Short Fuse Composite Charts

Objective meso-analysis using hourly LAPS/MSAS analysis grids and NWS GFE software


Image of short fuse composite #1 - click to enlarge Image depicted short fuse composite #2 - click to enlarge

Chart #1:  Surface-based Moisture Convergence, Warm Theta Advection, Theta-E

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Chart #2:  Surface-based CAPE, Low Level Lapse Rate (0-2.5km AGL)

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  • LAPS/GFE Short Fuse Composite "Threat Area"
    • Within the maximum of surface moisture convergence
    • Immediately downwind of the warm theta advection axis
    • Within the axis of highest surface based instability (CAPE and Theta-E)
    • Within the region of lowest surface based convective inhibition (0-2.5km AGL lapse rate)
    • Temporal and spatial continuity of at least 3 hours of all of the above
  • More information on the original Short Fuse Composite and its utility in nowcasting initiation and location of the most intense convective storms (that can lead to potential tornado development) can be found in this paper:
    • Jim Johnson, 1993: The "Short Fuse" Composite: An Operational Analysis Technique for Tornado Forecasting.  In The Tornado: Its Structure, Dynamics, Prediction, and Hazards (C. Church, D. Burgess, C. Doswell, and R. Davies_Jones, eds.). Geophysical Monograph 79, American Geophysical Union, Washington, D.C. pp. 605-610.   Click HERE! to read document in .pdf format.
    • Discussion of the old and new technique is offered HERE.
  • Some information on the generation of these graphics:
    • The charts are currently updating at :35 past the hour.
    • The surface moisture flux convergence graphic is computed locally using MSAS hourly analysis wind fields (instead of LAPS).  MSAS uses a better quality control algorithm to filter out poor wind observations, versus the LAPS analysis scheme.  Testing has concluded that the moisture convergence field offered a better signal using MSAS winds in most convective events.
    • Warm Theta Advection, Theta-E, and CAPE graphics are all the internally calculated grids from within LAPS itself.  (Future plans are to also calculate Theta Advection using MSAS winds, but the "potential temperature advection" grid from LAPS itself tends to have less noise than moisture convergence).

  • Latest Changes & Recent Events:
    • (6/20/2005)  We have changed Chart 2 to remove surface-based CIN and use, instead, 0-2.5km AGL low level lapse rate.  A discussion on this change can be found HERE
    • (10/5/2005)   Version 1.0 of AWIPS Short Fuse Composite is now available on the NWS AWIPS Local Applications Database.
    • (10/5/2005)  A two-part Powerpoint presentation "Using the Short Fuse Composite to Forecast Severe Convection" is now available which was presented at the 2005 9th Annual High Plains Conference.
      Part I - "History of the SFC in the AFOS Era"
      Part II - "The Next Generation SFC" which includes Case Study examples from April 10, June 9, July 3, and August 19 2005. is the U.S. government's official web portal to all federal, state and local government web resources and services.