Weather Patterns Associated With Florida Rip Current Deaths

Charles H. Paxton1,2, Jennifer M. Collins2, Kortnie J. Pugh1,2

1. National Weather Service, Tampa Bay Florida 2. University of South Florida, Tampa, FL

INTRODUCTION AND METHODOLOGYRip currents pose a significant threat to swimmers in ocean waters. Table 1 shows that Floridahad more rip current victims than any other state. Rip current death and injury reports from1994-2009 were collected from Storm Data (NCDC 2010). Sea level pressure (hPa) and wind (ms-1)mean and anomaly patterns were examined using NCEP reanalysis data (Kalnay et al., 1996). Thedata were plotted from day 0, the day of the event to day -3 which is 4 days before the event toexamine precursor patterns. The state was divided into four regions (Fig. 1) The panhandleregion stretches from the Florida border to the Suwannee River where 87 deaths and 106 injuriesoccurred. The Gulf coast region stretches from the Suwannee River to Flamingo with 19 deathsand 3 injuries in this region. The shallow water of Florida Bay and protective outer reefs of theKeys greatly reduce the threat for rip currents in that region. The Southeast coast stretches fromKey Largo to Jensen Beach where 70 deaths and 70 injures occurred. The East coast area fromJensen Beach north to the Florida border had 59 deaths and 20 Injuries reported.

RESULTS AND CONCLUSIONMost rip current deaths and injuries in Florida occur during the warmer months. Atpanhandle beaches from March, April and May (MAM) a southerly wind anomaly begins toincrease over the southwest Gulf of Mexico at day -3 and moves toward the panhandle. ForJune, July, August, and September (JJAS) the wind anomaly develops over the westernCaribbean and translates north to the panhandle. Along the gulf coast during MAM, asoutherly wind anomaly develops and persists becoming west on day 0. During JJAS apersistent southwest wind anomaly increases over the east gulf by day 0. Along the eastcoast during MAM a long northeast anomaly develops and increases by day 0. For JJAS thepattern is weaker with a more easterly anomaly. Along the southeast coast a wind maxanomaly develops east of the Bahamas and translates west. For JJAS a similar but weakerpattern develops. The results from this study are intended to provide a guide for issuing ripcurrent alerts several days in advance of the events.

Panhandle Gulf Coast East Coast SoutheastJun-Jul-Aug-SepJun-Jul-Aug-Sep Jun-Jul-Aug-Sep Jun-Jul-Aug-SepMar- Apr-May Mar- Apr-MayMar- Apr-MayMar- Apr-May

Top 5 States Deaths InjuriesFlorida 234 199

California 43 97

N. Carolina 36 14

N Jersey 22 27

Alabama 23 2

Top 5 Florida Counties

Deaths Injuries

Broward 32 41Escambia 31 46Miami-Dade 20 13Walton 20 1St. Johns 19 1

Table 1.Top five states with rip current deaths and injuries(Storm Data 1994-2009).

Table 2.Top five Florida Counties with rip current deaths and injuries (StormData 1994-2009).

Fig 1. Coastal divisions with rip current deaths and injurynumbers (deaths/injuries).

87/106

70/7019/3

59/20

Fig. 2a. Sea level pressure day 0 Fig. 3a. Sea level pressure day 0 Fig. 4a. Sea level pressure day 0 Fig. 4a. Sea level pressure day 0

Fig. 2b. SLP anomaly day 0 Fig. 3b. SLP anomaly day 0 Fig. 4b. SLP anomaly day 0 Fig. 5b. SLP anomaly day 0

Fig. 2c. Surface wind vector day 0 Fig. 3c. Surface wind vector day 0

Fig. 6a. Sea level pressure day 0

Fig. 6b. SLP anomaly day 0

Fig. 6d. Wind anomaly day 0

Fig. 6e. Wind anomaly day -1

Fig. 6f. Wind anomaly day -2

Fig. 6c. Surface wind vector day 0

Fig. 6g. Wind anomaly day -3

Fig. 4c. Surface wind vector day 0 Fig. 5c. Surface wind vector day 0

Fig. 2d. Wind anomaly day 0 Fig. 3d. Wind anomaly day 0 Fig. 4d. Wind anomaly day 0 Fig. 5d. Wind anomaly day 0

Fig. 2e. Wind anomaly day -1 Fig. 3e. Wind anomaly day -1 Fig. 4e. Wind anomaly day -1 Fig. 5e. Wind anomaly day -1

Fig. 2f. Wind anomaly day -2 Fig. 3f. Wind anomaly day -2 Fig. 4f. Wind anomaly day -2 Fig. 5f. Wind anomaly day -2

Fig. 7a. Sea level pressure day 0

Fig. 7b. SLP anomaly day 0

Fig. 7c. Surface wind vector day 0

Fig. 7d. Wind anomaly day 0

Fig. 7e. Wind anomaly day -1

Fig. 7f. Wind anomaly day -2

Fig. 7g. Wind anomaly day -3Fig. 5g. Wind anomaly day -3Fig. 4g. Wind anomaly day -3Fig. 3g. Wind anomaly day -3Fig. 2g. Wind anomaly day -3

Fig. 8a. Sea level pressure day 0

Fig. 8b. SLP anomaly day 0

Fig. 8c. Surface wind vector day 0

Fig. 8d. Wind anomaly day 0

Fig. 8e. Wind anomaly day -1

Fig. 8f. Wind anomaly day -2

Fig. 8g. Wind anomaly day -3

Fig. 5a. Sea level pressure day 0

Fig. 5b. SLP anomaly day 0

Fig. 5c. Surface wind vector day 0

Fig. 5d. Wind anomaly day 0

Fig. 5e. Wind anomaly day -1

Fig. 5f. Wind anomaly day -2

Table 3. Rip current deaths and injuries by month (Storm Data 1994-2009).

0

5

10

15

20

25

30

35

40

45

January February March April May June July August September October November December

Deaths

Fig.6g. Wind anomaly day -3Fig. 5g. Wind anomaly day -3