BRAV/APC Meeting 06/23/2015
Mid Atlantic Hurricane Background Info, Storm Surge, Lightning and Tornado Safety, NWS Resources and More
Bill Sammler Warning Coordination Meteorologist National Weather Service – Wakefield, VA Tropical Cyclones Since 1870
Norfolk
Cape Hatteras Hurricanes Since 1870
Norfolk
1933 Hurricane
Cape Hatteras 2015 Hurricane Season Forecast
NOAA Forecast - Issued May 28th
“NORMAL” • 6‐11 Named Storms 12 storms
• 2‐5 Hurricanes 6 hurricanes
• 0‐2 Major Hurricane 2 major (Cat 3+) hurricanes
70% Chance of a Below Normal Season due to El Nino and relatively cool tropical Atlantic Ocean waters What Season is This?
1992 What Season is This?
1972 Hurricane Season Predictions The Seasonal Forecast Fallacy
Graphic Courtesy Steve Lyons What Season is This?
2010 Recent Improvements in Track Forecasts Have Resulted in Less Uncertainty 2005 Operational Cone
REMEMBER: 2015 Cone 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. Hurricane Threats STORM SURGE – The abnormal rise in water level directly associated with the wind and pressure forces associated with a hurricane
Storm Surge Example – hurricane makes landfall at high tide
Storm Surge is highest in right forward quadrant near center as it crosses coast Storm Surge Storm Surge Factors • Storm Intensity and Size – Stronger = Higher Surge – Larger = Larger Area Affected • Storm Speed – Slower Often Means Higher Surge • Angle to Coast at Landfall – Perpendicular Maximizes Surge (Katrina) Storm Surge Example FACTOR = STORM INTENSITY
CAT 1 NNW 20 mph
CAT 3 NNW 20 mph Sandy vs. Irene
Sandy (2012)
Irene (2011) Storm Surge Example FACTOR = STORM SPEED
CAT 3 NNW 10 mph
CAT 3 NNW 30 mph Storm Surge Example FACTOR = ANGLE TO COAST
CAT 3 N 20 mph
CAT 3 WNW 20 mph Sandy vs. Irene
Sandy (2012)
Irene (2011) What About Evacuation?
Storm Motion Directions that Necessitate OBX Evacuation What About Evacuation?
Storm Motion Directions that Necessitate H.R. Evacuation
Storm Motion With significant Impact but Limited/No Evacuation Location of Impacts
• 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 (northward moving storms)
• Winds generally strongest on the right (eastern) side of the storm after landfall, with friction lowering winds over land vs. water Fresh Water Flooding
Tropical Storm Debby – Sopchoppy, FL
Hurricane Irene – Vermont • Up to 43 inches of rain have fallen in 24 hours in a single tropical cyclone (Alvin, TX – Claudette 1979). • TC rainfall potential depends most on the speed of motion. Slow- moving systems produce the most rainfall. • Tropical depressions or storms can produce more rain than hurricanes! Tropical Cyclone Rainfall Hurricane Floyd - 1999
Floyd Track Tropical Cyclone Rainfall Hurricane Irene - 2011
Track Tropical Cyclone Rainfall Hurricane Irene – 2011 vs. Isabel - 2003
Track 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 Tropical Cyclone Tornadoes
All Tropical Cyclones Hurricanes
Tropical Depressions
Tropical Storms Tropical Cyclone Tornadoes Gaston, Frances and Ivan - 2004
Mainly Ivan – 9/17/2004
Mainly Gaston – 8/31/2004
69 Tornadoes in 3 weeks. Previous annual record – 31!! Hurricane Wind Examples Sandy vs. Irene
Sandy (2012)
Irene (2011) Irene –NHC vs. Reality
Irene (NHC) Irene (reality) Isabel –NHC vs. Reality
Isabel (NHC) Isabel (reality) Thunderstorm and Heat Safety Thunderstorm Hazards
Tornadoes Hail
Lightning Damaging Winds