# Presentation: 352583

## Flash Flood Case Study : June 24, 2006 

- Ray Kruzdlo
- Severe Weather Warning Technology Workshop
- Stories From the Field
- Norman, Oklahoma
- July 10-12, 2007

## Synoptic Setup (18z/24)

## Synoptic Setup (12z/24)

## Synoptic Setup (18z/24)

## Synoptic Setup (00z/25)

## Regional Radar (19z/24)

## Regional Radar (23z/24)

## RFC 1 Hr Flash Flood Guidance

- Monmouth Co 2.27”

- Burlington Co 2.94”
- Camden Co 2.94”
- Gloucester Co 3.06”

- Chester Co 2.27”

- Bucks Co    1.88”
- Montgomery Co  2.51”

## KDIX STP (2258z)

- Mainly 1 inch or less with embedded  areas of 1 to 3 inches.

## KDOX STP (2256z)

- Mainly 1 to 2.5 inches with embedded areas 3 to 4 inches.

## FFMP : FFG and the 80% Rule

- Chester Co
- 1 Hr FFG hit 80% at 1902z
- Event verified at 1930z
- 28 minute LT

- 1.89/2.28=82.8%

## Monmouth County, NJ

- Warning issued at 2021z
- 2026z image
- Ratio = 32%

- 1.15/3.11=36.9%

## Monmouth County, NJ

- Event verified  at 2200z
- 2159z Image
- Ratio = 34%
- Highest ratio during event = 47% at 2047z

## Storm Data Entry

- Poor drainage, street, and small creek flooding was reported especially across the southern portion of the county.

## Gloucester County, NJ 

- Warning issued at 2217z
- 2216z image
- Ratio = 45%

- Numbers don’t add up

## Gloucester County, NJ

- Event verified  at 2220z
- 2220z Image
- Ratio = 51%
- Highest ratio during event = 67% at 2237z

- Ratio and Diff don’t add up
- 1.54/2.48=62%

## Camden County, NJ

- Warning issued at 2217z
- 2216z image
- Ratio = 55%

- 1.76/2.95=59.6%

## Camden County, NJ

- Event verified  at 2235z
- 2233z Image
- Ratio = 55%
- Highest ratio during event = 59% at 2224z

- Numbers add up, but not elsewhere

## Burlington County, NJ

- Warning issued at 2217z
- 2216z image
- Ratio = 24%

- .78/1.89=41.2%

## Burlington County, NJ

- Event verified  at 2300z
- 2258z Image
- Ratio = 40%
- Highest ratio during event = 42% at 2241z

- 1.32/1.89=69.8%

## Storm Data Entries

- Thunderstorms with heavy rain caused flooding of roadways and small streams from central Gloucester County northeast through central portions of Burlington County. In Gloucester County, several roads were closed in and around Pitman with up to three feet of water on them. Roadway closures in Burlington County occurred in Burlington, Pemberton, and Southampton Townships. Measured storm totals included 4.20 in Glassboro (Gloucester County), 2.89 inches in Medford (Burlington County) and 2.59 inches in Wrightstown (Burlington County).

## Hydrologic Warning Shortcomings 

- Urbanization - Urban flash flooding 15 to 30 minutes
- Types of precipitation - Warm rain processes
- Radar issues - Blockage, distance, Z-R relationship, FFMP
- Using multiple radars – one too high, the other too low
- FFMP – Reliance on radar and FFG, inconsistent values
- In this example, using only a method related to FFMP would have led to more missed events or events with zero lead time. The 80% rule did not work well. Was it because FFG was too high or STP inaccurate?

## Addressing the Shortcomings

- _Unrelated to FFMP_
- Understand meteorological event
- _Questions related to FFMP_
- Should FFG be issued more than 4 times a day when necessary?
- Could FFG be partially automated and recalibrated during an event? Hourly basis?
- Could observation data be ingested to supplement and/or correct radar based data?
- Can radar based data be improved? (dual pol and hail)