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Weather Patterns and
Social Aspects Associated
With United States Rip
Current Deaths
Charlie Paxton Science and Operations Officer
National Weather Service Tampa Bay Area
INTRODUCTION
Shepard (1936) first used the term “rip
current”:
• A circulation pattern of accumulated water
from waves rapidly flowing back out to sea
through narrow channels in the surf zone.
What is a Rip Current?
A strong
narrow (~10m)
current flowing
seaward.
Sand Bars at Low Tide
Shore break area
Outer sand bar
Deep channel
2010
64 Rip Current
29 Lightning
45 Tornado
0 Hurricane
34 Cold
42 Winter
33 Wind
Deeper water - waves don’t break.
It’s deceiving!
Types of Rip Currents
Types of Rip Currents
Flash: Short duration current (less than 10 minutes)
Unpredictable temporary conditions and variable
locations.
Types of Rip Currents
Traveling: Long
shore current)
pushes rip away
from original
location.
May push swimmer
into Flash,
Permanent, or Fixed
Rip current.
Wave Generation
Stronger wind, longer fetch = stronger waves
Wave energy is proportional to
amplitude or height squared
Waves of various sizes and
periods (speeds) are generated
Wave Period
• The longer the
period between waves: • The longer the
waves. • The faster the
waves move. • The more
momentum the waves carry.
Rip Current Animation
More drownings near low tide
0
2
4
6
8
10
12
14
16
No. of
Drownings
Hi
to
1
1
to
2
2
to
3
3
to
4
4
to
5
5
to
Lo
Lo
to
1
1
to
2
2
to
3
3
to
4
4
to
5
5
to
Hi
Tidal Times
Swell Period vs. Rip Currents
Stronger winds create
longer period swells
that move faster, have
more energy -
invigorate rips
Wave
Period
seconds
Wave
Speed
ms-1
5 8
6 9
9 14
11 17
13 19
14 21
How much current does it take?
Choppy conditions with
longer period waves
Choppy and
confused
conditions
may mask
someone
struggling in a
rip current.
Rip Current Reports
METHODOLOGY
Rip current death and injury reports were collected
from National Weather Service (NWS) Storm Data
(NCDC 2010).
The first rip current death and injury records were
entered by some NWS offices in 1994.
Other NWS offices have only begun providing records
within the past several years.
The Great Lakes, Hawaii, and Alaska areas were not
examined.
Injuries are typically listed in Storm Data when a near
drowning victim is taken to a hospital.
Top five states with rip current deaths
(Storm Data 1994-2009)
Top 5 States Deaths Injuries Coastline
Florida 234 199
2173 km
1067 km
(beaches)
California 43 97 1352 km
North Carolina 36 14 484 km
Alabama 23 2 85 km
New Jersey 22 27 209 km
Top five Florida counties with rip
current deaths (Storm Data 1994-2009)
Top 5 Florida
Counties
Deaths Injuries
Broward 32 41
Escambia 31 46
Miami-Dade 20 13
Walton 20 1
St. Johns 19 1
Florida divided into four regions
Beach Attendance Factors
•Season
•Weather
•Air Temp
•Time of day
•Water Temp
•Day of week
Water Temperatures
Rip current deaths typically occur in water is > 20 C.
Cold water decreases stamina and leads to muscle
cramping and hypothermia and alcohol increases
effects.
Alabama resort areas had 4 April cases but none
between November and March.
Florida Panhandle - 8 rip days in March and 11 in
April.
In California, someone has been killed or injured by
rip currents during every month.
U.S. rip current deaths by day of
week (Storm Data 1994-2009)
Ages
The average ages of victims was around 30.
California - youngest average age (26).
Florida - oldest average age (39).
In Florida the average age for rip current
deaths along the Southeast Coast was 45.
• 13% were 70 or older and under 5% the other
Florida regions.
CASE STUDY – Black
Sunday June 8th 2003
Eight People died on Black
Sunday in rough surf along
the Florida Panhandle”.
This was a terrible beginning
to an ill-fated summer with
20 Florida Panhandle rip
current deaths
Escambia and Walton
Counties are in the top five
Florida counties for rip
current deaths
Date County Deaths
09 May Santa Rosa 1
09 May Escambia 1
11 May Escambia 1
31 May Gulf 1
08 Jun Walton 6
08 Jun Okaloosa 2
09 Jun Escambia 1
02 Jul Bay 2
13 Jul Bay 1
30 Aug Escambia 2
31 Aug Escambia 2
Total 20
Rowan et al. (2004) in a Florida Department of Health study found:
8 of 12 drowning victims were male
10 were from out of state
3 had detectable levels of alcohol.
8 who drowned were attempting to rescue
someone who was struggling in the
water.
Most of those struggling were later saved.
Rowan et al. (2004)
Median age of the drowning victims was
46.5 years.
3 of the 12 drownings occurred in the
morning, and nine occurred in the
afternoon.
One of those who drowned was Larry
Lamotte, a CNN correspondent.
a. Surface chart b. Wind flow and speed (ms-1
)
Friday June 6th 2003
Complex Weather Pattern
Rain and Building Surf
Saturday June 7th 2003
Rain and Building Surf
a. Surface chart b. Wind flow and speed (ms
-1)
Buoy 42036 wind direction and speed 200 km west northwest of Tampa, FL
Buoy 42036 wave height and wave period 200 km west northwest of Tampa, FL
Black Sunday June 8th 2003
The rain has ended the waves have not
a. Surface chart b. Wind flow and speed (ms-1
)
Wind and Sea Level Pressure Averaging
METHODOLOGY
Winter = November through April.
Summer = May through October.
Surface wind (ms-1) and Sea level pressure
(hPa) mean and anomaly patterns were
examined using NCEP reanalysis data (Kalnay
et al., 1996) through the interface at
http://www.esrl.noaa.gov/psd/.
Data plotted from day 0 to day -4 (4 days
before the event day)
METHODOLOGY
Areas Examined
Florida
• Panhandle
• Southwest
• Southeast
• East
Texas
Alabama
South Carolina
North Carolina
Delaware
New Jersey
New York
California
South-
east
Florida
Summer
Increasing
easterly
flow
Figure 1c.1 Southeast Florida Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Day -4
Figure 1c.1 Southeast Florida Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Figure 1c.1 Southeast Florida Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Day -3
Figure 1c.1 Southeast Florida Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Day -1
Figure 1c.1 Southeast Florida Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Day -1
Figure 1c.1 Southeast Florida Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Day 0
Alabama
Winter
Increasing
southerly
flow
Figure 3.2 Alabama Winter (4 cases) Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
Figure 8.1 New York Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
New
York
Summer
Increasing
Southerly
flow
Tropical Storm Ophelia near Florida and
Hurricanes Maria and Nate swells affecting New York and New Jersey 7 September 2005
California
Summer
Figure 9.1 California Summer Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0
-1
-2
-3
-4
DAY 0
CONCLUSIONS
Typical weather patterns influencing rip currents are
associated with the subtropical high at the lower
latitudes and by more transient low pressure
systems in the higher latitudes
Onshore winds create greater rip current death
conditions.
Onshore winds create choppy disturbed waves that
are more likely to catch a swimmer by surprise
Rough conditions may also mask or hide someone in
distress from potential rescuers.
CONCLUSIONS
The results from this study are intended to provide
guidance for issuing rip current forecasts several
days in advance of the events.
Records vary from state to state.
Some factors are not easily discernable such as the
individual’s abilities and experience.
Most rip current deaths and injuries occur during the
warmer months and on weekends when more people
are at the beach
Future work: Related nearby buoy data to drownings.
Standardized
signage at many
beach access
points
Education
Where do most rip current
deaths occur?
At
unguarded
beaches!
Lifeguards
save lives
