Drawing a Jet Stream Map (Method 1)

Method 1 is basically finding areas of of peak wind speeds, circling them and connecting them.

Method 2 is basically following the tightly packed height contours around the trough and ridge patterns.

• The basic steps for drawing a jet stream map, whether it is an analysis or a forecast model, can be broken down in easy steps.  

• BUT REMEMBER: you don't have to be perfect.  When you are drawing a jet stream map you are making "an idealized or simplified map".  You are making a continuous line for something that, in reality, is not continuous and in fact can be displaced vertically. 

•  A good tip: if you are able, looping through several forecast hours will give you better sense how things are flowing.

• I also have a post with basic information on jet streams.

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METHOD 1

Get the Level

1. Choose the appropriate level of the atmosphere.  Generally choose charts between 300mbs to 200mbs.  In an ideal depiction, choosing a layer (or slice) of the atmosphere would be more appropriate that just taking a paper a two-dimensional plane.  But, I and you, work with what is available and in the time constraints we have.

• During cold seasons, the 300mb chart might be of better use, since the air is more cold and dense in the vicinity of the jet stream during the cool season. 
• During the warm seasons, the 200mb can be used but anywhere in that range is good.

Here is a forecast model I choose, the GFS at 300mbs, for the morning of Friday, November 15th, 2013.   It is provided by Unisys Weather

Image 3

Where are the higher winds?

2. Circle the locations of higher winds. This can be done in a couple ways.  Many forecast models show shading, like the one I choose.  There is usually a scale included (see Image 3 above).  

Sometimes models include only wind barbs.  Such as in the image below.

Image 4

In either case, start by drawing circles contours around the areas winds, generally above 50 kts to 80 kts.  Below is rough example (Image 5).  They don't cleanly hook together do they?  In the real atmosphere they usually don't.

Image 5

Find the Core

3. Draw jet core lines: within the general area of higher wind speeds done in step #2, draw lines centered at highest wind speeds, and draw them in the direction of the wind flow.   

• Generally winds flow from west to east, but can also dive from north to south or from south to north (and in some cased west to east.  

• Wind barbs, like in the example above (Image 4), are placed where the winds are coming "from". In the (Image 4) example, in the Blue Print Example, it shows northwest winds.  
• In some forecast model depicts they show arrows, like the Image 5, above.  This generally shows the direction the winds are flowing to.  
• That is a subtle difference but it is import to know, otherwise you may be "steering" your systems in the wrong direction.  

I did some loose connections in the image below (Image 6):

Image 6

Plot the Jet Stream

4.  Make an approximate Jet Stream location.

Looking at the rough connections I made above (Image 6). I begin to connect lines, making some assumptions and keeping some things in mind:

• This is an idealized map. 
• I want smooth lines.  
• I will ignore some of the more "incongruous" 
• I will follow the flow of the wind field and the 300mb height contours (the lines in white).

My approximate jet stream location is see in the image below (image 7), as the thick white line. Notice there are two basic jet streams on this map, the northern polar jet and the southern subtropical jet.  Also, notice I didn't include every area of higher winds in the jet stream (specifically the higher winds around West Virginia into southern Pennsylvania).

Image 7

Other things to keep in mind when drawing a jet stream map:

• Jet streams flow around are areas of high and low pressure in the mid-latitudes.  .
• Generally when these idealized jet stream maps are shown, think about why you want to show them? 
• Oftentimes they can be good for showing differences in air masses. 
• Generally, when I think of jet stream maps and forecasts:  if my area is north of the polar jet, I'm expecting cooler air. If my area is south of the polar jet, i'm expecting milder air.
• That is a "dirty" assumption but it is good for general usage.  
• There are other things that come into play, such as whether there is a trough of low pressure over the region or a ridge of high pressure.  A trough of low pressure coming into the area, with the jet stream axis that was formerly north of the region now pushing south, generally means a cooling trend.  The opposite generally means a warming trend.

5.  Finalize the Jet Stream location (and if you desire) make it pretty:

I would make the lines smoother, if I were doing it for television.  The base map is there for a comparison.  

Image 8

If there are any questions or if you would like more examples, just send me a message in the Contact Me Section.