Analysis of the Analysis of the 10 July 200210 July 2002

St. Cloud, Minnesota St. Cloud, Minnesota Flash Flood EventFlash Flood Event

Justin TurcotteJustin Turcotte5 April 20035 April 2003

Images of the FloodImages of the Flood

Images from St. Cloud Times, 11 July 2002

What Happened?What Happened?

Significant amount of Significant amount of rain in a very short rain in a very short amount of timeamount of time

Rain fell on already Rain fell on already saturated groundsaturated ground

SCSU (near STC): SCSU (near STC): 4.29”, 2.70” within 1hr 4.29”, 2.70” within 1hr 45 min45 min

AXN: 3.52”, Inch an AXN: 3.52”, Inch an hour for three hourshour for three hours

From St. Cloud Times 2002

Month’s Worth of Rain in One DayMonth’s Worth of Rain in One Day

The St. Cloud area The St. Cloud area average July average July precipitation is 3.38”precipitation is 3.38”

Event followed above Event followed above average June average June precipitationprecipitation

Saturated soilSaturated soil

METAR from Alexandria, MNMETAR from Alexandria, MN

KAXN 100853Z AUTO 08017G25KT KAXN 100853Z AUTO 08017G25KT 3/4SM3/4SM +TSRA+TSRA BR BKN007 BR BKN007 OVC019 19/19 A3000 RMK AO2 PK WND 09026/0817 LTG DSNT OVC019 19/19 A3000 RMK AO2 PK WND 09026/0817 LTG DSNT ALQDS TSE0757B05 SLP153 ALQDS TSE0757B05 SLP153 P0093P0093 60104 T01940194 56021 60104 T01940194 56021

KAXN 100953Z AUTO 09013G21KT KAXN 100953Z AUTO 09013G21KT 1 1/4SM1 1/4SM +TSRA+TSRA BR OVC007 BR OVC007 19/18 A3000 RMK AO2 LTG DSNT ALQDS SLP151 19/18 A3000 RMK AO2 LTG DSNT ALQDS SLP151 P0119P0119 T01890183T01890183

KAXN 101053Z AUTO 10016G23KT 10SM BKN033 BKN060 KAXN 101053Z AUTO 10016G23KT 10SM BKN033 BKN060 OVC100 19/18 A2999 RMK AO2 PK WND 10029/1032 LTG DSNT OVC100 19/18 A2999 RMK AO2 PK WND 10029/1032 LTG DSNT E TSE38RAE44 SLP149 E TSE38RAE44 SLP149 P0098P0098 T01890178 T01890178

Soil Conditions June/JulySoil Conditions June/July

Images from National Climatic Data Center (NCDC)

The K-IndexThe K-Index

KIKI = (T850mb- T500mb) + Td850mb -(T700mb -= (T850mb- T500mb) + Td850mb -(T700mb -Td700mb). Td700mb).

0-15 0-15 No thunderstormsNo thunderstorms 18-19 18-19 Thunderstorms unlikelyThunderstorms unlikely 20-25 20-25 Isolated thunderstormsIsolated thunderstorms 26-30 26-30 Widely scattered thunderstormsWidely scattered thunderstorms 30-35 30-35 Numerous thunderstormsNumerous thunderstorms 36-39 36-39 Thunderstorms very likelyThunderstorms very likely 40+ 40+ 100% chance of thunderstorms100% chance of thunderstorms MPX 1200z Sounding MPX 1200z Sounding K = 38 K = 38 (bet the farm!)(bet the farm!)

from Sturtevant 1995

Type “F”: Northwest Flow Ridge RidersType “F”: Northwest Flow Ridge Riders

                                                                                                      

http://locust.mmm.ucahttp://locust.mmm.ucar.edu/case-selection/r.edu/case-selection/

SurfaceSurface RadarRadar SatelliteSatellite

Mosquito Breeding GroundMosquito Breeding GroundLand of 10,000++ LakesLand of 10,000++ Lakes

from St. Cloud Times 2002

Storm ReportsStorm ReportsJuly 9 - 10July 9 - 10

SummarySummary

Abundant moisture throughout atmosphereAbundant moisture throughout atmosphere Moisture convergence over areaMoisture convergence over area Strong 500 hPa vorticity advectionStrong 500 hPa vorticity advection Upper-air divergenceUpper-air divergence Slow moving stormsSlow moving storms Extreme intensity rainfall ratesExtreme intensity rainfall rates Saturated groundSaturated ground FLOODFLOOD

Why did the lady go out doors with her Why did the lady go out doors with her purse open? Because she expected purse open? Because she expected some change in the weather.some change in the weather.

http://www.kvue.com/weather/kids/funandgames/jokes.html