Flash Flood Case Study : June 24, 2006Flash 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 (18z/24)

Synoptic Setup (12z/24)Synoptic Setup (12z/24)

Synoptic Setup (18z/24)Synoptic Setup (18z/24)

Synoptic Setup (00z/25)Synoptic Setup (00z/25)

Regional Radar (19z/24)Regional Radar (19z/24)

Regional Radar (23z/24)Regional Radar (23z/24)

KDIX STP (2258z)KDIX STP (2258z)

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

KDOX STP (2256z)KDOX STP (2256z)

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

FFMP : FFG and the 80% RuleFFMP : 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, NJMonmouth County, NJ

Warning issued at 2021z

2026z image

Ratio = 32%

1.15/3.11=36.9%

Monmouth County, NJMonmouth County, NJ

Event verified at 2200z

2159z Image

Ratio = 34%

Highest ratio during event = 47% at 2047z

Storm Data EntryStorm Data Entry

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

Gloucester County, NJ Gloucester County, NJ

Warning issued at 2217z

2216z image

Ratio = 45%

Numbers don’t add up

Gloucester County, NJGloucester 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, NJCamden County, NJ

Warning issued at 2217z

2216z image

Ratio = 55%

1.76/2.95=59.6%

Camden County, NJCamden 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, NJBurlington County, NJ

Warning issued at 2217z

2216z image

Ratio = 24%.78/1.89=41.2%

Burlington County, NJBurlington 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 EntriesStorm 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 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 ShortcomingsAddressing 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)