r.h. weisberg and l. zheng fwri marine quest 04/09/05

A Numerical Simulation of the Hurricane Charley Storm Surge in the Light of Lessons

Learned from Tampa Bay

R.H. Weisberg and L. Zheng

FWRI Marine Quest

04/09/05

Submergence based on a 5-foot uniform sea level rise

Submergence based on a 10-foot uniform sea level rise

Submergence based on a 20-foot uniform sea level rise

Hurricane Storm Surge Simulation Requirements

1) A high resolution numerical circulation model with capabilities for flooding and drying land.

2) Accurate wind and pressure fields.

3) High resolution bathymetry and elevation data.

Hydrodynamic Model: FVCOM

3) Incorporating flooding/drying skill which is critical for storm surges study.

Advantages:

1) Using unstructured triangle grid to better represent complex coastal and estuarine geometry.

2) Using simple finite-difference which has simple discrete structures and computational efficiency.

Prototypical Hurricane Structure (Holland, 1980)

Merged bathymetry and topography

Lessons learned from Tampa Bay

Based on prototypical category 2 and 4 storms that approach the region from several different directions, at different approach speeds, and making landfall at different locations.

http://ocg6.marine.usf.edu

Model Grid for Tampa Bay Storm Surge Experiment

Minimum resolution: 100 m

Category 2 storm translating at 5 m/s

Courtney Compbell Causeway

W. Howard Frankland Bridge

Gandy Bridge

Sunshine Skyway B

ridge

24 Hour

OCG @ USF

St. Pete

Tampa

28 Hour

OCG @ USF

Tampa

St. Pete

30 Hour

OCG @ USF

St. Pete

Tampa

Case I: IRB landfall from the west.

Case II: Translation up the Bay.

Case III: Coast parallel from the south Case IV: Coast parallel from the north

Arrow: landfall time

Courtney Compbell Causeway

W. Howard Frankland Bridge

Gandy Bridge

Sunshine Skyway B

ridge

Category 2 storm translating at 5 m/s

Case I: IRB landfall from the west.

Case II: Egmont Key.

Case III: Sarasota Case IV: Tarpon Springs

Arrow: landfall time

1. 5 m/s (10 knot)

2. 10 m/s ( 20 knot)

3. 2.5 m/s ( 5 knot)

Category 2 storm making landfall at Indian Rocks Beach from the west with speeds of

IRB landfall from the west withtranslation speeds of:

5 m/s,

10 m/s, and

2.5 m/s.

Arrow: landfall time

1. Category 2

2. Category 4

Storm making landfall at Indian Rocks Beach from the west with speeds of 5 m/s

30 Hour

OCG @ USF

Tampa

IRB landfall from the west at5 m/s for: category 2

category 4. Arrow: landfall time

The Surge in Tampa Bay Is Sensitive to:

1) the storm intensity;

2) the landfall location;

4) the direction of approach.

3) the speed of approach; and

Hurricane Charley Storm Surge Simulation

Big Carlos Pass

Ft. Myers

Sanibel Is.

Captiva

N. Pine Is.

Punta Gorda

E. side of CHW. side of CH

Courtesy of T. Liebermann

Summary1) Based on the lessons learned from Tampa Bay experiments we explain the relatively small H. Charley surge by virtue of:

• The approach direction from SW to NE and subsequent translation up the estuary.

• The rapid approach speed (16 knots).

• The small storm radius (10~20 km).

2) We account for the breach at North Captiva Island by the large across-barrier-island sea level gradient that occurred as the H. Charley passed by.

Acknowledgments

This work was supported by the Office of Naval Research, grants # N00014-98-1-0158 and N00014-02-1-0972 and by the U.S. Geological Survey, order # 4-SPSA-11920. Changsheng Chen (UMassD) kindly shared the FVCOM code, and Timothy Liebermann (SFWMD) kindly shared the CH merged bathymetric and topographic data set.