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Charlie Paxton "Weather Patterns" NDPA Symposium 2012

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Charlie Paxton "Weather Patterns" NDPA Symposium 2012

  1. 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. 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. 3. What is a Rip Current? A strong narrow (~10m) current flowing seaward.
  4. 4. Sand Bars at Low Tide Outer sand bar Deep channel Shore break area
  5. 5. 201064 Rip Current29 Lightning45 Tornado0 Hurricane34 Cold42 Winter33 Wind
  6. 6. Deeper water - waves don’t break. It’s deceiving!
  7. 7. Types of Rip Currents
  8. 8. Types of Rip Currents Flash: Short duration current (less than 10 minutes) Unpredictable temporary conditions and variable locations.
  9. 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. 10. Wave GenerationStronger wind, longer fetch = stronger waves
  11. 11. Wave energy is proportional toamplitude or height squared
  12. 12. Waves of various sizes andperiods (speeds) are generated
  13. 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. 14. Rip Current Animation
  15. 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. 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. 17. How much current does it take?
  18. 18. Choppy conditions with longer period waves Choppy and confused conditions may mask someone struggling in a rip current.
  19. 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. 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. 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. 22. Florida divided into four regions
  23. 23. Beach Attendance Factors•Season•Weather•Air Temp•Time of day•Water Temp•Day of week
  24. 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. 25. U.S. rip current deaths by day of week (Storm Data 1994-2009)
  26. 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. 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. 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. 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. 30. Friday June 6th 2003 Complex Weather Pattern Rain and Building Surfa. Surface chart b. Wind flow and speed (ms-1)
  31. 31. Saturday June 7th 2003 Rain and Building Surfa. Surface chart b. Wind flow and speed (ms-1)
  32. 32. Buoy 42036 wind direction and speed 200 km west northwest of Tampa, FL
  33. 33. Buoy 42036 wave height and wave period 200 km west northwest of Tampa, FL
  34. 34. Black Sunday June 8th 2003 The rain has ended the waves have nota. Surface chart b. Wind flow and speed (ms-1)
  35. 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 http://www.esrl.noaa.gov/psd/. Data plotted from day 0 to day -4 (4 days before the event day)
  36. 36. METHODOLOGY Areas Examined Florida  South Carolina • Panhandle  North Carolina • Southwest  Delaware • Southeast • East  New Jersey Texas  New York Alabama  California
  37. 37. Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) DaySouth- 0eastFlorida -1 Summer -2Increasingeasterlyflow -3 -4
  38. 38. Day -4
  39. 39. Day -3
  40. 40. Day -1
  41. 41. Day -1
  42. 42. -1Wind anomaly (ms ) Day 0
  43. 43. Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) Day 0Alabama Winter -1Increasing -2 southerly flow -3 -4
  44. 44. Vector Wind (ms-1) Wind anomaly (ms-1) Sea level pressure (hPa) DayNew 0YorkSummer -1IncreasingSoutherlyflow -2 -3 -4
  45. 45. Tropical Storm Ophelia near Florida and Hurricanes Maria and Nate swells affectingNew York and New Jersey 7 September 2005
  46. 46. CaliforniaSummer DAY 0
  47. 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. 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. 49. Education Standardized signage at many beach access points
  50. 50. Where do most rip currentdeaths occur? At unguarded beaches!
  51. 51. Lifeguardssave lives