1. Hurricane Season Preparedness 2019
National Weather Service
New Orleans/Baton Rouge
Weather Forecast Office

2. 2018 Seasonal Recap 15 Tropical Storms 6 Hurricanes 2 Major Hurricanes
Notable Storms:
BOTH major hurricanes affected the US
Florence – winds weakened before landfall, but still produced catastrophic flooding
Michael – landfall as a category 4 resulting in widespread wind and storm surge damage
2005 is still the most active with 28 named storms, and 7 of them major hurricanes

3. Colorado State U. Forecast Caution: it only takes one
2019 Seasonal Outlook
Average
Colorado State U. Forecast
NOAA forecast
(Release May 23)
Named Storms 12 13 ??
Hurricanes 6 5
Major Hurricanes 2
Caution: it only takes one

4. 2019 Seasonal Forecast Seasonal forecasts do NOT tell you:
Where storms will make landfall
How strong they will be at landfall
Seasonal forecasts only give a general idea of the potential for overall basin activity
Reality: We have to plan as though we will be impacted EVERY year

5. Lead Time is Great, but…
Five-day plans are great, but you won’t always have five days of lead time on the Gulf Coast

6. Lead Time is Great, but…
Five-day plans are great, but you won’t always have five days of lead time on the Gulf Coast
Hurricane Michael 2018
Wasn’t classified as a tropical storm until about 72 hrs before landfall as a category 5 hurricane
Intensified from 75 mph winds (category 1) to 130 mph winds (category 4) in 42 hours

7. Lead Time is Great, but…
Five-day plans are great, but you won’t always have five days of lead time on the Gulf Coast
Hurricane Camille 1969
Wasn’t classified as a tropical storm until about 80 hrs before landfall as a category 5 hurricane
Intensified from 75 mph winds (category 1) to 120 mph winds (category 3) in 24 hours

8. Lead Time is Great, but…
Five-day plans are great, but you won’t always have five days of lead time on the Gulf Coast
Hurricane Cindy 2005
Wasn’t classified as a tropical storm until about 48 hrs before landfall

9. Lead Time is Great, but…
Bottom Line: You won’t always have a 5 day lead time on Gulf of Mexico storms, so timetables need to be adaptable!
For thought… Could you execute your plan in only 3 days? How about as few as 2?

10. Hurricane Forecast Verification
Track forecast skill has improved tremendously
A 3-day forecast today is about as accurate as a 1-day forecast was in the 1990s
Since 2005 (Katrina), the 3-day forecast error has been cut in half (from ~190 miles in 2005 to ~90 miles in 2017)

11. Hurricane Forecast Verification
Intensity forecasts have only shown modest improvement
In 2017, the 48-hr intensity error was about 13mph, or approximately 1 Saffir-Simpson category
This is why planning for one category higher than forecast is still a good course of action

12. Rapid Intensification
One reason intensity forecasts aren’t improving as fast as track forecasts – rapid intensification
An increase of 30 kts (35 mph) in 24 hrs
Notable Examples:
Hurricane Michael 2018  90mph to 140mph in 24 hours (still rapidly intensifying up to landfall)
Hurricane Gustav  75mph to 145mph in 24 hrs (before landfall in Cuba)
Hurricane Katrina 2005  115mph to 170mph in 18 hrs
Hurricane Camille 1969  105mph to 175mph in 24 hrs

14. Atlantic Tropical Cyclone Deaths by Hazard
Flooding from storm surge and fresh water (rain) accounts for over three quarters of deaths directly attributable to Atlantic Basin Tropical Cyclones

15. The Storm Surge Threat

16. Factors Influencing Storm Surge
Where the circulation center crosses the coast
Direction of storm motion relative to the coast
Wind strength (storm intensity)
Radius of maximum winds (eye size)
Overall size of storm (outer wind radii)
Slope of the continental shelf
Shape of the coastline and other coastal features (barrier islands, bays, rivers, levees, etc)
…It’s Complicated!

17. Landfall Location - Comparison
Landfall to the west
Landfall in the middle
Landfall to the east
Bottom Line: Small changes in the storm can lead to big changes in the surge.

18. The Inland Flooding Threat

19. Factors Influencing Heavy Rainfall and Inland Flooding
Forward Speed (slower means more rain)
Size (bigger means more rain)
Rain Rate (atmospheric moisture content)
Vertical Wind Shear (more rain on one side)
Interaction With Fronts/Upper-Level Troughs
…It’s Complicated!

20. 2017 Hurricane Harvey Highest 6-day storm totals:
Nederland, TX: 60.58” – new US record!
Groves, TX: 60.54”

21. 2017 Tropical Storm Cindy
Heavy rain often falls in “bands” and can mean sharp gradients in recorded rainfall
It’s difficult to predict where these bands will set up more than a few hours in advance
Heavy rain often falls in “bands” and can mean sharp gradients in recorded rainfall.

22. Un-named Low: Rainfall Impacts

23. Rainfall Risk Considerations
Recurrence intervals like “100-year” or “1000-year” storm can be misleading
Those terms are really a representation of annual risk
100-year storm  1% annual flood risk
500-year storm  0.2% annual risk
1000-year storm  0.1% annual risk
Risk remains the same every year, even if a similar event happened recently!

24. Rainfall Risk Considerations
Flood risk is cumulative!

25. Product Review For the 2019 Hurricane Season

26. Time of Arrival Graphics
NHC Arrival Timing Graphics
Preparations become dangerous once winds reach TS force
Graphics account for forecast uncertainty (track/intensity/size)
“Earliest Reasonable” graphic - best for users with low tolerance for risk
“Most Likely” graphic - best for explaining when all preparations should be completed prior to onset of dangerous conditions

28. Heavy Rainfall Threat High Risk Days – Be Especially Vigilant
Even Moderate Risk days carry an increased risk of life threatening heavy rainfall - flooding.

29. Potential Storm Surge Flooding Map (Inundation)
This is ONLY surge flooding
NOT the forecast - “Reasonable” worst case
Only a 10% chance these values will be exceeded
Subtle changes possible with each update
No values shows inside risk reduction system

30. Storm Surge Watch/Warning
Storm Surge Watch – there is a possibility of life-threatening storm surge inundation within 48 hours
Storm Surge Warning –there is a danger of life-threatening storm surge inundation within 36 hours

31. Storm Surge Watch/Warning
Will be tone alerted via NOAA Weather Radio
Will likely be tone alerted via Wireless Emergency Alerts in 2019
CAN be issued for areas inside the risk reduction system

32. Storm Surge “Gotchas” Products only account for storm surge flooding
They do NOT include fresh water (rain) flooding
They do NOT include any drainage flooding (water flowing downstream)
Tone alerts through weather radio and WEA will likely “over warn” some areas
Weather radio alerts are parish/county based
WEA are sent by cell towers covering the warned area and can still result in “bleed over”

33. Some Final Thoughts… Every storm is different!
Pay attention to local NWS products (both official text products and graphics posted on social media and our website) and the local media to determine what the greatest impacts will be for the local area from a given storm.
Be careful where you get your information.
“Social mediarologists” sometimes post model forecasts with little context or explanation to get more “likes”. Single track model forecasts are almost never right, especially at long lead times. Make sure you’re getting information from a reliable and reasonable source.

34. National Weather Service New Orleans/Baton Rouge
Facebook: NWSNewOrleans
We answer the phones 24/7/365! Note: A recording will pick up and has some options for general information. If you have questions, there is an option to speak to a forecaster.