700-mb Temperatures/180-mb AGL MUCIN and Severe Weather Reports

Background:  Forecasters have considered the 700-mb temperature as a simple guide for a limit to convection since at least the 1950s.  In particular, the 10-12°C isotherms at 700-mb have been used as a loose discriminator between environments with "storms" and those with "no storms."  Although we advocate looking at other fields such as convective inhibition (CIN) or lid strength index (LSI) -- either by a sounding or plan-view display -- we also believe it is important to quantify this rule of thumb that continues to be at least moderately used.  Our goals are to (1) make people aware that a significant number of severe storms occur when the 700-mb temperature is above 10-12°C and (2) provide a climatology so forecasters have a reference when using 700-mb temperatures as a guide for "capping."

Methodology:  All NOAA Storm Data severe convective reports for March-October from 1993-2006 were obtained for the continental United States (CONUS).  Each of these 297,086 reports was then matched in time and space with the value of the 700-mb temperature from the 3-hourly, 32-km grid spacing, North American Regional Reanalysis (NARR) data.  Using ArcGIS, the maximum and average 700-mb temperature for various report combinations (e.g., all hail, sig torn, 18-06z, etc.) was derived for a roughly 80-km grid box, with the requirement that at least five reports were available per grid box (the only exception is for significant tornadoes, where only one report per grid box was required).  Additional 9-point smoothing was applied in order to allow for the strongest signals to be displayed.  Moreover, MUCIN data from the NARR have been downloaded for comparison to the severe storm reports.

Paper in Weather and Forecasting (2010).

Contact:  If you have questions or comments about information listed on this page, please e-mail Matthew Bunkers, the Science and Operations Officer at the National Weather Service (NWS) in Rapid City, SD.

 

Miscellaneous Images

  Figure 1 -- study area with the "High Plains" outlined with the thick black line

  Figure 2 -- cumulative frequency plot of 700-mb temperature vs. all severe
    reports for the High Plains (26% > 12°C)

  Figure 3 -- cumulative frequency plots of 700-mb temperature vs. monthly
    severe reports for the CONUS (6% > 12°C)

  Figure 4a -- deciles of F-scale vs. 700-mb temperature

  Figure 4b -- deciles of hail size vs. 700-mb temperature

  Figure 4c -- deciles of wind gust vs. 700-mb temperature

 

Monthly Reports vs. 700-mb Temperatures

  MaxT All
Severe
AvgT All
Severe
MaxT All
Tornado

AvgT All
Tornado

MaxT All
Hail
AvgT All
Hail
MaxT All
Wind
AvgT All
Wind
March X X X X X X X X
April X X X X X X X X
May X X X X X X X X
June X X X X X X X X
July X X X X X X X X
August X X X X X X X X
September X X X X X X X X
October X X X X X X X X

6 Panel 6 Panel 6 Panel 6 Panel 6 Panel 6 Panel  6 Panel 6 Panel

 

Significant Reports vs. 700-mb Temperatures

 

MaxT All Months

AvgT All Months
Torn X X
Hail X X
Wind X X
SigTorn X X
SigHail X X
SigWind X X
  6 Panel 6 Panel

 

Diurnal Reports vs. 700-mb Temperatures

  MaxT All Types AvgT All Types
All X X
18z-06z X X
06z-18z X X
    6 Panel

 

MUCIN results are below.
-------------------------------------------------------------------------------------------------------

Monthly Reports vs. 180-mb AGL MUCIN

 

Min
CIN All
Severe

Avg
CIN All
Severe

Min
CIN All
Tornado

Avg
CIN All
Tornado

Min
CIN All
Hail

Avg
CIN All
Hail

Min
CIN All
Wind

Avg
CIN All
Wind

March X X X X X X X X
April X X X X X X X X
May X X X X X X X X
June X X X X X X X X
July X X X X X X X X
August X X X X X X X X
September X X X X X X X X
October X X X X X X X X

6 Panel 6 Panel 6 Panel 6 Panel 6 Panel 6 Panel  6 Panel 6 Panel

 

Significant Reports vs. 180-mb AGL MUCIN

 

Min CIN All Months

Avg CIN All Months
Torn X X
Hail X X
Wind X X
SigTorn X X
SigHail X X
SigWind X X
  6 Panel 6 Panel

 

Diurnal Reports vs. 180-mb AGL MUCIN

  Min CIN All Types Avg CIN All Types
All X X
18z-06z X X
06z-18z X X
    6 Panel

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