Post on 08-Feb-2016
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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
05
10152025
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 2003Years
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 16Average 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 11Avg 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
3137 39
4348
05
101520253035404550
Cumulative No. of
Drownings
1 2 3 4 5 6 7Days
Gradient Winds vs Residual Rip Current Fatalities in SE Florida
0
10
20
30
40
50
60
% of Time
7 8 9 10Avg Wind Speed
NNEESESSWWNW
Beach Patrol Rescue Reports
Daily Rip Current Risk1=Low2=Moderate3=High
Verification
0.92
0.570.620.58
0.370.32
00.10.20.30.40.50.60.70.80.9
1
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