How to read a skew-t sounding

[tombo82685]

Im not sure if people know how to read skew-t soundings so i thought i would make a thread on a quick beginner editorial. If anyone wants to add to this go ahead because im not going to cover all the thing on the skew-t just the main things.

First off, this is a skew-t for philadelphia, pa at hr 192 off the 0z gfs.

lets go over what some of the things on this diagram stand for. The numbers on the bottom of the diagram represent the temperature in celsious. To the right are wind barbs that show wind direction at each level of the atmosphere. On the left hand side there are two sets of numbers. The one on the outside represents in mb the layers of the atmosphere. The numbers inside the graph are the elevation in meters from the surface. For instance, 850 mb, is 1356 meters above the surface or 4, 448 ft in elevation.

Now, the lines on the diagram. The solid red line on the graph is the temperature. The dotted red line is the virtual temperature. The green line is the dew point. The thin blue line is the wet bulb temperature. The solid black line that i outlined on the diagram is the freezing mark from the surface up to the upper atmosphere.

Now, i also highlighted two areas on this graph. The highlighted area to the right in red is everything above freezing. The highlighted area to the left in blue is everything below freezing. (note: i didnt highlight close to the line because you couldn't see the lines well when it was highlighted.)

Now in reading this map, lets start out at 850mb, a follow that across to the red line, we note that the 850 temperature is to the left of the black line (0 degrees C) in the blue shaded area, as well as the dew pt and wet bulb meaning at this time frame philly has a an 850 temp, dew pt and wet bulb below 0. Now lets look at the surface temperature for philly at 1000mb. Follow that to you meet the red line. We note here that the red line falls on the right hand side of the black line (0 degrees C) in the red shaded area meaning philly has a surface temp above freezing. We can also not that the wet bulb, and the dew pt are to the right of the black line (0 degrees 0)

Hopefully, this clears things up for people and you have actually learned a thing or two.

[hiker]

Thank you for this tutorial. I did learn enough to move forward.

Hiker

[Scotty Lightning]

Nice write-up there Tom.

If you'd like a more advanced tutorial, there is a Comet module available.

http://www.meted.uca...mesoprim/skewt/

[Sampson]

Every little bit helps for someone like me. Thanks for taking the time

[Aaron]

You can also figure the CCL take a line from the dew-point up the (parallel) to the sat-mixing ratio lines to the temp. Where this line intersects will normally be the height to where your clouds will form. CCL or Cloud Condensation Level.

[LocoAko]

This is a good thread and should be bumped so more people see it. There's a ton to know about Skew-T's but at least having the basics out of the way is a good thing.

Since this thread seems geared towards analyzing Skew-T's for winter, I figured I'd explain how to calculate, roughly, surface wetbulb temperatures. On the posted Skew-T, the wet bulb temperature is shown as a blue line, but it usually is not shown on a skew-t.

You can get an approximate surface wetbulb by using something called Normand's Rule.

This is done by finding the Lifted Condensation Level (take the surface dewpoint and following it up along a mixing ratio line; take the surface temperature and follow it to the upper left along a dry adiabat; the LCL occurs where these two intersect) and from that point traveling to the surface along a moist adiabat.

Knowing what the wet bulb temperature is can be important where evaporational cooling from dry air at the surface could cause it to snow or sleet when the surface temperature is above freezing. This occurred last week and to a lesser extent this past Monday. If the wet bulb temperature is below 0C, then (in general...) the snow falling into the dry air will evaporate and cool the air and make it to the surface intact.

[LocoAko]

Here is another very useful page for how to determine precipitation type using a sounding:

http://www.crh.noaa.gov/lmk/soo/docu/precip_type.php

Freezing Rain:

Sleet:

Definitely worth checking out that site.

[MacChump]

really nice thread, tombo...helped me out immensely (as did the other websites suggested by other posters)...

[jasperk99]

As a beginner I really appreciate this explanation; I have tried to understand these before and wasn't able to; this is the first explanation that has actually made sense to me.

thanks

[Quakertown needs snow]

nice work tom