Tropical Cyclone Tornadoes

Tropical Cyclone Information and Their Impacts Tropical Cyclones Since 1870

Norfolk

Tropical Cyclone Probabilities – By Month Hurricane Return Periods Recent Improvements in Track Forecasts Have Resulted in Less Uncertainty

REMEMBER: This Cone represents a 67% likelihood the storm will remain within that cone in the next 5 days. Up to 1/3 of the time, it won’t.

72 hour circle Image courtesy of Brian McNoldy, University of Miami Research Associate radius

 A five-day forecast now is more accurate than a three-day forecast 1990s – 225 nm was two decades ago! 2000s – 150 nm  A two-day forecast now is as accurate as a one-day forecast was a decade ago! 2019 – ~75 nm Michael Track Example (2018) Florence Track Example (2018) Florence Track Example (2018)

5 AM Sunday, Sept 9th 5 AM Friday, Sept 14th

National Hurricane Center predicted the spot where Hurricane Florence would make landfall within 2 miles of reality 5 days out. Cone of Uncertainty Widely used but still misunderstood

• The cone does not tell you anything about the size of the storm.

• The cone does not tell you anything about the actual uncertainty associated with the forecast, since the size of the cone is fixed at each forecast interval.

• Nothing magically happens at the edge of the cone. If a hurricane is approaching and you are scrutinizing each new forecast to see if you are inside the cone or not, you are missing the point of it. It is arbitrarily chosen to be the 67% historical probability threshold. Cone of Uncertainty Widely used but still misunderstood

• At each forecast point, there is a letter written inside the black dot corresponding to a general intensity range: D (tropical depression), S (tropical storm), H (hurricane), and M (major hurricane (Category 3+)).

• ***The cone does not tell you anything about where impacts will be experienced. Even for a perfect down-the-middle track forecast, impacts such as strong wind, heavy rain, storm surge, and tornadoes will extend beyond the cone.*** Location of Impacts • Especially in the mid Atlantic, wind impacts can be felt well away from the center of the storm. Wind Impacts

• Worst winds normally near and to the right of the center of the storm. • However, wind impacts can be well removed from the center of circulation, especially across the mid Atlantic and NE states as the hurricane interacts with high pressure to the north. Hurricane Hermine (2016) Track/Peak Winds Wind Impacts (Continued)

Hurricane Matthew 2016 Track/Peak Winds Location of Impacts • Especially in the mid Atlantic, wind impacts can be felt well away from the center of the storm.

• Favored region for tornadic development is the Eastern semi-circle. Tropical Cyclone Tornadoes

Tornadoes far from the Center Tropical Cyclone Tornadoes

• Nearly 70% of landfalling hurricanes (1948-2000) spawned at least 1 tornado • 40% spawn more than 3 tornadoes • Some hurricanes produce tornado “outbreaks” – Hurricane Beulah (1967): 141 – Hurricane Ivan (2004): 117 – Hurricane Frances (2004): 101 – Hurricane Rita (2005): 90 – Hurricane Camille (1969): 80 – Hurricane Katrina (2005): 43 – Hurricane Florence (2018): 44 Location of Impacts • Especially in the mid Atlantic, wind impacts can be felt well away from the center of the storm.

• Favored region for tornadic development is the Eastern semi-circle.

• Heaviest rainfall is often found on the western semicircle due to interaction with a frontal boundary and dry air entraining on east side of storm. Tropical Cyclone Rainfall Hurricane Matthew – 2016 & Michael – 2018

Track Location of Impacts • Especially in the mid Atlantic, wind impacts can be felt well away from the center of the storm.

• Favored region for tornadic development is the Eastern semi-circle.

• Heaviest rainfall is often found on the western semicircle due to interaction with a frontal boundary and dry air entraining on east side of storm.

• Most deaths from tropical systems occur because of flooding. Flooding Impacts • Especially in the mid Atlantic, wind impacts can be felt well away from the center of the storm.

• Favored region for tornadic development is the Eastern semi-circle.

• Heaviest rainfall is often found on the western semicircle due to interaction with a frontal boundary and dry air entraining on east side of storm.

• Most deaths from tropical systems occur because of flooding. Flooding Impacts • Especially in the mid Atlantic, wind impacts can be felt well away from the center of the storm.

• Favored region for tornadic development is the Eastern semi-circle.

• Heaviest rainfall is often found on the western semicircle due to interaction with a frontal boundary and dry air entraining on east side of storm.

• Most deaths from tropical systems occur because of flooding. Location of Impacts