# Presentation: 471215

## Some Applications of Indices to Forecasting

- 12th Great Divide Workshop, 10/7/2008
- Matthew J. Bunkers, SOO Rapid City, SD

## Outline

- Make note of several “indices”
- Discuss utility & attributes of indices (+ / -)
- Show several examples of testing indices for operations – implications for training

## A cornucopia of “indices”

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

***** Can be calculated over many different layers/levels/parcels

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

## A cornucopia of “indices”

- Lifted Condensation Level (LCL)*

- Level of Free Convection (LFC)*

- Equilibrium Level (EL)*

***** Can be calculated over many different layers/levels/parcels

- Moisture Flux “Convergence” (MFC)*

- Equivalent Potential Temperature (e)*

- Precipitable Water (PW)*

- Warm Cloud Depth (WCD)*

- Wet Bulb Zero (WBZ)

- Melting Level (MLT)

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

## A cornucopia of “indices”

- Convective Available Potential Energy (CAPE)*

- Convective Inhibition (CIN)*

- Bulk Richardson Number (BRN)*

- Storm-Relative Helicity (SRH)*

- Bulk Vertical Wind Shear*

- Total Vertical Wind Shear*

- Storm-Relative Wind*

- Downdraft CAPE (DCAPE)

***** Can be calculated over many different layers/levels/parcels

- Normalized CAPE (nCAPE)*

- Bulk Richardson Number Shear (BRNSHR)

***** Can be calculated over many different layers/levels/parcels

- Lifted Condensation Level (LCL)*

- Level of Free Convection (LFC)*

- Equilibrium Level (EL)*

- Moisture Flux “Convergence” (MFC)*

- Equivalent Potential Temperature (e)*

- Precipitable Water (PW)*

- Warm Cloud Depth (WCD)*

- Wet Bulb Zero (WBZ)

- Melting Level (MLT)

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

## A cornucopia of “indices”

***** Can be calculated over many different layers/levels/parcels

- Dry Microburst Index (DMI)

- Theta-E Index (TEI)

- Wind Index (WINDEX)

- Wet Microburst Severity Index (WMSI)

- Microburst Day Potential Index (MDPI)

***** Can be calculated over many different layers/levels/parcels

- Convective Available Potential Energy (CAPE)*

- Convective Inhibition (CIN)*

- Bulk Richardson Number (BRN)*

- Storm-Relative Helicity (SRH)*

- Bulk Vertical Wind Shear*

- Total Vertical Wind Shear*

- Storm-Relative Wind*

- Downdraft CAPE (DCAPE)

- Normalized CAPE (nCAPE)*

- Bulk Richardson Number Shear (BRNSHR)

- Lifted Condensation Level (LCL)*

- Level of Free Convection (LFC)*

- Equilibrium Level (EL)*

- Moisture Flux “Convergence” (MFC)*

- Equivalent Potential Temperature (e)*

- Precipitable Water (PW)*

- Warm Cloud Depth (WCD)*

- Wet Bulb Zero (WBZ)

- Melting Level (MLT)

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

## A cornucopia of “indices”

- LSI = Lid Strength Index

- DCI = Deep Convective Index

- TQ Index = for “low-topped
- 	     instability”

- HI = Haines Index*

- HMI = Hybrid Microburst Index

- Dry Microburst Index (DMI)

- Theta-E Index (TEI)

- Wind Index (WINDEX)

- Wet Microburst Severity Index (WMSI)

- Microburst Day Potential Index (MDPI)

- Convective Available Potential Energy (CAPE)*

- Convective Inhibition (CIN)*

- Bulk Richardson Number (BRN)*

- Storm-Relative Helicity (SRH)*

- Bulk Vertical Wind Shear*

- Total Vertical Wind Shear*

- Storm-Relative Wind*

- Downdraft CAPE (DCAPE)

- Normalized CAPE (nCAPE)*

- Bulk Richardson Number Shear (BRNSHR)

- Lifted Condensation Level (LCL)*

- Level of Free Convection (LFC)*

- Equilibrium Level (EL)*

- Moisture Flux “Convergence” (MFC)*

- Equivalent Potential Temperature (e)*

- Precipitable Water (PW)*

- Warm Cloud Depth (WCD)*

- Wet Bulb Zero (WBZ)

- Melting Level (MLT)

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

## A cornucopia of “indices”

- Energy-Helicity Index (EHI)*

- Vorticity Generation Parameter (VGP)*

- Supercell Composite Parameter (SCP)*

- Significant Tornado Parameter (STP)*

- Significant Hail Parameter (SHIP)

***** Can be calculated over many different layers/levels/parcels

- Significant Severe Parameter (SSP)

- Strong Tornado Parameter (STP)

- _Indices of Indices (“Inbreeding”)_

- LSI = Lid Strength Index

- DCI = Deep Convective Index

- TQ Index = for “low-topped
- 	     instability”

- HI = Haines Index*

- HMI = Hybrid Microburst Index

- Dry Microburst Index (DMI)

- Theta-E Index (TEI)

- Wind Index (WINDEX)

- Wet Microburst Severity Index (WMSI)

- Microburst Day Potential Index (MDPI)

- Convective Available Potential Energy (CAPE)*

- Convective Inhibition (CIN)*

- Bulk Richardson Number (BRN)*

- Storm-Relative Helicity (SRH)*

- Bulk Vertical Wind Shear*

- Total Vertical Wind Shear*

- Storm-Relative Wind*

- Downdraft CAPE (DCAPE)

- Normalized CAPE (nCAPE)*

- Bulk Richardson Number Shear (BRNSHR)

- Lifted Condensation Level (LCL)*

- Level of Free Convection (LFC)*

- Equilibrium Level (EL)*

- Moisture Flux “Convergence” (MFC)*

- Equivalent Potential Temperature (e)*

- Precipitable Water (PW)*

- Warm Cloud Depth (WCD)*

- Wet Bulb Zero (WBZ)

- Melting Level (MLT)

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

## A cornucopia of “indices”

- Vorticity Generation Parameter (VGP)*

- Supercell Composite Parameter (SCP)

-   This list is not nearly exhaustive!

- K Index (KI)

- Total Totals (TT)

- Severe Weather Threat (SWEAT)

- Lifted Index (LI)*

- Showalter Index (SI)

- Lapse Rate (LR)*

- CAP Strength (700 mb LI)

- Relative Humidity (RH)*

- Lifted Condensation Level (LCL)*

- Level of Free Convection (LFC)*

- Equilibrium Level (EL)*

***** Can be calculated over many different layers/levels/parcels

- Moisture Flux “Convergence” (MFC)*

- Equivalent Potential Temperature (e)*

- Precipitable Water (PW)*

- Warm Cloud Depth (WCD)*

- Wet Bulb Zero (WBZ)

- Melting Level (MLT)

- Convective Available Potential Energy (CAPE)*

- Convective Inhibition (CIN)*

- Bulk Richardson Number (BRN)*

- Storm-Relative Helicity (SRH)*

- Bulk Vertical Wind Shear*

- Total Vertical Wind Shear*

- Storm-Relative Wind*

- Downdraft CAPE (DCAPE)

- Normalized CAPE (nCAPE)*

- Bulk Richardson Number Shear (BRNSHR)

- Dry Microburst Index (DMI)

- Theta-E Index (TEI)

- Wind Index (WINDEX)

- Wet Microburst Severity Index (WMSI)

- Microburst Day Potential Index (MDPI)

- Energy-Helicity Index (EHI)*

- Vorticity Generation Parameter (VGP)*

- Supercell Composite Parameter (SCP)*

- Significant Tornado Parameter (STP)*

- Significant Hail Parameter (SHIP)

- Significant Severe Parameter (SSP)

- Strong Tornado Parameter (STP)

- _Indices of Indices (“Inbreeding”)_

- LSI = Lid Strength Index

- DCI = Deep Convective Index

- TQ Index = for “low-topped
- 	     instability”

- HI = Haines Index*

- HMI = Hybrid Microburst Index

- Mesoscale Convective System Forecast Index (MCS Index)   a recent index published in WAF (2007)

## What’s a forecaster to do?

## Outline

- Make note of several “indices”
- Discuss utility & attributes of indices (+ / -)
- Show several examples of testing indices for operations – implications for training

## Attributes of indices

## Benefits of indices

- Can summarize large amounts of data
- Can quickly draw attention to “critical” areas for further diagnosis
- Both are attractive when under time pressure

## Index limitations

- Not necessarily forecast parameters; may be diagnostic (e.g., SPC meso page)
- Diagnostic variables give current state(≠ /t), where  = STP, SCP, CAPE, etc.
- Most indices are not rigorously developed or validated – arbitrarily combined variables

## Index limitations

- Can lead to faulty perceptions of atmosphere via over-simplification
- Little value in isolation; different combos can produce similar values
- Flavor of the parameter? (e.g., EHI and its inputs)
- Constituents can evolve quasi-independently
- Action often occurs at “The Edge” – next three slides

## The Edge:  20 Jun 2006 – Rushville, NE

**LSCP**

- Tornadic left-moving supercell

**(1-EF1)**

****

## The Edge:  16 Sep 2006 – Rogers, MN

- The Edge:  16 Sep 2006 – _Rogers_, MN

**(1-EF2)**

## The Edge:  28 Feb 2007 – Eastern KS

**(1-EF4)**

- Important to train new forecasters not to focus on bulls-eyes.

## Outline

- Make note of several “indices”
- Discuss utility & attributes of indices (+ / -)
- Show several examples of testing indices for operations – implications for training

## Example of testing an index

- Jirak and Cotton (2007, WAF)
- MCS index for conditional development of MCSs
- Function of “best” LI, 0-3km shear, and 700mb Tadv
- Convert terms to standard normal and summed
- Appears to be physically based
- Developed using NARR data
- Tested at WFO Rapid City and found problems
- Operational datasets produced different results
- Didn’t implement at our office

## MCS index on WES

- _Image_ = MCS index
- _White lines_ = 700mb Tadv
- MCS index and 700mb Tadv looked very similar
- Was “verified” with 20 cases

## MCS index testing

- Let _LI_ vary from +3 to -12 (C)
- Let _shear_ vary from 0 to 25 (m s-1)
- Let _Tadv_ vary from -1 to +2 (C hr-1)

- Std Dev

- Mean

- Means and standard deviations based on NARR dataset (JC07).

## Three terms of MCS index

- Using JC07’s equation and reasonable ranges for the 3 terms
- Ideally all 3 lines should be the same

## MCS index summary

- LI component  -2 to 2
- Shear component  -2 to 2
- Tadv component  -4 to 6 (should be -2 to 2)
- NARR data underrepresented the operational Tadv range
- MCS index basically proxy for 700mb Tadv
- _Conclusion_:  not suitable for operations (authors updating to use stddev of range)

## Outline

- Make note of several “indices”
- Discuss utility & attributes of indices (+ / -)
- Show several examples of testing indices for operations – implications for training

## The STP index

- Thompson et al. (2003, WAF)
- Significant Tornado Parameter (STP)
- Mean-layer CAPE (MLCAPE, lowest 100mb)
- 0-6km shear vector magnitude (SHR6)
- 0-1km storm-relative helicity (SRH1)
- Mean layer LCL (MLLCL, lowest 100mb)

## Let’s test this

- Estimate valid ranges and calculate each term
- _For example_:  MLCAPE ~ 100 to 5000 J kg-1
- Term 1 thus ranges from 0.1 to 5
- (100/1000) = 0.1
- (5000/1000) = 5

## Versions of the STP

## Versions of the STP

## Versions of the STP

- If you use them, know your indices!

## Outline

- Make note of several “indices”
- Discuss utility & attributes of indices (+ / -)
- Show several examples of testing indices for operations – implications for training

## Supercell Composite Parameter (SCP)

- Function of MUCAPE, Eff. Shear, and Eff. SRH
- Can run similar tests as for the STP
- Testing suggests SCP can be misleading

## SCP Potential Pitfall

- Dominant right-mover

## Modeling Results

- SRH (RM) = 62
- SRH (LM) = -226

- Hodograph didn’t turn enough in lowest 36 km to strongly favor LM.

- Environmental heterogeneity and low-level wind variability also factors.

## Outline

- Make note of several “indices”
- Discuss utility & attributes of indices (+ / -)
- Show several examples of testing indices for operations – implications for training

## Example of coord system sensitivity

## Supercell motion example:  BUFKIT

- Bunkers et al. (2000)
- Non-weighted MW for supercell motion, every 500 meters
- BUFKIT
- Uses ALL data for MW; produces low-level bias
- Supercell motion often too slow...so beware of BUFKIT algorithm!

## SCM:  Excel vs. BUFKIT

**12-kt difference between the two!**
**        ...****but AWIPS is okay**

**275° 28 kts**

## Summary for indices

- Look at the raw data (e.g., surface maps, soundings, 0-1km shear, MLLCL, etc.)
- View the indices’ constituent components (e.g., 4-panel mode)...”*STP = 2 means what?*”
- Test new indices before implementing them in operations (e.g., the MCS index)
- Folly to develop indices away from operations

## One final thought

-  “*The author’s most regrettable severe storm forecast mistakes have arisen from ignoring data that were relevant to the daily diagnosis...and/or failing to complete the diagnosis on what initially appeared to be a benign weather day.*”
- 	 – Al Moller (2001, Severe Convective Storms Monograph)
- Analysis and diagnosis of observational data is critical – yet this has become a lost art.