Post on 24-Jan-2022
transcript
Bill SammlerWarning Coordination Meteorologist
National Weather Service – Wakefield, VA
VA Beach Summer Symposium - Hurricane
DynamicsWinds, Storm Surge and
Rainfall
Let’s Start with Rainfall
Track
Tropical Cyclone RainfallHurricane Irene – 2011 vs. Floyd - 1999
Track
Tropical Cyclone RainfallHurricane Irene – 2011 vs. Isabel - 2003
The Anatomy of the post-Matthew
Flood
Overview• Third Significant Rainfall
Event in 6 weeks• Interaction with Cold Front
Enhanced Winds near the coast (SE VA/NE NC)– Matthew Not Truly Tropical
• Storm Surge/Beach Erosion a Problem
• Track Forecasts Were As Not Helpful in Assessing Potential Impacts As They Normally Are
Hurricane Matthew Track
Hurricane Matthew Rainfall
Track
Salient Points• Widespread Major Floods
Rarely Result from a Single Heavy Rain Event
• Antecedent Moisture Conditions Play a Critical Role
• Heavy Rainfall in September Made Matthew’s Flooding Possible
• Rainfall Pattern Resulted in Unusual Impacts
September Rainfall
Hurricane Matthew Rainfall
Where Does the Water Go?
Max Rainfall September through Matthew
River Graph – Lawrenceville VA
Lawrenceville, VA -9/15 to 10/18
~2 ft.
~+20 ft.
~3 ft.~4 ft.
River Graph – Franklin VA
Franklin, VA - 9/15 to 10/18
~+6 ft.
~+13 ft.
~1.0 ft.
~3.5 ft.
Tidal vs. River Graphs
Tidal vs. River Graphs
Tidal vs. River GraphsSouth Mills, NC - 9/15 to 10/18
“Record” Stage
6 Days above
“record” stage!!
~6.5 ft.
~7.5 ft.
Storm Surge Dynamics
Storm Surge DefinitionSTORM 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
Wave effects, which cause most coastal damage, are not accounted for in storm surge measurements
Storm SurgeStorm 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)
Katrina and Sandy Examples
Union Beach, NJ (blog, Spleeness)Long Beach, NJ (White House photo – Sonya Hebert)
Biloxi, MS (NOAA) Biloxi, MS (NOAA)
Storm Surge
Storm Surge is highest and
Winds are greatest in the RIGHT FORWARD
QUADRANT close to where center makes landfall
Storm Surge vs. Location Relative to Storm
Storm Surge ExampleFACTOR = STORM DIRECTION
CAT 2 Max Surge
CAT 2 NE 20 mph
Storm Surge ExampleFACTOR = STORM DIRECTION
CAT 2 Max Surge
CAT 2 N 20 mph
Storm Surge ExampleFACTOR = STORM DIRECTION
CAT 2 Max Surge
CAT 2 WNW 20 mph
Hurricane Winds
Hurricane Wind Characteristics
• Strongest along the coast/over water, and near the center of well developed systems– Weaker/weakening systems have more chaotic
wind field
• Systems becoming non-tropical are the most difficult to forecast relative to winds (e.g Matthew – 2016)
• Hampton Roads has not experienced true hurricane winds in decades
Hurricane Irene (2011) Winds
Matthew Peak Gusts
Matthew plus Cold Front
Matthew only
The End!!Are There Any Additional
Questions?
william.sammler@noaa.gov