Rip Currents--Killer Currents Jim Lushine

Outline of Presentation•Rip Current Fatalities

•Data

•Forecasting

•Verification

•NWS Products

•Future Work

Rip Current Fatalities

Southeast Florida Rip Current Fatalities

0

5

10

15

20

25

1979-2003

Florida Rip Current Fatalities

0

10

20

30

40

1989-2003

Florida Weather-related Fatalities1989-2003

278

134

63

24

0

50

100

150

200

250

300

Rip Current Lightning Tornado Hurricane

Dea

ths

United States Rip Current Fatalities

50

41 43

0

10

20

30

40

50

Fatalities

2001 2002 2003

Years

Storm Data

Weather-related Formation Factors1. Local Gradient Wind2. Swell

Non-Weather-related Formation Factors•Time of Low Tide*

•Persistence•Tidal Currents

•Deep Water Currents (e.g. Gulf Stream)

•Seismological Factors

•*SE Florida Coast

Data

Florida Marine Observations

Four Factors in Forecasting Rip Currents

Wind Factor

Gradient Wind vs Rip Current Fatalities along SE Florida Coast

05

101520253035404550

% of Time

11 12 13 14 15 16

Average Wind Speed

northeasteast northeasteasteast southeastsoutheastsouth southeast

Gradient Wind vs Non-Rip Current Fatalities along SE

Florida Coast

0

5

10

15

20

25

30

% of TIme

4 5 6 7 8 9 10 11

Avg Wind Speed

NNEESESSWWNW

Sea Breeze Effect

Convective Wind Initiation

Swell Factor

Swell Height* vs Rip Currents

• <2 Feet---No effect on rip currents

• 2-7 Feet---Mdt Risk of rip currents

• >7 Feet---High Risk of rip currents

• *Swell Period also important

Tidal Factor

Faster Rip Current near Low Tide

Tidal Variation of Fatalities

02468

10121416

No. of Fatalities

Hito1

1to2

2to3

3to4

4to5

5toLo

Loto1

1to2

2to3

3to4

4to5

5toHi

Tidal Times

1979-1988

Weaker Swimmers Can go Farther Offshore?

PersistenceFactor

Days Between Initiation of Rip Currents and the First Fatality

6

19

31

37 3943

48

05

101520253035404550

Cumulative No. of

Drownings

1 2 3 4 5 6 7

Days

Gradient Winds vs Residual Rip Current Fatalities in SE Florida

0

10

20

30

40

50

60

% of Time

7 8 9 10

Avg Wind Speed

NNEESESSWWNW

Beach Patrol Rescue Reports

Daily Rip Current Risk1=Low2=Moderate3=High

Verification

0.92

0.570.62

0.58

0.370.32

0

0.10.2

0.30.4

0.50.6

0.70.8

0.91

POD FAR CSI

Rip CurrentSevere Weather

NWS Rip Current-Related Products

• Surf Forecast

• Hazardous Weather Outlook

• Marine Weather Statement

• Zone Forecasts (Headlines)

Decision to Include in ZFP

• Weekday vs Weekend/Holiday

• Improving Weather from yesterday

• Change in surf conditions from yesterday

• Low Tide in the afternoon

Future Work

Tidal Variation of Fatalities= Hourly Rip Current Risk?

02468

101214

Fatalities

Hito1

1to2

2to3

3to4

4to5

5toLo

Loto1

1to2

2to3

3to4

4to5

5toHi

Tidal Times

1994-2003

Beach Geomorphology

• Renourishment

• Type of Sand

• Persistence of Rip Channels

Upcoming Rip Current Events

• Technical Workshop (April 6-7, 2004)

• NWS Media Event (May 24, 2004)

• FACVB meeting (June 10, 2004)

• COMET Module (Summer 2004)

Florida’s Uniform Flag Warning System

The End