1. Extra-Tropical Storm Surge (ETSS 2.1)
Pre-Implementation Briefing
College Park, MD
Oct 30, 2015
Arthur Taylor and Huiqing Liu
Decision Support Branch

2. Sandy Supplemental Motivation
Future coastal flood and storm surge warnings likely require overland guidance
ETSS 1.5 (Oct 2014) and ESTOFS
Predict storm surge to the coastline but not overland
ETSS 2.0 (May 2015)
Overland “surge only” guidance for East Coast and Gulf of Mexico
Operationalize total water level post-processed guidance
ETSS 2.1 (Nov 2015)
Overland “surge and tide” guidance for East Coast and Gulf of Mexico
AK Priority: Resolve Bering Strait problem via a single Bering Beaufort Chukchi basin
Future –
P-ETSS 1.0 (Jun 2016)
Probabilistic Extra-Tropical overland Storm Surge and tide guidance
Extra-Tropical
Tropical
Storm Surge to Coastline
ETSS (1995 – 2014)
ESTOFS (2012 – )
ETSS 1.5 (2014 – 2015)
SPLASH (1972 – 1984)
Overland Storm Surge
ETSS 2.0 (May 2015)
No Real-Time Ensemble
No Climate Ensemble
SLOSH (1984 – )
P-Surge 1.0 (2008 – 2013)
MEOW/MOM (1986 – )
Overland Storm Surge + Gridded Tide
ETSS 2.1 (Nov 2015)
P-ETSS ( )
No Climate Ensemble
SLOSH + Tide (2012 – )
P-Surge 2.0 (2014 – 2015)
P-Surge 2.5 (May 2015)
No Climate Ensemble

3. ETSS 2.0 as of May 2015
Predicts overland inundation based on storm surge only
Runs 4 times a day using 0.5 degree Global Forecast System winds and pressure to create 96 hours of hourly guidance
Does so in the following areas …
Arctic AK (updated Jan 1996), Bering Sea (updated Oct 1998),
Gulf of AK (updated Apr 2008), East Coast (updated Feb 2009),
Gulf of MX (updated Jan 2011), West Coast (updated Feb 2011)
Based on the SLOSH model, but is intended for Extra-Tropical storms due to the wind forcing
Does not account for Tides, Waves, or River Flow

4. ETSS 2.1 Objectives
Overland Guidance from Extra-Tropical Surge and Tide
37 tidal constituents from ADCIRC’s EC-2014 (East Coast and Gulf of Mexico)
13 tidal constituents from Oregon State University's TPXO Global Tidal model (West Coast and Alaska)
Provide 625 m resolution output (vs 2.5 km)
BBC (Bering Beaufort Chukchi Seas) basin
Update 20 year old bathymetry data and incorporate topography data
Allow water to flow through the Bering Strait. Previously ETSS used two non-communicating basins on either side of the Strait.
Bug fixes
Merging Methods for East Coast and Gulf of Mexico
Correct SHEF products to use MLLW (rather than MHHW)

5. Bug Fix – Merging Methods 2012-Sandy Adv 27 (Surge only)
ETSS 2.0 (EX2 backup; smaller NY3 mask)
Red=NY3; Purple=EX2; Black=2.5km CONUS
ETSS 2.1 (EX2 ignored; larger NY3 mask) Red=NY3; Purple=EX2; Black=2.5km CONUS

6. Objective 1 Surge Only vs Surge + Tide (at 2.5 km)
ETSS 2.1 Surge Only 2.5 km inundation for 2012-Sandy (Blue is field verified)
ETSS 2.1 Surge + Tide 2.5 km inundation for 2012-Sandy (Blue is field verified)

7. Objective 1 Surge Only vs Surge + Tide (at 625 m)
ETSS 2.1 Surge Only 625 m inundation for 2012-Sandy (Blue is field verified)
ETSS 2.1 Surge + Tide 625 m inundation for 2012-Sandy (Blue is field verified)

8. Impact of Output Resolution on Inundation Extent
ETSS 2.1 Surge + Tide 2.5 km inundation for 2012-Sandy (Blue is field verified)
ETSS 2.1 Surge + Tide 625 m inundation for 2012-Sandy (Blue is field verified)

9. ETSS 2.1 Inundation Improvements
ETSS 2.0 Surge Only 2.5 km inundation for 2012-Sandy (Blue is field verified)
ETSS 2.1 Surge + Tide 625 m inundation for 2012-Sandy (Blue is field verified)

10. Room for Improvement Gridded vs Parametric and Native Res
ETSS 2.1 Surge + Tide 625 m inundation for 2012-Sandy (Blue is field verified)
SLOSH Surge + Tide native res. inundation for 2012-Sandy (Blue is field verified)

11. Objective 2: Opening the Bering Strait BBC (Bering, Beaufort, Chukchi Seas)
ETSS 2.1 (Oct 2015)
BBC (Green) replacing
OTZ (Purple)
NOM (Blue)
Future Goal (beyond Jun 2016)
Five (or more) nested higher resolution overland grids

12. Impact - Surge Only Forecast 0-h (06Z Oct 16)
Surge values start out the same

13. Impact - Surge Only Forecast 12-h (18Z Oct 16)
After 12 hours there are “minor” differences
Bering Strait and North West Bering Sea

14. Impact - Surge Only Forecast 24-h (06Z Oct 17)
After 24 hours there are “significant” differences
Cause: ETSS 2.0 uses OTZ and NOM basins which have a common boundary (at the Bering Strait), but information is not shared

15. Impact - Surge Only Forecast 36-h (18Z Oct 17)
After 36 hours the differences continue to spread
Most of Bering Sea is impacted
Very strong changes on “North Slope”
Red Dog Dock key observation point

16. Impact - Surge Only Forecast 48-h (06Z Oct 18)
After 48 hours the differences continue to spread

17. Statistical Analysis How to Determine Historic Events?
Obs. at Nome (example), Prudhoe, and Red Dog Dock from 2006 to 2014
Human Impact: Observation above Ground (MHHW) > Child height (3 feet)
3 feet MHHW is 4.52 feet MLLW for Nome
Surge Impact: Observation – Tide (aka Surge Only) > 4 feet

18. Storms Used to Validate the Model 15 for Human, 2 for Surge, 2 Omitted
Storm ID
Year
Forecast Start Time
96 hour period (6 hour projection) over which
RMSE, PAE is calculated
2006-A
2006
FEB 12 – 15 (00, 06, 12, 18z)
FEB 12 01z – FEB 16 00z
2006-B
OCT 15 – 18 (00, 06, 12, 18z)
OCT 15 01z – OCT 19 00z
2007-A
2007
JAN 29 – FEB 1 (00, 06, 12, 18z)
JAN 29 01z – FEB 2 00z
2007-B
SEP 9 – 12 (00, 06, 12, 18z)
SEP 9 01z – SEP 13 00z
2007-C
NOV 28 – DEC 1 (00, 06, 12, 18z)
NOV 28 01z – DEC 2 00z
2009-A
2009
MAR 4 – 7 (00, 06, 12, 18z)
MAR 4 01z – MAR 8 00z
2009-B
OCT 10 – 13 (00, 06, 12, 18z)
OCT 10 01z – OCT 14 00z
2009-C
DEC 5 – DEC 8 (00, 06, 12, 18z)
DEC 5 01z – DEC 9 00z
2010-A
2010
APR 10 – 13 (00, 06, 12, 18z)
APR 10 01z – APR 14 00z
2010-B
AUG 14 – 17 (00, 06, 12, 18z)
AUG 14 01z – AUG 18 00z
2011-A
2011
FEB 23 – 26 (00, 06, 12, 18z)
FEB 23 01z – FEB 27 00z
2011-B
NOV 8 (12, 18z)
NOV 9 – 11 (00, 06, 12, 18z)
NOV 12 (00, 06z)
NOV 8 13z – NOV 12 12z
2011-C
DEC 3 – DEC 6 (00, 06, 12, 18z)
DEC 3 01z – DEC 7 00z
2012-A
2012
SEP 4 – 7 (00, 06, 12, 18z)
SEP 4 01z – SEP 8 00z
2012-B
OCT 4 (12, 18z)
OCT 5 – 7 (00, 06, 12, 18z)
OCT 8 (00, 06z)
OCT 4 13z – OCT 8 12z
2013-A
2013
JUN 30 – JUL 3 (00, 06, 12, 18z)
JUN 30 01z – JUL 4 00z
2013-B
NOV13 – NOV16 (00, 06,12,18z)
NOV 13 01z – NOV 17 00z
2014-A
2014
OCT 25 – 28 (00, 06, 12, 18z)
OCT 25 01z – OCT 29 00z
2014-B
NOV 9 – 12 (00, 06, 12, 18z)
NOV 9 01z – OCT 13 00z

19. Mean RMSE and Peak Surge at 3 stations for 17 cases

20. Overall Model Skill ETSS 2.0 ETSS 2.1 ETSS 2.0 ETSS 2.1 PAE (feet)
RMSE
(feet)
2006A
2006 B
2007 A
2007 B
2007 C
2009 A
2009 B
2009 C
2010 A
2010 B
2011 A
2011 B
2011 C
2012 B
2013 B
2014 A
2014 B
ETSS 2.0
0.91
0.81
0.96
0.86
0.78
0.89
0.77
1.27
0.74
1.82
1.01
0.84
1.28
1.20
1.04
0.94
ETSS 2.1
0.80
0.70
0.82
0.69
0.64
0.99
0.68
1.46
0.59
1.05
0.98
0.92
New wind Drag
0.62
0.57
0.75
0.46
0.66
0.56
0.79
0.67
0.49
1.11
0.87
PAE
(feet)
2006A
2006 B
2007 A
2007 B
2007 C
2009 A
2009 B
2009 C
2010 A
2010 B
2011 A
2011 B
2011 C
2012 B
2013 B
2014 A
2014 B
ETSS 2.0
1.31
1.42
0.97
0.64
1.52
1.11
1.37
1.34
0.53
3.08
1.92
0.78
1.72
1.56
1.44
1.21
ETSS 2.1
1.22
0.76
0.91
0.92
1.30
0.38
2.45
1.65
0.58
1.45
1.13
0.94
New wind Drag
0.45
0.72
0.79
0.41
0.52
0.69
0.80
0.31
1.28
0.95
0.18
1.33
0.82

21. ETSS 2.1 Should we Implement?
Overland Guidance from Extra-Tropical Surge and Tide
625 m resolution East Coast and Gulf of Mexico
2.5 km resolution West Coast (and East Coast, Gulf of Mexico)
3.0 km resolution Alaska
BBC (Bering Beaufort Chukchi Seas) basin
Allows water to flow through the Bering Strait
Avoids erroneous boundary influences
Significantly improves the forecasts at the 3 observation sites for the 17 critical storms from 2006 to 2014
Bug fixes
Merging Methods for East Coast and Gulf of Mexico
Correct SHEF products to use MLLW (rather than MHHW)

22. Combined Impact of Sandy Supplemental Improvements
ETSS 1.5 Surge Only 2.5 km to coast for 2012-Sandy (Blue is field verified)
ETSS 2.1 Surge + Tide 625 m inundation for 2012-Sandy (Blue is field verified)

23. Backup

24. Surge Only Forecast 60-h (18Z Oct 18)
After 60 hours the differences continue to spread

25. Surge Only Forecast 72-h (06Z Oct 19)
After 72 hours the differences continue to spread

26. Surge Only Forecast 84-h (18Z Oct 19)
After 84 hours the differences continue to spread

27. Surge Only Forecast 96-h (06Z Oct 20)
After 96 hours the differences continue to spread

28. Tide Validation New Bering Sea (eBBC)
# station
RMSE
(feet) 7
0.36

29. Tide Validation Gulf of Alaska (eGOA)
# station
RMSE
(feet) 19
1.58

30. Tide Validation West Coast (eWC2)
# station
RMSE
(feet) 34
0.92