Local Storm Surge Considerations. Al Sandrik Warning Coordination Meteorologist National Weather Service Office Jacksonville, Florida

Transcription

1 Local Storm Surge Considerations Al Sandrik Warning Coordination Meteorologist National Weather Service Office Jacksonville, Florida

2 SLOSH Display Program

3 Some Definitions: Astronomical Tide: The daily variation in sea level due to the gravitational influence of the Son and Moon. STORM SURGE is an abnormal rise of water generated by a storm, over and above the predicted astronomical tide. Jelesnanski, Chen & Shaffer; SLOSH; NOAA T.R. NWS48 STORM TIDE is the total water level, above a datum, generated by a storm. Astronomical Tide + Storm Surge = Storm Tide (Astronomical Tide) 3 + (Storm Surge) 9 = (Storm Tide) 12 (Astronomical Tide) -3 + (Storm Surge) 9 = (Storm Tide) 6 But these simple examples may not tell the entire story on how storm tide reacts!

4 Astronomical Tides are an important consideration!

5 Astronomical Tides are a very important consideration!

6 Tide, Storm Surge and Storm Tide! Hurricane "Dora" Fernandina Beach Astronomical Tide 9/11-12/ :00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 Friday, September 11, 1964 Saturday, September 12, 1964 Astro

7 Tide, Storm Surge and Storm Tide! Peak Storm Surge Hurricane "Dora" Fernandina Beach Storm Surge 9/11-12/ :00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 Friday, September 11, 1964 Saturday, September 12, 1964 Surge

8 Tide, Storm Surge and Storm Tide! Primary Peak Storm Tide Secondary Peak Storm Tide Hurricane "Dora" Fernandina Beach Storm Tide 9/11-12/ :00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 Friday, September 11, 1964 Saturday, September 12, 1964 Storm Tide

9 Tide, Storm Surge and Storm Tide! Peak Storm Tide 7 Hours before peak storm surge! Peak Storm Surge Hurricane "Dora" Fernandina Beach Total Tides 9/11-12/1964 Secondary Peak Storm Tide 3 hours AFTER peak storm Surge! :00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 Friday, September 11, 1964 Saturday, September 12, 1964 Surge Astro Storm Tide

10 ALABAMA FLORIDA MISSISSIPPI Mobile Baldwin Escambia Santa Rosa Okaloosa Walton Hancock HarrisonJackson Bay ENVELOPE OF HIGH WATER (EOHW)

11 ALABAMA FLORIDA MISSISSIPPI Mobile Baldwin Escambia Santa Rosa Okaloosa Walton Hancock HarrisonJackson Bay NORTHERLY TRACKS

12 ALABAMA FLORIDA MISSISSIPPI Mobile Baldwin Escambia Santa Rosa Okaloosa Walton Hancock HarrisonJackson Bay MAXIMUM ENVELOPE OF WATER (MEOW)

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14 Maximum Envelope Of Water (MEOW) A number of Parallel SLOSH runs with the same Intensity, Track and Speed are run for a Basin. The only difference is that each run is done at some distance to the left or right of the main Track (usually in the center of the grid). Each component run derives a Storm Surge value for each individual grid cell if it is flooded or indicates Dry if not. Example: #1-5.2 #2-6.3 #3-4.2 #4-5.8 #5 Dry In this case the MEOW for this cell is 6.3 We do not know which run generated the MEOW for a particular cell It is entirely possible that the MEOW values for adjacent cells may have come from completely different runs!!!

15 A MEOW Example JAX Cat 4 WNW 15 MPH

16 Four MEOW runs with only the direction of storm motion changed (Cat 4; 15 mph SOA)

17 Maximum Of Maximums - MOM

18 MEOW MOM

19 Which run would represent the MOM for a Category 4 storm based on these MEOWs?

20 So how were these MOM s Derived? 11 Storm Motion Directions (WSW( WSW to E + Parallel to the coast) 3 Speeds Of Advance (SOA) for each direction (5( 5 mph, 15 mph, 25 mph) 12 runs for each SOA and Direction pairs (i.e.( i.e. 12 runs of WNW, 15 mph, Cat 4) 4 12 x 11 x 3 = 396 individual runs to arrive at a single Maximum value in each cell. This single Maximum value is the MOM for that Category in that particular cell

21 Hurricane Evacuation Studies

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23 Evacuation Zones 1. Delineated by major geographic features 2. Conform to existing political or demographic boundaries

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25 Individual Grid Barrier Stair Step Rise Water Surface above a square Transport Points Water Depth above a square Surge Points DATUM Dry and wetted grid squares. The squares are two-dimensional stair steps.

26 A Cross Section of a Cell Cell Water Depth = 7.0 B Flooded Dry NGVD

27 A Cross Section of a Cell Cell Water Depth = DRY B Flooded Dry NGVD

28 Let s look at several adjacent cells Lets say a hurricane makes landfall with a storm tide of 8 feet NGVD 15 DRY Open Creek Elem School 10 Open Creek Avg Elev 12 NGVD Avg Elev 7 NGVD Avg Elev 4 NGVD Cell avg water depth DRY Cell avg water depth 1 Cell avg water depth 4 5 A1A NGVD

29 Some general rules of thumb when looking at your coast s s topography and bathometry: 1. Concave portions of a coast will USUALLY hold more storm surge/tide than convex portions of coast. In plan English, all things being equal, a bay or estuary will experience higher storm surge/tide than a bulging coast or a point. 2. Shallow shelf waters will USUALLY allow a higher storm surge/tide to build up than deeper shelf waters. 3. Conversely coasts with shallow shelf waters will USUALLY experience less wave action than coasts with deeper shelf waters. 4. Choke points MAY experience greater storm surge/tide than surrounding areas. i.e. Rivers, canals, constricted channels. 5. Inland bodies of water can experience a sloshing or sieche effect, Lake Okeechobee and the St. Johns River are examples in Florida. 6. All of these are generalizations and in a real world event much is dependant upon the actual storm track (angle of incidence to the coast), speed of forward motion, size of the storm s s wind envelope, and radius of maximum winds. This is were your local WFO comes in!

30 Two meteorologically equivalent category five events but occurring in different portions of the Florida coast! Concave Coast Shallow Water Convex Coast Deep Water

31 Choke Points Houston Ship Channel

32 Choke Points 11.6

33 Look at where water piles up in bays

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36 Look At how the water piles up in the Estuary System!

37 Inland Bodies of Water Watch the St. Johns River From Orange Park to Downtown Jacksonville Graphic by Al Sandrik NWS WFO Jacksonville

38 Questions?