Using The Short Fuse Composite to Forecast Severe Convection:

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Using The Short Fuse Composite to Forecast Severe
Convection

• Part I Ancient History The AFOS Era

By Jim Johnson Mike Umscheid NWS Dodge City, KS
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Using The Short Fuse Composite to Forecast Severe
Convection

• - - - The Dark Ages - - -
• Phil Bothwell's ADAP (NWS SR-114) piped in from
  AFOS node in 1985.
• Watched hourly ADAP charts for May 7, 1986
  Canadian, TX F-3.
• A few base charts selected by spring season of
  1987. STA, SMC, SSL and SSC.
• Charts watched for 18 TX, KS and CO Tornadoes
  1987 - 1990. Epiphany!! Nov. 15, 1988 TOP
• Empirical values noted by parameter - composite
  the charts and define a threat area.

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Using The Short Fuse Composite to Forecast Severe
Convection

• Parameters
• Flux Divergence of Surface Mixing Ratio
• Potential Temperature Advection
• Surface to 500 hPa Lifted Index
• Convective Cap
• Streamlines of Surface wind direction
• Thru 1996 total of 63 cases 81 success in
  first hour from composite time 62 in second
  hour

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Using The Short Fuse Composite to Forecast Severe
Convection

• The Short Fuse Threat Area
• Down-wind of the positive Theta advection axis.
  (ex. - Burgess, et al. BAMS, 1994)
• Within the 1.5g/kg/hr SMFC isopleth.
  (Waldstreicher, NWA Dig.,14, 1989)
• On axis of maximum instability
• Convective cap 2 degrees Celsius or less.
• Tornado Symposium III 1990 AGU Monograph 79
• Went online in 1996 heavy use by chasers

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Using The Short Fuse Composite to Forecast Severe
Convection
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Using The Short Fuse Composite to Forecast Severe
Convection
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Using The Short Fuse Composite to Forecast Severe
Convection
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Using The Short Fuse Composite to Forecast Severe
Convection
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Using The Short Fuse Composite to Forecast Severe
Convection

• TORN 1 S Amorita OK 25/0045Z
• TORN 3 ENE Amorita OK 25/0050Z
• TORN 8 E Amorita OK 25/0055z-0105Z
• TORN 6 W Medford OK 25/0146Z-0153Z
• Total 15 Tornadoes Cyclic Supercell?

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Using The Short Fuse Composite to Forecast Severe
Convection

• Change to AWIPS and associated problems MSAS
  and LAPS arent same as ADAP!
• AWIPS cant do O.A. of raw data!!
• When AFOS was unplugged, so was the composite!
• Had to find a way to apply the technique to AWIPS
  product sets - recalling that the previously
  arrived at empirical values were no longer
  valid..