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Charlie Paxton "Weather Patterns" NDPA Symposium 2012


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  • 1. Weather Patterns andSocial Aspects Associated With United States Rip Current Deaths Charlie Paxton Science and Operations Officer National Weather Service Tampa Bay Area
  • 2. 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.
  • 3. What is a Rip Current? A strong narrow (~10m) current flowing seaward.
  • 4. Sand Bars at Low Tide Outer sand bar Deep channel Shore break area
  • 5. 201064 Rip Current29 Lightning45 Tornado0 Hurricane34 Cold42 Winter33 Wind
  • 6. Deeper water - waves don’t break. It’s deceiving!
  • 7. Types of Rip Currents
  • 8. Types of Rip Currents Flash: Short duration current (less than 10 minutes) Unpredictable temporary conditions and variable locations.
  • 9. Types of Rip Currents Traveling: Long shore current) pushes rip away from original location. May push swimmer into Flash, Permanent, or Fixed Rip current.
  • 10. Wave GenerationStronger wind, longer fetch = stronger waves
  • 11. Wave energy is proportional toamplitude or height squared
  • 12. Waves of various sizes andperiods (speeds) are generated
  • 13. Wave Period• The longer the period between waves: • The longer the waves. • The faster the waves move. • The more momentum the waves carry.
  • 14. Rip Current Animation
  • 15. More drownings near low tide 16 14 12 10 No. of 8Drownings 6 4 2 0 Hi 1 2 3 4 5 Lo 1 2 3 4 5 to to to to to to to to to to to to 1 2 3 4 5 Lo 1 2 3 4 5 Hi Tidal Times
  • 16. Swell Period vs. Rip Currents Wave Wave Period SpeedStronger winds create seconds ms-1longer period swells 5 8that move faster, have 6 9more energy - 9 14invigorate rips 11 17 13 19 14 21
  • 17. How much current does it take?
  • 18. Choppy conditions with longer period waves Choppy and confused conditions may mask someone struggling in a rip current.
  • 19. 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.
  • 20. Top five states with rip current deaths (Storm Data 1994-2009) Top 5 States Deaths Injuries Coastline 2173 km Florida 234 199 1067 km (beaches) California 43 97 1352 kmNorth Carolina 36 14 484 km Alabama 23 2 85 km New Jersey 22 27 209 km
  • 21. Top five Florida counties with rip current deaths (Storm Data 1994-2009)Top 5 Florida Deaths InjuriesCountiesBroward 32 41Escambia 31 46Miami-Dade 20 13Walton 20 1St. Johns 19 1
  • 22. Florida divided into four regions
  • 23. Beach Attendance Factors•Season•Weather•Air Temp•Time of day•Water Temp•Day of week
  • 24. 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.
  • 25. U.S. rip current deaths by day of week (Storm Data 1994-2009)
  • 26. 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.
  • 27. Date County DeathsCASE STUDY – Black 09 May Santa Rosa 1Sunday June 8th 2003 09 May Escambia 1 11 May Escambia 1 Eight People died on Black 31 May Gulf 1 Sunday in rough surf along 08 Jun Walton 6 the Florida Panhandle”. 08 Jun Okaloosa 2 This was a terrible beginning to an ill-fated summer with 09 Jun Escambia 1 20 Florida Panhandle rip 02 Jul Bay 2 current deaths 13 Jul Bay 1 Escambia and Walton 30 Aug Escambia 2 Counties are in the top five Florida counties for rip 31 Aug Escambia 2 current deaths Total 20
  • 28. 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.
  • 29. 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.
  • 30. Friday June 6th 2003 Complex Weather Pattern Rain and Building Surfa. Surface chart b. Wind flow and speed (ms-1)
  • 31. Saturday June 7th 2003 Rain and Building Surfa. Surface chart b. Wind flow and speed (ms-1)
  • 32. Buoy 42036 wind direction and speed 200 km west northwest of Tampa, FL
  • 33. Buoy 42036 wave height and wave period 200 km west northwest of Tampa, FL
  • 34. Black Sunday June 8th 2003 The rain has ended the waves have nota. Surface chart b. Wind flow and speed (ms-1)
  • 35. 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 Data plotted from day 0 to day -4 (4 days before the event day)
  • 36. METHODOLOGY Areas Examined Florida  South Carolina • Panhandle  North Carolina • Southwest  Delaware • Southeast • East  New Jersey Texas  New York Alabama  California
  • 37. Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) DaySouth- 0eastFlorida -1 Summer -2Increasingeasterlyflow -3 -4
  • 38. Day -4
  • 39. Day -3
  • 40. Day -1
  • 41. Day -1
  • 42. -1Wind anomaly (ms ) Day 0
  • 43. Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0Alabama Winter -1Increasing -2 southerly flow -3 -4
  • 44. Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) DayNew 0YorkSummer -1IncreasingSoutherlyflow -2 -3 -4
  • 45. Tropical Storm Ophelia near Florida and Hurricanes Maria and Nate swells affectingNew York and New Jersey 7 September 2005
  • 46. CaliforniaSummer DAY 0
  • 47. 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.
  • 48. 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.
  • 49. Education Standardized signage at many beach access points
  • 50. Where do most rip currentdeaths occur? At unguarded beaches!
  • 51. Lifeguardssave lives