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Organization and Atmospheric Conditions of Flash Floods in the Northeastern United States. Stephen M. Jessup Dept. of Earth and Atmospheric Sciences Cornell University. Research Question.

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Organization and Atmospheric Conditions of Flash Floods in the Northeastern United States

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Organization and atmospheric conditions of flash floods in the northeastern united states

Organization and Atmospheric Conditions of Flash Floods in the Northeastern United States

Stephen M. Jessup

Dept. of Earth and Atmospheric Sciences

Cornell University


Research question

Research Question

Are flash-flood-producing precipitation events in the northeastern U.S. different from those in other regions of the country?


Organization and atmospheric conditions of flash floods in the northeastern united states

Other Regions

N = 168

Northeast

N = 16

Schumacher and Johnson, 2006 (SJ2006)


Methodology

Methodology

Select events: UseStorm Data reports to select a pool of events and use precipitation amounts to select the Storm Data report from each event day to include.

Estimate precipitation: ConvertNEXRAD radar data to basin-averaged rainfall estimates using AMBER (the same real-time basin-averaged rainfall accumulation estimation algorithm used by the NWS).

Classify events: Expand upon the classification system of Schumacher and Johnson (2006).

Describe environmental conditions: Generatecomposite maps from the North American Regional Analysis.


Overview

Overview

  • Motivation

  • Research Question

  • Methodology

  • Event classification

  • Precipitation Estimates

  • Atmospheric Conditions

  • Summary


Organization and atmospheric conditions of flash floods in the northeastern united states

Flash Floods, Northeast, This Study

Events meeting SJ2006 Threshold (N = 23)

All Events (N=187)

Extreme Precipitation Events, SJ2006

Other Regions (N = 168)

Northeast (N=13)


Organization and atmospheric conditions of flash floods in the northeastern united states

Linear Events

Synoptic Events

Other Events

Back-building Events

Multiple Events


Organization and atmospheric conditions of flash floods in the northeastern united states

Linear Events

Scalar Events

Back-building Events

Scattered Events


Organization and atmospheric conditions of flash floods in the northeastern united states

Linear Events

TLAS

Parker and Johnson, 2000

SJ2006


Organization and atmospheric conditions of flash floods in the northeastern united states

Scale

Events

Synoptic

SYN

Large Mesoscale

LM

24 hr

150 km

Medium Mesoscale

MM

50 km

Small Mesoscale - Isolated

SMISO


Organization and atmospheric conditions of flash floods in the northeastern united states

Back-building Events

Merging

Back-building

BBMERGE

t0

t0+Δt

Back-building Followed by

Linear Features (BBMULT1)

Linear Features Followed by

Back-building (BBMULT2)

t0

t0

t0+Δt

t0+Δt


Organization and atmospheric conditions of flash floods in the northeastern united states

Scattered Events

Scattered Precipitation

Training SCTTR

ScatteredPrecipitation

“Random” Motion

SCTRAND

Scattered

Precipitation

Merging Features

SCTMERGE

Scattered

Precipitation

Small Mesoscale

SCTSM


Event classification distribution

Event Classification Distribution


Overview1

Overview

  • Motivation

  • Research Question

  • Methodology

  • Event classification

  • Precipitation Estimates

  • Atmospheric Conditions

  • Summary


Precipitation analysis

Precipitation Analysis

Do certain types of organization tend to produce significantly more (or less) precipitation?


Organization and atmospheric conditions of flash floods in the northeastern united states

Precipitation Analysis

Do certain types of organization tend to produce more precipitation during certain times of day or certain times of year?


Overview2

Overview

  • Motivation

  • Research Question

  • Methodology

  • Event classification

  • Precipitation Estimates

  • Atmospheric Conditions

  • Summary


Environmental properties of storm types

Environmental Propertiesof Storm Types

Are there detectable differences in the synoptic

and mesoscale environments of different types of events?


Organization and atmospheric conditions of flash floods in the northeastern united states

SYN

LM

MM

SMISO


Organization and atmospheric conditions of flash floods in the northeastern united states

Back-building Events

BB

BBMERGE

BBMULT1

BBMULT2


Scattered events

Scattered Events

SCTTR

SCTRAND

SCTMERGE

SMSCT


Overview3

Overview

  • Motivation

  • Research Question

  • Methodology

  • A look at flash flood reports

  • Event classification

  • Precipitation Estimates

  • Atmospheric Conditions

  • Summary


Which types of events produce the most rainfall the most often

Which types of events produce the most rainfall the most often?


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

LS

TLAS

MM

SMISO

BB

BBMERGE

SCTTR

SCTRAND

SCTSM

BBMULT1

BBMULT2

SCTMERGE


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

>150 km

>150 km

>24 hr

<24 hr

LS

TLAS

MM

SMISO

50-150 km

<50 km

BB

BBMERGE

SCTTR

SCTRAND

BB

BB

BBMULT1

BBMULT2

SCTMERGE

SCTSM

BB

BB


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

>150 km

>150 km

>24 hr

<24 hr

LS

TLAS

MM

SMISO

50-100 km

<50 km

BB

BBMERGE

SCTTR

SCTRAND

BBMULT1

BBMULT2

SCTMERGE

SCTSM


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

>150 km

>150 km

>24 hr

<24 hr

LS

TLAS

MM

SMISO

50-100 km

<50 km

BB

BBMERGE

SCTTR

SCTRAND

BBMULT1

BBMULT2

SCTMERGE

SCTSM


Which types of events occur in the most favorable environments

Which types of events occur in the most “favorable” environments?

  • Dynamics


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

LS

TLAS

MM

SMISO

BB

BBMERGE

SCTTR

SCTRAND

BBMULT1

BBMULT2

SCTMERGE

SCTSM


Which types of events occur in the most favorable environments1

Which types of events occur in the most “favorable” environments?

  • Dynamics

  • Slow winds


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

LS

TLAS

MM

SMISO

BB

BBMERGE

SCTTR

SCTRAND

BBMULT1

BBMULT2

SCTMERGE

SCTSM


Which types of events occur in the most favorable environments2

Which types of events occur in the most “favorable” environments?

  • Dynamics

  • Slow winds

  • High moisture


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

LS

TLAS

MM

SMISO

BB

BBMERGE

SCTTR

SCTRAND

BBMULT1

BBMULT2

SCTMERGE

SCTSM


How do high precipitation events differ from low precipitation events

How do high precipitation events differ from low precipitation events?

  • Dynamics - red

  • Low-level Winds - yellow

  • Mid-level Moisture – blue

  • Small sample size – black

  • No difference - white


Organization and atmospheric conditions of flash floods in the northeastern united states

TS

PS

SYN

LM

LS

TLAS

MM

SMISO

BB

BBMERGE

SCTTR

SCTRAND

BBMULT1

BBMULT2

SCTMERGE

SCTSM


Organization and atmospheric conditions of flash floods in the northeastern united states

Are flash-flood-producing precipitation events in the northeastern U.S. different from those in other regions of the country?

Yes…

They appear to be more disorganized.


Organization and atmospheric conditions of flash floods in the northeastern united states

Are flash-flood-producing precipitation events in the northeastern U.S. different from those in other regions of the country?

No…

They still get the job done.


Future work

Future Work

  • Frequency of storm types in other regions

  • Objective analysis of storm types via computer algorithm

  • Characteristics of flash floods that produce fatalities and significant damage

  • Computer modeling of BBMERGE, SCTRAND, and SCTMERGE events

  • Linking precipitation organization and hydrology

    • Role of antecedent moisture

    • How does storm type relate to the spatial characteristics of watershed response?


Organization and atmospheric conditions of flash floods in the northeastern united states

Acknowledgments

This work is supported by

NSF grant EAR 0911076.

Special thanks to my Ph.D. advisor,

Steve Colucci

Many thanks to many friends and colleagues.

Thank you!


Organization and atmospheric conditions of flash floods in the northeastern united states

Why is a taxonomy of warm season rainfall important?

  • Provides a research framework for anticipating and observing rainfall organization

    • Some types of organization produce more rainfall, or produce more widespread heavy rainfall than others.

    • While, especially in the central U.S., MCSs are important heavy rain makers, more disorganized (or larger and more uniform) rainfall can also produce significant flash flooding, especially, it seems, in the northeast U.S.

    • The spatial properties of precipitation undoubtedly play a role in dictating the hydrologic response .

  • Provides another layer of flash flood forecaster awareness

    • Anticipation of rainfall organization based on atmospheric conditions.

    • Real-time radar recognition of rainfall organization and related flood potential.


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