WFO Binghamton Maddox Synoptic Type Flash Flood

Classification Study

By Christopher GitroNWS Binghamton, NY

Flash flooding remains the number 1 weather killer across the US

29 flash flood related fatalities in BGM’s CWA since Jan 1996 ◦ Most Recent: 01 Oct 10

Knowledge of favorable synoptic patterns responsible for significant flash flooding → higher situational awareness →Pattern Recognition

First local attempt to classify large scale flash flood episodes based on large scale synoptic patterns

Motivation

Main Goal: Classify historically significant past flash flood episodes by the Maddox Synoptic classification scheme

Flash flood events from the winter of 1996 through present were examined ◦ 42 total Events

An event was classified if any of the following three occurred: 1) 5 or more flash flood reports from a single event 2) $500K crop/property damage 3) Fatality(ies) occurred

For synoptic environments in which the synoptic pattern did not reflect the traditional patterns as described by Maddox et al. (1979), the events were labeled as “Unclassified”

If a flash flood event resulted from a remnant tropical circulation moving across the area, the event was classified as “Tropical”

Methodology

Archived H50 (SPC, HPC) 00Z/12Z Maps

Archived HPC analyzed surface maps

Radar animations analyzed through GR Analyst

NAM BUFKIT Proximity Soundings◦ Sounding was selected by

picking the hour from closest NAM forecast point to time of initial flash flood report

◦ (LLJ winds (BUFKIT defined), Cloud Layer Winds, MBE Speeds, Warm Cloud Depth, etc)

Anomaly departures derived from NCEP/NCAR Reanalysis data

Methodology Cont.

Review

Synoptic Frontal

Meso High All images from Maddox et al. (1979)

Results

Frontal Synoptic Meso High Unclassified Tropical

0

5

10

15

20

25

7

20

2

10

3

Flash Flood Event Classifi-cation

Frontal, 16.67%

Synoptic 47.62%

Unclassi-fied23.81

%

Meso High, 4.76%

Tropical, 7.14%

Flash Flood Synoptic Type by Percentage

Frontal

Synoptic

Unclassified

Meso High

Tropical

42 Total Events

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

1

2

3

4

5

6

7

3

0

3

2

3

6

7 7

5

0

3 3

Events by Month

Frontal Synoptic Meso High Unclassified Tropical0

1

2

3

4

5

6

7

8

Type by Season

WinterSpringSummerFall

Frontal Synoptic Unclassified Meso High Tropical0

10

20

30

40

50

60

70

80

LLJ Wind Speeds (kts)

Q1MinMedianMaxQ3

0

10

20

30

40

50

60

70

80

LLJ Winds (kts) - All Events

Q1MinMedianMaxQ3

Frontal Synoptic Unclassified Meso High Tropical0

10

20

30

40

50

60

MBE Speed (kts)

Q1MinMedianMaxQ3

Frontal Synoptic Unclassifed Meso High Tropical0

50

100

150

200

250

300

350

400

450

500

PWAT vs Climo (% of normal)

Q1MinMedianMaxQ3

Frontal Synoptic Unclassified Meso High Tropical0

2000

4000

6000

8000

10000

12000

14000

16000

Warm Cloud Layer Depth (ft)

Q1MinMedianMaxQ3

Frontal Type Anomaly Departures

H50 Height (m)

PWAT

MSLP

H85 Meridional Winds

Sfc Air Temp

Synoptic Type Anomaly Departures

H50 Height (m) MSLP

H85 Meridional Winds

Sfc Air Temp

PWAT

Meso High Anomaly Departures

H50 Height (m) MSLP

H85 Meridional Winds

Sfc Air Temp

PWAT

Tropical Anomaly Departures

H50 Height (m) MSLP

H85 Meridional Winds

Sfc Air Temp

PWAT

1200 UTC 28 May 2002 SPC H50 Analysis (NAM)

1500 UTC 28 May 2002 HPC Analyzed SFC Analysis

Frontal Type ExampleBear Creek, PA (28 May 02)

Frontal Type ExampleBear Creek, PA Flash Flood (28

May 02)

• $5 Million Property Damage

1200 UTC 25 Jan 2010 SPC H50 Analysis (NAM)

Synoptic Type Example25 Jan10 Flash Flood

1500 UTC 25 Jan 2010 HPC Analyzed SFC Analysis

Synoptic Type Example25 Jan 10

Meso High ExampleColchester, NY Flash Flood

1200 UTC 19 June 2007 NCEP H50 Analysis

2100 UTC 19 June 2007 HPC Analyzed SFC Analysis

Meso High ExampleColchester, NY Flash Flood (19 Jun 07)

• $30 Million Property Damage• 4 Fatalities

The BGM HSA is susceptible to all 3 eastern US Maddox Flash Flood types

Synoptic type flash flood producing environments most common (20 cases)

Not all synoptic patterns cleanly fit into the Maddox classification scheme (10 unclassified, 3 tropical)

Frontal/Meso High less common but potentially devastating considering BGM’s highly variable terrain (terrain anchoring)◦ Both Meso High cases had fatalities

Conclusions

Synoptic flash flood producing environments showed the most variable spread (LLJ, Cloud Layer Winds, MBE Speeds)

Weaker forced frontal/meso high environments displayed less variable spread ◦ Smaller sample size

The use of anomaly departure information can heighten a forecaster’s SA of a potential high impact flash flood producing environment 24-48 hrs out

Conclusions cont.

ReferencesMaddox, R. A., C. F. Chappell and L. R. Hoxit, 1979: Synoptic and meso-α scale aspects of flash flood events. Bull. Amer. Meteor. Soc., 60, 115-123.