 
• Located to the left of the axis of maximum winds when looking in the same direction that the wind is blowing. 
• Typically located in an upper trough which is the equivalent of a valley in the atmosphere. Atmosphere relative winds blow with cyclonic curvature through the trough.

Anticyclonic Swirls or Vorticity Minima

• An anticyclonic swirl aligns the feature edges and the fingers of your right hand and also requires that your thumb point downward. 
• Air is typically descending with and ahead of the cyclonic swirl. 
• Located to the right of the axis of maximum winds when looking in the same direction as the wind is blowing. 
• Typically located in the crest of the atmospheric wave pattern which is the equivalent of a ridge in the atmosphere. Atmosphere relative winds blow with anticyclonic curvature through the ridge.

Additional Concepts

• Patterns get bigger with time until they dissolve away.
• Follow the flow and connect the dots where you have obvious clues to the atmospheric relative wind direction. 
• Situational Awareness and Conceptual Models - If you know the weather situation then you can anticipate the conceptual model that applies. I have only really presented the Deformation Zone the Conveyor Belt Conceptual Models but be assured, there are many more. They typically came to me on night shifts. 

Animation - Time is the Fourth Dimension

Try to view the movement of the elements relative to the mean flow of the system. It can be hard to do. The earth frame motion is the mean flow with the addition of the system relative flow. Conceptual models use the system relative flow which is what we want to understand since the relative winds shape the patterns. Situational awareness and conceptual models will help identify the system relative motion. If you know what the feature is then you know how it typically moves in the conceptual model.

Canada Day 2020 Water Vapour Image

These patterns can be found in both the moisture and the dry air of water vapour imagery and are generated in the free atmosphere by often subtle variations in wind speed or direction. These winds make the weather.

Here are a few of the shapes I saw... it is enough just to find the big ones - they are most important anyway. 

Our understanding of the atmosphere continue to improve. The movement of dry air is every bit as important as the circulations of clouds. Here is a weather information site created and maintained by my friends in Boulder, Colorado. I think you will find it very useful.

http://weather.rap.ucar.edu/satellite/ and select  Water Vapor (mid)

That's enough for today... much more to come.

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