1. Common Severe Weather Weather Soundings

2. Severe Weather Soundings
Type “A” or Inverted “V” Sounding
Most commonly found in the High Plains, Great Basin, and Desert SW
Low Humidity at most levels, but especially at lower levels
Produces Storms with very high cloud bases
Mostly Virga
Largest Severe Weather Threat:
Severe Straight-Line Winds
Dry Microbursts
Due to evaporational cooling of precipitation falling out of the cloud base

3. Severe Weather Soundings
Type “A” Sounding Cont.
Downdrafts are normally much colder than the environment and therefore more dense through a deep layer of the atmosphere
Rate of cold air production is proportional to the amount of evaporation taking place
Ratio of evaporated rain (Virga) to rain reaching the surface increases with the increasing height of the cloud bases

4. Inverted “V” Sounding

5. Inverted “V” Sounding

6. Inverted “V” Sounding

7. Severe Weather Soundings
Type “B” or Loaded Gun / Goalpost Sounding
Moist air in the boundary layer with dry air aloft
Typically found in the Central & Southern Plains
Large supply of moisture in the boundary layer provided by a low-level southerly flow (mT air)
Low-level moist convergence on the nose of a low-level jet (LLJ) (850mb)

8. Severe Weather Soundings
Very warm and dry air at mid-levels (cT air) off of the Mexican Plateau from an elevated region known as the EML or Elevated Mixed Layer
Provides a strong capping inversion which will inhibit the premature release of the convective instability
Most commonly associated with the warm sector of Spring & Fall mid-latitude cyclones

9. Loaded Gun Sounding

10. Loaded Gun Sounding

11. Loaded Gun Sounding

13. A severe weather environment that includes an EML usually results in high-end convection. Why?
The EML prevents deep, moist convection until high potential instability is achieved (bottom of EML acts as a lid or cap).
In the absence of deep, moist convection, warm, moist low level air can flow northward in an unimpeded manner (underrunning).
Tendency to keep storms from becoming overly widespread (the exception is for severe MCSs).

14. A severe weather environment that includes an EML usually results in high-end convection. Why?
Prevention of deep vertical mixing. Generally does not allow SFC dewpoints to mix out.
Very steep lapse rates in mid levels enhances CAPE = fast updraft accelerations.
DCAPE (Downdraft CAPE) enhancement

15. Elevated Heating = Steeper Lapse Rates
Cold
Cold
Warm
Cool

16. In the absence of widespread diabatic processes, EMLs are advected downstream without changing much character at all:

17. Confirming the sounding does contain an EML – trace back to source region

18. Backward trajectory analysis
SSM
ALB
Backward trajectory analysis
LBF
ELP

19. ELP 12z 25Aug73
LBF 12z 26Aug73
SSM 12z 27Aug73
ALB 12z 28Aug73

20. Severe Weather Soundings
Type “C” or Humid/SE Sounding
Found in Midwest & SE U.S. in the late Spring and Summer
Associated with a barotropic environment
Non-advection environment in which isotherms parallel isoheights/isobars
Very deep layer of moist air (mT), generally extends from sfc to at least 700mb
Very small amount of evaporation, so generally light to only moderate downdrafts
Greatest Threat: Heavy/Flooding Rains
Convection is initiated from differential surface heating and a lack of a capping inversion

21. Humid / Rain Sounding

22. Humid / Rain Sounding

23. Humid / Rain Sounding

24. Launched into Convection

25. Launched into Convection

26. Severe Weather Soundings
Wet Microburst Sounding
Similar to Type “C” sounding in that there is a deep layer of moist air
However, there is significant drying aloft
Most common in the Southern Plains, Midwest, and Southeastern U.S.
Deep layer of moisture begins at sfc and extends to approximately 700mb
Moist air is capped by a dry layer that begins at 700mb – 600mb
Dry air provides evaporative power
Get the production of negative CAPE (B-)or Downdraft CAPE (DCAPE)
This leads to intense downdrafts and downbursts

27. Wet Microburst Sounding

28. Wet Microburst Sounding

29. Severe Weather Soundings
Low-Level Jet Sounding
The low level jet is a high speed return of warm and moist air from the south or southeast; moisture source is the Gulf of Mexico
Most common and intense over the Plains states and Southeast states
The low level jet occurs in the warm sector of a developing mid-latitude cyclone in the Central and Eastern U.S.; occurs generally ahead of the cold front boundary
Intensity of low level jet is increased due to temperature gradient between cooler high elevations in the high plains compared to warmer East Great Plains at night. Can also intensify by the warm sector of a mid-latitude cyclone being east of the cold sector.

30. Severe Weather Soundings
Low-Level Jet Sounding Cont.
Low level jet adds heat, mass and momentum to developing thunderstorm and produces low level speed and directional shear (results in very high Helicity values)
Produces abundant WAA (warm air advection) that may break a weak to moderate cap. WAA produces broad synoptic scale uplift
Strongest low level jet winds are generally at the top of Planetary Boundary Layer due to less friction than at the surface
Advection may well be over 65 miles per hour

31. Low-Level Jet Sounding

32. Severe Weather Soundings
Elevated Convection Sounding
Most common in the cool season on the north side of a frontal boundary (in the cool air)
Parcels do not rise from surface during elevated convection. Parcel lapse rate on skew-T from surface is useless when the boundary layer is very stable.
Parcel will generally rise from top of temperature inversion during elevated convection. On the sounding below, a parcel rising from the 700-mb level will be much less stable than a parcel rising from the surface.

33. Elevated Convection Sounding

34. Elevated Convection Sounding

35. Elevated Convection Sounding