How Do You Interpret a NAM Sounding?

[Larry J. Kosch]

I have heard of chasers saying this is a great NAM sounding. I saw a post on Facebook that refers to a NAM sounding as "wicked". All I see is two parallel lines, red and green, running up the scale vertically.

Can you help me with the basics? Are the two lines mentioned before supposed to stay separate or cross over at some point?? Thanks for your input!!

 

[rdale]

If they cross - then apparently the May 21, 2011 end of world predictions have come true.

Looks like you need to interpret soundings before getting into model soundings and "good" or "bad" ones.

https://www.meted.ucar.edu/training_module.php?id=225

 

[Jeff Snyder]

Larry -- I don't see a sounding in your post... Can you check to make sure the image embed code is correct?

 

[Benjamin Smith]

If they cross - then apparently the May 21, 2011 end of world predictions have come true.

Looks like you need to interpret soundings before getting into model soundings and "good" or "bad" ones.

https://www.meted.ucar.edu/training_module.php?id=225

Thanks for posting this, I had no idea there was such a quality free access program for this.

 

[Richard Dickson]

Rob,
That's a very good link to post in the Educational Forum which should help a number of folks learn more about one of the more confusing aspects of forecasting. I imagine you will receive a number of 'thank you's' even if they are not posted here.

Looks like you need to interpret soundings before getting into model soundings and "good" or "bad" ones.

https://www.meted.ucar.edu/training_module.php?id=225

 

[Drew.Gardonia]

from what I know of the soundings, the red line = temp, the green line = dewpoints. if the lines are fairly close together, then that means the temperature of the moisture in the atmosphere is relatively close to the temperature of the air in the atmosphere, which means the air is saturated, which is good for the development of storms and supercells. So an example of close soundings would be Air Temps of 80* and Dewpoints of 69*. The closer the lines are together, the more saturating of the atmosphere.

An example of a sounding where the green line and the red line are far apart would be Air Temps in the 80's and Dewpoints in the 50's or lower. Farther apart the lines are the less saturation of the atmosphere.

While the soundings do not tell the entire story, they are indicative of moisture return in a forecast. (if any of this is wrong or inaccurate please feel free to correct me, im open to constructive criticism, but this is how I understand it to be from what I've learned so far)

 

[Larry J. Kosch]

Jeff,

Sorry I didn't include one. I didn't know what a good one or a bad one was either!

 

[Larry J. Kosch]

Drew,

Thanks for your response. It makes more sense now. The closer the red/green lines are, the more moisture saturated the air is. Its possible for the two lines to meet (ex. temp 72 dewpoint 72). By determining where the moisture air packet is, you can determine if its a moisture return or cold air aloft. Thanks.

 

[jshields]

while you do want the "lines" somewhat closer together at the surface for a higher dewpoint, lines close to or overlapping at higher levels can be a bad thing. close together all the way up means a saturated atmosphere column and will likely mean precipitation= no CAPE/no severe storms. also if you have lines touching or very close together at say the 850 mb level, then you are likely going to have low level stratus clouds which means clouds and less instability as well. it's a fine balance

from what I know of the soundings, the red line = temp, the green line = dewpoints. if the lines are fairly close together, then that means the temperature of the moisture in the atmosphere is relatively close to the temperature of the air in the atmosphere, which means the air is saturated, which is good for the development of storms and supercells. So an example of close soundings would be Air Temps of 80* and Dewpoints of 69*. The closer the lines are together, the more saturating of the atmosphere.

An example of a sounding where the green line and the red line are far apart would be Air Temps in the 80's and Dewpoints in the 50's or lower. Farther apart the lines are the less saturation of the atmosphere.

While the soundings do not tell the entire story, they are indicative of moisture return in a forecast. (if any of this is wrong or inaccurate please feel free to correct me, im open to constructive criticism, but this is how I understand it to be from what I've learned so far)

 

[Greg Blumberg]

I'll quickly summarize the lines here:

Red = Temperature
Green = Dewpoint

When then two meet, you have saturation (i.e. a cloud.) In some instances in soundings from observations, the two do not have to meet in order to identify a saturated layer. There can be instrument errors that don't properly identify the dewpoint as equaling the temperature. In that case if the difference between the temperature and dewpoint is less than or equal to 5 degrees Celsius, you can have saturation.

The further apart the temperature and dewpoint are, the "drier" the air is. Lines far apart indicate a lower relative humidity, and lines that are closer indicate a higher relative humidity. If the lines touch, you have reached 100% relative humidity which is what you get when you have saturated air and a cloud.

One wants warm, moist air near the surface and cool, drier air aloft for storms. This is a gross generalization, but represents the ideal "unstable" atmosphere that many of us look for.

rdale's link for the MetEd Skew-T Mastery is a valuable educational resource that I encourage anyone on this forum to explore.

 

[jaredleighton]

from what I know of the soundings, the red line = temp, the green line = dewpoints. if the lines are fairly close together, then that means the temperature of the moisture in the atmosphere is relatively close to the temperature of the air in the atmosphere, which means the air is saturated, which is good for the development of storms and supercells. So an example of close soundings would be Air Temps of 80* and Dewpoints of 69*. The closer the lines are together, the more saturating of the atmosphere.

An example of a sounding where the green line and the red line are far apart would be Air Temps in the 80's and Dewpoints in the 50's or lower. Farther apart the lines are the less saturation of the atmosphere.

While the soundings do not tell the entire story, they are indicative of moisture return in a forecast. (if any of this is wrong or inaccurate please feel free to correct me, im open to constructive criticism, but this is how I understand it to be from what I've learned so far)

There is a lot of truth in the above quote, but soundings are quite a bit more complicated and divulge a lot more about the atmosphere than what is written above. I've seen the COMET "Skew T Mastery" link posted and I highly recommend going through that module and practicing with it. IMO that module is one of the best modules you can find on the COMET site...I digress. Atmospheric soundings, and for that matter model soundings (i.e. NAM, GFS, RUC, etc...) help to see what the atmosphere is doing in the vertical rather than the planar (surface/upper air maps). As I said earlier, there are more to the soundings than just green line close to red line. These two lines will tell you what the LCL and LFC levels are. You can determine the existence and how strong a cap is. You can determine how steep the low and mid level lapse rates are (the steeper the better for deep convection). And if you pay close attention to the direction the wind barbs veer or back with height in the atmosphere you can get a good idea about the shear parameters. And all the previously mentioned items are for severe weather. Soundings also give priceless information about the atmosphere in regards to winter weather (i.e. precip type and intensity). IMO, the atmospheric sounding may be the most important and most divulging piece of meterological data we have. The above mentioned COMET course is very helpful for determining the what in the atmosphere, but to determine the why will most likely require a college class in thermodynamics. There you will learn what the slanted lines are, why some lines curve while others don't, and why the pressure levels aren't at regular intervals.

Jared

 

[Greg Higgins]

While there are numerous "free" internet sites, there is also an excellent software program called RAOB (www.raob.com). There is the basic package and then several different add-ons depending on your wants, desires and needs. Another good quality is that the developer is constantly updating, sends out monthly "heads-up" messages and is very good with support. The manual is also a wealth of information. The drawback is that with all the add-ons, it does get a little pricey. As noted above, the Skew-T is a wealth of information, learning to understand and use that information takes time.

*****Please note, I am a satisfied user of RAOB, and do not receive any compensation for my 2 cents!!!*****