The Extreme East-Central Missouri  Flash Flood of 6-7 May 2000
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The Extreme East-Central Missouri Flash Flood of 6-7 May 2000 James T. Moore, John P. Gagan Cooperative Institute for Precipitation Systems Department of Earth and Atmospheric Sciences Saint Louis University and Fred H. Glass NWSFO St. Charles, MO.

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The Extreme East-Central Missouri Flash Flood of 6-7 May 2000

James T. Moore, John P. Gagan

Cooperative Institute for Precipitation Systems

Department of Earth and Atmospheric Sciences

Saint Louis University

and Fred H. Glass

NWSFO St. Charles, MO

Hydrometeorology Course for RFC/HPCFriday, 8 December 2000


Extreme heavy rain in franklin county missouri
Extreme Heavy Rain in Franklin County, Missouri 2000

  • Occurred during the nighttime and early hours of 6-7 May 2000

  • Rainfall exceeding 4 inches (100 mm) fell over a 5500 km2 area, with embedded amounts over 12 inches (300 mm)

  • There were two fatalities and property damage of over 100 million dollars

  • 379 structures damaged or destroyed in Franklin County; declared a disaster area by the President

  • Flat Creek in Franklin County rose about 15 feet (4.57 m) destroying two mobile home parks.



Infrared Satellite Imagery Valid 1815 UTC 5 May 2000 to 1815 UTC 6 May 2000


NIDS Radar Imagery Valid 0134 to 1800 UTC 6 May 2000 http://www.rap.ucar.edu/staff/pneilley/NIDS_archives.html


24-Hour Precipitation Analysis for the Period Ending 1200 UTC 7 May 2000


Accumulated Rainfall ( Period Ending 1200 UTC 7 May 2000Grey) 30 Minute Rainfall (Blue)


GOES-8 Infrared Satellite Loop Valid 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000


  • Pre-storm Environment 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

  • Weakening mid-level cyclonic vortex (MCV) with warm core characteristics moving northeasterly from northeast Oklahoma into central Missouri.

  • Very moist tropospheric conditions:

    • 1000-500 mb mean relative humidity values > 80%

    • Lower tropospheric dewpoints in lower-middle teens ºC

    • PWs of 1.19 - 1.47 inches (153-216%)

    • warm cloud depths ranged from 3.1 –3.3 km

  • Weak instability with CAPEs between 500-1000 J kg-1

  • Weak vertical wind shear in the mid-upper levels

  • Strong Low-Level Jet (LLJ) from the south-southwest (at times exceeding 50 knots)


925 mb surface 7 May 2000 00 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

---- Isodrosotherms


925 mb surface 7 May 2000 12 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

---- Isodrosotherms


850 mb surface 7 May 2000 00 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

--- Isotachs


850 mb surface 7 May 2000 12 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

--- Isotachs


500 mb surface 7 May 2000 00 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

--- Isotherms


500 mb surface 7 May 2000 12 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

--- Isotherms


250 mb surface 7 May 2000 00 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

--- Isotachs


250 mb surface 7 May 2000 12 UTC 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

--- Isotachs


  • THE EVENT 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

  • A mesoscale convective system (MCS) formed near the center of the MCV and created an outflow boundary at the surface

  • This outflow boundary was weak, due to the very moist atmosphere in which it formed, and moved very little during the nighttime hours of 7 May 2000

  • The southwesterly LLJ was strong and wide. It flowed nearly perpendicular to the outflow boundary, veering as time progressed, and acted as a focusing mechanism for convection


  • THE EVENT (cont.) 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

  • The steering flow (from 700 mb to 300 mb) was predominantly westerly, veering as time progressed, and was oriented parallel to the outflow boundary

  • The nature of the training changed with time from west-east to northwest-southeast in concert with a change in cell motion

  • This change in cell motion was related to veering of the cloud-layer wind


Surface Analysis Valid 00 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

14

15

13

16

17

11

10

18

10

11

11

12

17

12

13

14

15

16

18


Surface Analysis Valid 04 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000


Surface Analysis Valid 06 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000


Surface 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000efor 06 UTC 7 May 2000


Surface Analysis Valid 08 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000


Surface 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000efor 08 UTC 7 May 2000


Surface Analysis Valid 10 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000


Surface 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000efor 10 UTC 7 May 2000


RUC Initialization Composite Chart Valid 12 UTC 6 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

Precipitable Water (1.2 inches) 1000-500mb Mean RH (%)

K-Index(28)


RUC Initialization Composite Chart Valid 00 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

Precipitable Water (1.2 inches) 1000-500mb Mean RH (%)

K-Index(28)


RUC Initialization Composite Chart Valid 12 UTC 7 May 2000 1815 UTC 6 May 2000 to 1815 UTC 7 May 2000

Precipitable Water (1.3 inches) 1000-500mb Mean RH (%)

K-Index(28)




Lincoln, IL (ILX) Skew-T Valid 00 UTC 7 May 2000

wcd = 3.0 km


Lincoln, IL (ILX) Skew-T Valid 12 UTC 7 May 2000

wcd = 3.31 km


RUC Initialization 950 mb to 850 mb Layer-Averaged Wind Vectors and Isotachs Valid 00 UTC 7 May 2000


RUC Initialization 950 mb to 850 mb Layer-Averaged Wind Vectors and Isotachs Valid 03 UTC 7 May 2000


RUC Initialization 950 mb to 850 mb Layer-Averaged Wind Vectors and Isotachs Valid 06 UTC 7 May 2000


RUC Initialization 950 mb to 850 mb Layer-Averaged Wind Vectors and Isotachs Valid 09 UTC 7 May 2000


RUC Initialization 950 mb to 850 mb Layer-Averaged Wind Vectors and Isotachs Valid 12 UTC 7 May 2000


Vertical Wind Profile Display from the KLSX WSR-88D Valid 0600 UTC to 0700 UTC 7 May 2000


Vertical Wind Profile Display from the KLSX WSR-88D Valid 0700 UTC to 0800 UTC 7 May 2000


Vertical Wind Profile Display from the KLSX WSR-88D Valid 0800 UTC to 0900 UTC 7 May 2000


Vertical Wind Profile Display from the KLSX WSR-88D Valid 0900 UTC to 1000 UTC 7 May 2000


Vertical Wind Profile Display from the KLSX WSR-88D Valid 1000 UTC to 1100 UTC 7 May 2000


Loop of one-hour KLSX WSR-88D rainfall estimation for the time period 04 UTC to 11 UTC 7 May 2000



KLSX WSR-88D plane view of the cross-section of reflectivity (dBZ) from 0415 UTC to 0831 UTC 7 May 2000

B

A


KLSX WSR-88D Cross-Section Valid 0415 UTC to 0831 UTC 7 May 2000

A

B


KLSX WSR-88D plane view of the cross-section of reflectivity (dBZ) from 0730 UTC to 1100 UTC 7 May 2000

A

B

B


KLSX WSR-88D Cross-Section Valid 0731 UTC to 1100 UTC 7 May 2000

A

B


KLSX WSR-88D Reflectivity Loop (dBZ) Valid 0415 UTC to 1100 UTC 7 May 2000



  • Diagnostic View of the Propagation Vectors UTC 7 May 2000

  • Prognostic storm-motion vectors are calculated using the LLJ and mean 850-300 mb wind vectors (Corfidi 1996)

  • In this case, the prognostic vectors that were calculated gave an erroneous system-motion speed and direction because they relied solely on the LLJ

  • “True” propagation vectors were calculated using the satellite-derived system motion and radar-derived cell motion vectors to obtain the actual nature of the propagation

  • The finding that propagation is influenced by more than the LLJ is consistent with earlier work by Moore et al. (1993) and Corfidi (1998)

  • In this case, propagation appeared to be influenced by the outflow boundary, mesolow, and the LLJ






Propagation Vector Loop Valid 05 UTC to 11 UTC 7 May 2000


How did the numerical models do

How did the numerical models do? Valid 05 UTC to 11 UTC 7 May 2000

We take a look at the 00 UTC run of the Eta for 7 May 2000


Eta-40 km 00 UTC 7 May 2000 Run QPF 00-06 Valid 05 UTC to 11 UTC 7 May 2000UTC 7 May 2000


Eta-40 km 00 UTC 7 May 2000 Run QPF 06-12 Valid 05 UTC to 11 UTC 7 May 2000UTC 7 May 2000


Eta-40 km 00 UTC 7 May 2000 Run QPF 12-18 Valid 05 UTC to 11 UTC 7 May 2000UTC 7 May 2000


  • CONCLUSIONS Valid 05 UTC to 11 UTC 7 May 2000

  • The heavy rain event that occurred during the nighttime hours of 7 May 2000 was due to regenerative convection which resulted in a quasi-stationary MCS

  • Franklin County, MO was deluged with over 10 inches of rain in a six-hour period, with some portions of the county receiving 14-16 inches

  • Catastrophic flooding occurred along Flat Creek watershed which runs through the center of Union in Franklin County. Damage estimates exceeded $100 million.


  • CONCLUSIONS (cont.) Valid 05 UTC to 11 UTC 7 May 2000

  • The heavy rainfall event in MO was part of a cyclic heavy rainfall system associated with a mid-level, warm core vortex that developed from a cold core low.

  • As the convective system grew, a weak outflow boundary became aligned parallel to the upper-level flow and nearly normal to the LLJ

  • As the MCS matured, a weak surface mesolow formed upstream from the convection, further enhancing low-level convergence

  • Diagnostic calculations of the propagation vector revealed that the storm motion remained < 3.5 m s-1


  • CONCLUSIONS (cont.) Valid 05 UTC to 11 UTC 7 May 2000

  • Vector analysis further reveals that the propagation vector was opposite to the cell motion vector signaling a quasi-stationary MCS

  • The Corfidi Vector Method was inappropriate in this case as the storm-relative inflow was NOT solely a function of the LLJ

  • The heavy rain environment was characterized by:

    • weak mid-upper level wind shear

    • high mean surface-500 mb RH

    • deep warm cloud depths (~3.3 km)

    • PW values > 175% of normal (> 1.3 inches)

    • modest CAPE values (500-1000 J kg-1)


Conclusions cont
CONCLUSIONS (cont.) Valid 05 UTC to 11 UTC 7 May 2000

  • High e air (> 340 K) resided to the southwest of the MCS

  • The MCS formed downstream from a maxima in the 850 mb moisture transport vectors

  • The various Eta model QPFs were on the order on 0.5 inches for the 18 h period.

  • One would not expect numerical models to be able to handle this meso- scale heavy rain event – especially a hydrostatic model with an inability to simulate downdrafts (albeit weak ones)


This presentation can be viewed and/or downloaded at the following web site:

http://www.eas.slu.edu/CIPS/Presentations

In addition, Fred Glass of the NWSFO in St. Charles, MO has written a preprint for the 81st Annual AMS meeting. To obtain a copy of this preprint email Fred at:

[email protected]


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