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)