Hurricane Isaac. National Weather Service. Communication Challenges and The Future. Weather Forecast Office New Orleans/Baton Rouge

Transcription

1 Hurricane Isaac Communication Challenges and The Future National Weather Service Weather Forecast Office New Orleans/Baton Rouge

2 Hurricane Isaac Challenges

3 2012 Tropical Season Season was quiet for Louisiana and Mississippi until Isaac

4 Satellite Imagery *Tropical Storm *Not forecast to be a hurricane until just before landfall *Asymmetric convective structure for days *Not very eye catching

5 Tropical Storm 1130 AM Tue Aug 28 Nearing Hurricane Strength

6 Hurricane Isaac Aug 28 Night Imagery

7 Model Tracks The Euro takes it here The GFS takes it here My model takes it here NHC takes it here New alert: The new GFS takes Isaac further west, but the new Euro goes further east

8 Saturday August 25, 4pm ~84 hours before actual 2 nd landfall Small portion of SE LA in the error cone

9 Sunday August 26, 4am ~72 hours before actual 2 nd landfall Westward shift with SE LA now inside the cone Hurricane Watch issued for St. Bernard, MS Coast Plaquemines Potential Category 2 in less than 72 hrs

10 Sunday August 26, 10am ~66 hours before actual 2 nd landfall Continued westward shift with increased impacts for SE LA Hurricane Watch issued for all of SE LA Potential Category 2 in less than 72 hrs

11 Sunday August 26, 10am H-hour based on Advisory 22 (Sunday 10am) Forecast onset of TS winds ~7am Tuesday (~45 hours out)

12 Sunday August 26, 4pm ~60 hours before actual landfall Track nudged slightly farther westward Hurricane Warning issued All guidance suggests SLOW MOVING cat 1 or low end cat 2

13 Sunday August 26, 4pm H-hour based on Advisory 23 (Sunday 4pm) Forecast onset of TS winds 12am- 3am Tuesday (~34 hours out)

14 Monday August 27, 10am ~42 hours before actual landfall Track nudged very slightly westward Forecast category 1 at coast Slow forward motion and large size Significant storm surge threat

15 Hurricane Isaac Storm Surge Forecast

16 What Impacts Storm Surge? Track

17 Single Track Storm

18 Single Track Storm Surge Plot

19 Single Track Storm Surge Plot

20 What Impacts Storm Surge? Track Forward Speed

21 Gustav SLOSH estimate using 50 nm RMW

22 Gustav SLOSH estimate if ~10 kts slower

23 What Impacts Storm Surge? Track Forward Speed Coastline Bathymetry and Geographic Shape

24 Wide shelf/ gentle slope Narrow shelf/ sharp slope

25 Single Track Storm Surge Plot

26 What Impacts Storm Surge? Track Forward Speed Coastline Bathymetry and Geographic Shape Radius of Mean Winds (RMW)

27 RMW = 25 mi., Average Size

28 Actual RMW = 6 mi.

29 What Impacts Storm Surge? Hurricane Isaac Track very vulnerable track Forward Speed very slow Coastline water had plenty of time to funnel into the lowest areas Bathymetry and Geographic Shape Radius of Mean Winds (RMW) 45 to 50 mile RMW (double the average)

30 Products and Services During Isaac

31 Current Products and Services During Isaac Text Graphic Briefings PowerPoint Hundreds of telephone calls

32 Local Action Statement

33 Worst case storm surge potential for all locations Cat 2 Hurricane moving NNW 10 MPH

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37 Tropical Cyclone Coastal Flooding Impact Graphic 421 am cdt Mon Aug 27, Extreme threat level for Lake Pontchartrain and areas east of MS River Coastal flooding impacts defined locally and available on website next to coastal flooding potential impact graphic.

38 Storm Surge Forecast Monday Aug 27, 5am ~48 hrs before actual 2 nd landfall

39 P-Surge of 4 Feet or more NHC Advisory am cdt Mon Aug 27, 2012

40 P-Surge of 4 Feet or more NHC Advisory am Wed Aug 29, 2012

41 Hurricane Isaac How did the physical science do?

42 Storm Surge Location Est. Surge (feet), date, est. with tide) Point-a-la-Hache (Plaquemines) / Shell Beach (St Bernard) / Waveland Yacht Club (Hancock) / South of Lafitte (Jefferson) 8.5 9/ Rigolets at Hwy 90 (Orleans) 7.0 9/ Mandeville (St Tammany) 7.0 9/ Bayou Liberty Slidell (St Tammany) 7.5 9/ Gonzales Panama Canal (Ascension) 6.5 9/ Biloxi Back Bay (Harrison) 6.5 9/ Pass Manchac LaPlace (St John the Baptist) 5.5 9/ Pilot Town (Plaquemines) / Grand Isle (Jefferson) 4.5 9/

43 Wind Duration Forecast Sunday Aug 26, 12pm Initial wind duration forecast included in the 12pm SE Task Force briefing (and also in the 2pm EM briefing): Tropical Storm wind duration: 24 hours for most locations with a few locations up to 36 hours Hurricane force wind duration: 6 to 8 hours in areas within direct path

44 Wind Duration Forecast Tuesday Aug 28, 7am Duration forecasts were tweaked as forecasts were adjusted for change in path and forward speed Location Tropical Storm Force Duration (Sustained) Hurricane Force Duration (Along track and in squalls) Lower Plaquemines Lower St. Bernard South Shore North Shore Hancock County LA Florida Parishes LA River Parishes Harrison County Jackson County SW MS E Central LA hrs 6-10 hrs hrs 4-8 hrs hrs 1-3 hrs hrs 1-3 hrs hrs gusts possible

45 Rain Forecast Sunday Aug 27, 12pm When model guidance began shifting westward and a westward shift looked likely in the NHC track, NWS New Orleans included the following in the 12pm SE Task Force and 2pm EM briefings: Rainfall: 12 to 16 inches. Highest threat along and east of track. Higher, up to 20 inches in rainbands

46 Rain Forecast Forecast rainfall values from NWS New Orleans changed very little with at least 10 inches forecast across the area once the track began to shift westward All briefings beyond Sunday evening specifically explained that slow movement would lead to significant heavy rainfall threat

47 Rain Forecast Sunday Aug 27, 1pm HPC graphics continue to indicate heaviest rain east of local area (farther east track) NWS New Orleans: Storm total of 15 to 18 inches expected, some higher amounts possible. Flash Flood Watch now in effect for entire area.

48 Rain Forecast Sunday Aug 27, 7pm HPC graphics begin to spread heavier rainfall westward NWS New Orleans: Storm total of 10 to 16 inches expected, some higher amounts possible. Slow movement means greater threat of heavy rain.

49 Rain Forecast Monday Aug 28, 4pm HPC graphics spread heavy rainfall across the whole area NWS New Orleans: Storm total of 10 to 15 inches expected, some higher amounts possible. Slow movement means greater threat of heavy rain.

50 Rainfall Accumulation Radar rainfall estimates show large swaths of 12 to 16 inches (red) and averages of 6 to 12 inches (yellow and orange)

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52 Estimated Isaac Rainfall

53 Some Rainfall Totals Location Rain Total (inches) Pascagoula 3 NE New Orleans Carrollton Biloxi Hammond Reserve Picayune McComb Robert Galliano Slidell Kentwood Baton Rouge Sherwood 9.21

54 River Flooding Forecast Thursday Aug 30, 7am

55 Historic River Flood Event Location Wolf near Landon Wolf near Gulfport Hobolochitto near Caesar Tangipahoa near Kentwood Tangipahoa near Robert Amite near Maurepas Pearl near Pearl River Bogue Chitto near Tylertown Bogue Chitto near Franklinton Bogue Chitto near Bush Biloxi near Wortham Tchefuncte near Covington Bogue Falaya at Camp Covington Jourdan near Kiln Crest (feet) (record) (record) (record) (major) (major) 7.48 (major) (major) (major) (major) (major) (major) (moderate) (moderate) 9.69 (moderate)

56 Tornadoes County/Parish Location EF Rating Harrison Gulfport EF-1 Jackson Ocean Springs EF-1 Jackson Pascagoula EF-2

57 Hurricane Isaac Social Science Challenges

58 Saffir-Simpson Scale Categorizes hurricanes into 5 levels of intensity based on wind speeds alone Just a category 1 or Only a tropical storm Ignores other threats such as wind duration, storm surge, heavy rainfall, river flooding, etc Gives people a dangerous false sense of safety/security

59 SLOSH SLOSH graphics tied to Saffir-Simpson categories despite the fact that the Saffir- Simpson scale is now wind-only Category 1 scenarios did not accurately portray Isaac s threat due to large size and slow motion NWS New Orleans attempted to combat this by briefing using category 2 graphics and explaining the higher than typical values NWS New Orleans turned to the media to help communicate these extreme impacts

60 Storm Comparisons and Personal Experiences Every storm is different, but people have a natural tendency to draw from personal experience We didn t flood in Katrina My house has never flooded in 50 years The surge forecast was similar for Gustav and we didn t flood then

61 Hurricane Isaac Where do we go now?

62 P-Surge 4 ft or more NHC Advisory 25 4 am cdt Mon Aug

63 10% P-Surge Exceedance Typical Level of Confidence NHC Advisory 25 4 am cdt Mon Aug 27, 2012

64 20% P-Surge Exceedance High Level of Confidence NHC Advisory 25 4 am cdt Mon Aug 27, 2012

65 30% P-Surge Exceedance Higher Level of Confidence NHC Advisory 25 4 am cdt Mon Aug 27, 2012

66 50% P-Surge Exceedence Highest Level of Confidence NHC Advisory 25 4 am cdt Mon Aug 27, 2012

67 Probabilistic Inundation Hurricane Surge (PIHS) P-Surge Exceedance height above ground. 10 % - Typical Level of Confidence 20 % - High Level of Confidence 30 % - Higher Level of Confidence 50 % - Highest Level of Confidence Probability of Inundation of Hurricane Surge greater than 4 feet.

68 Inundation Graphics Datum Issues Pretty Picture Issues Pretty does not equal accuracy! Need to be accurate and easy to understand The vast majority of storm surge forecast error is in the meteorology. In the heat of the battle, one MUST not go with one forecast graphic. Uncertainty must play a big role

69 The Social Science of Categories Moving away from Categories Products Graphics Evacuations Response

70 Storm Surge Warning

71 Storm Surge Warning Example Hurricane Isaac

72 Training Storm Surge Warning Inundation Graphics Probabilistic Information Storm Surge Science Concentration on Impacts not the skinny black line and the category Where to get information and how to sort out all that information