Summary15 total heavy rain events

– All but 1 event showed a positive direct relationship

– 10 are positively correlated, with p=0.05

EPEC over-forecasted many heavy rain events

– POD is high, so EPEC is likely to identify threat area

– EPEC has a positive relationship with heavy precipitation

EPEC values for typical heavy rain events > mean EPEC values as well as 1 s.d. above mean

Guidelines regarding proper employment for the EPEC tool

– Reliable ingredients for heavy rainfall w/elevated convection

• A thermal boundary (often a stationary front)

• A jet streak northeast of heavy rainfall location

• Deep tropospheric moisture north of surface front

• EPEC >74 employed only on cold side of Θe gradient

Evaluated at the 2016 WPC FFaIR summer testbed:“Overall, the EPEC Index, used during FFaIR as a way to diagnose elevated

convection that may lead to heavy rainfall and flash flooding, was

positively reviewed as a good situational awareness tool.”

Currently available in real-time via: http://sensibleweather.com

EPEC: A Tool for Anticipating Excessive Precipitation

with Elevated Thunderstorms

Alzina Foscato1,2, Patrick S. Market 1, Neil I. Fox1

1 Department of Soil, Environmental, and Atmospheric Sciences, University of Missouri2 National Weather Service, Rapid City, SD

IntroductionAttempting to predict the location and the initiation of elevated

thunderstorms can be very challenging due to the uncertainty in of the

mechanisms that release elevated instability (Moore et al., 2003)

McCoy (2014) extended the Moore work with composite means and

variability Larger case sample, BUT

Lower rain threshold

2.00 inches (50.4 mm) / 24 hours

McCoy (2014) identified a few unique patterns with heavy-rainfall-

producing elevated thunderstorms:Strong signal; strong variability

- Upper-level jet streak to the northeast of the region

Divergence > 3 x 10-5 s-1 (lift)

- Event located within or just south of 850-mb θe advection

maximum (convergence max)

- Signals LLJ from the SSW (moisture; lift; instability)

Strong signal; small variability

>30 K-index values (instability)

Precipitable water values > 1.6” (moisture)

2-m θe pattern (confirms elevated convection)

Purpose

The Excessive Precipitation with Elevated Convection (EPEC) tool was derived

from the mean and interquartile ranges from McCoy’s (2014) results.

– Used during 2014 to 2015, forecasting for field phase of the Program of Research

on Elevated Convection with Intense Precipitation (PRECIP) project

– EPEC tool was critical for identifying where heavy rainfall would occur

EPEC tool was created to aid in identifying where heavy rainfall with elevated

convection may occur

– Discriminate surface-based from elevated convection using low-level θe field

• 2-m or 950-mb

Objectives

Verify that the EPEC tool can be a predictive parameter for flash flooding.

Create verification statistics on the EPEC tool

- Doswell and Schultz (2006) discussed requirements that a proper forecast

parameter should meet

• Verify with a contingency table

– Threshold values

• Test the skill of the parameter

– If shows statistical skill then the forecast parameter can be useful to future

forecasts

Objective Verification

15 Heavy Rain Cases / Missouri, Kansas, Oklahoma / 2014-15

EPEC calculated with Rapid Refresh (RAP) grid initial fields

Precipitation data

– NCEP/EMC 4 km Gridded data (GRIB) Stage IV data

– 4-km precip data interpolated to RAP grids

Comparison of EPEC to accumulated precipitation for ensuing 6-hours

– Correlations, POD, FAR, CSI, bias

Correlations

– All EPEC values to precip

accumulation values >12.7mm

in 6 hours

POD, FAR, CSI, Bias

– EPEC values > 74 to precip

accumulation values >12.7mm

in 6 hours

Tested against climatology

One standard deviation above mean

for day to day EPEC

BELOW

One standard deviation below mean for EPEC

on days w/elevated convection & heavy rainfall

AcknowledgementsThis work is supported in part by the United States National Science Foundation (NSF), Awards AGS-1258358 and IIA-1355406. Any opinions, findings, conclusions or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of NSF.

• Strong signal;

strong variability

• Strong signal;

small variability

PWAT KINX

McCoy (2014) composites found strong signals

and low variability in a few key parameters

What is EPEC?

EPEC = KINX + PWAT + (Div250 x 100,000)

mm s-1

Units are neglected

Originally estimated from mean and interquartile range plots from McCoy (2014)

EPEC reference values developed directly from soundings in the EAX county warning area yielded similar results

EPEC reference values (estimated from McCoy 2014)