Use of Mesoscale Models for Analysis of High Impact Weather Events

Alfred M. Klausmann, CCM

Atmospheric Studies Group

Objectives

• Estimate peak wind speed within New Orleans during passage of hurricane Katrina • Use this information to determine if this could have caused wall damage to industrial buildings

Hurricane Katrina Track and Maximum Sustained Winds .

Hurricane KatrinaTrack and Maximum Sustained Winds

500 92.W

90.W

88.W

86.W

84.W

400 82.W

300 0830 0000 UTC Max wind: 25 m/s 32.N

200 100 0829 1800 UTC Max wind: 41 m/s 30.N

0 -100 -200 -300 0829 1200 UTC Max wind: 57 m/s 0829 0600 UTC Max wind: 64 m/s 0829 0000 UTC Max wind: 72 m/s 28.N

26.N

-400 0828 1200 UTC Max wind: 74 m/s -500 -600 .

-700 24.N

0827 1200 UTC Max wind: 51 m/s -300 -200 -100 0 LCC Origin: 30.00N, 90.00W

Matching Parallels: 20.00N, 40.00N

Datum: NWS-84 100 200 300 LCC East (km) 400 500 600 700 800 900 .

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MM5 Grid Configuration

• Four grids at 54, 18, 6, and 2 km resolution (Grids A, B, C, and D) • All domains are two-way interactive. The 2 km domain is movable.

• 32 vertical levels

Hurricane Katrina MM5 Grid Nesting

Hurricane Katrina MM5 Grid Nesting

2000 Grid A 1500 1000 500 0 -500 -1000 Grid B Grid C 29/1200UTC 28/1200UTC 26/0000UTC -1500 -2000 -2000 -1500 -1000 -500 0 500 LCC East (km) 1000 1500 2000

MM5 Physics

• Betts-Miller Cumulus parameterization implemented on the 54 and 18 km domains. Convection modeled explicitly on the 6 and 2 km domains.

• Blackadar Planetary Boundary Layer scheme used • Goddard Mixed-Phase Microphysics used • MM5 Cloud-Radiation scheme used

Model Initialization and Input Data

• MM5 initialized on August 27, 2005 at 1200 UTC. Model run out to 60 hours. The 2 km resolution movable nest was initialized at 36 hours into the simulation (0000 UTC on August 28, 2005).

• NCEP Final Analysis global 1 degree x 1 degree meteorological fields provide the initial and lateral boundary conditions • NCEP RTG 0.5x0.5 degree sea surface temperature data is used. • Hurricane Katrina initialized using the MM5 Tropical Cyclone Bogussing scheme and the NCEP-Tropical Prediction Center best track data.

Tropical Cyclone Bogussing Scheme

• Inserts vortex into the global analysis fields. Objective is to improve the representation of the hurricane over what it possible with coarser global data.

• On Grid A (54 km grid) the radius of maximum wind is set at 90 km.

• On finer resolution grids radius of maximum wind is set at 60 km which is based on GOES infrared imagery and Microwave satellite images from Polar orbiting satellites.

• Maximum wind speed set at 51 m/s (100 knots).

Four Dimensional Data Assimilation

• Used FDDA on the outer coarse grid only.

• Without FDDA the simulated track of Katrina was about 30 km to far to the west.

• Sensitivity tests showed that using nudging parameters for wind, temperature and moisture that were 50 percent of their default values yielded the best results.

• The MM5 track was very close to the NCEP-TPC track data.

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Surface wind vectors and isotachs on August 29, 2005 at 0600 UTC 0 -50 -100 -150 -200 30.N

70 65 60 55 50 29.N

45 40 35 30 25 20 15 10 5 0 Wind Speed (m/s) -100 -50 0 LCC Origin: 30.00N, 90.00W

Matching Parallels: 20.00N, 40.00N

Datum: NWS-84 50 LCC East (km) 100 150 200 Reference Vectors Wind Speed In m/s 20 .

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Surface wind vectors and isotachs on August 29, 2005 at 1200 UTC

(b) 1200 UTC August 29, 2005

88.W

90.W

89.W

150

1800 UTC

31.N

100 50 0 -50 -100

1200 UTC

30.N

50 45 40 35 70 65 60 57 55 30 25 20 15 10 5 0 29.N

Wind Speed (m/s) .

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-150 -100 -50 0 LCC Origin: 30.00N, 90.00W

Matching Parallels: 20.00N, 40.00N

Datum: NWS-84 50 LCC East (km) 100 150 200 Reference Vectors Wind Speed In m/s 20 .

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Surface wind vectors and isotachs on August 29, 2005 at 1300 UTC 90.W

89.W

88.W

150 100 50 0 -50 -100 31.N

70 65 60 55 50 45 40 30.N

35 30 25 20 15 10 5 0 29.N

Wind Speed (m/s) .

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-150 -100 -50 0 LCC Origin: 30.00N, 90.00W

Matching Parallels: 20.00N, 40.00N

Datum: NWS-84 50 LCC East (km) 100 150 200 Reference Vectors Wind Speed In m/s 20 .

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Surface wind vectors and isotachs on August 29, 2005 at 1400 UTC 88.W

90.W

89.W

150 100 50 0 -50 -100 31.N

30.N

45 40 35 30 70 65 60 55 50 25 20 15 10 5 0 29.N

Wind Speed (m/s) .

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-150 -100 -50 0 LCC Origin: 30.00N, 90.00W

Matching Parallels: 20.00N, 40.00N

Datum: NWS-84 50 LCC East (km) 100 150 200 Reference Vectors Wind Speed In m/s 20 .

MM5 Wind Speed Vs Height Over New Orleans

1100 1000 900 800 700 600 500 400 300 200 100 0 30 35 40 20050829 1300 UTC 45 50 55

Wind Speed (m/s)

60 65 70

1100

MM5 Wind Speed Vs Height Near Pass Christian Beach, MS

1000 900 800 700 600 500 400 300 200 100 0 30 35 40 45 50 55 60

Wind Speed (m/s)

65 70 75 80 M M 5 20050829 1300 UTC M M 5 20050829 1400 UTC Dro pso nde M M 5 20050829 1500 UTC MM5 Wind Speed Vs Height Near Pass Christian, MS (see Henning, 2006)

Mean Wind Speed Profiles All Storms

Mean wind profile

(Obtained from National Center’s for Environmental Prediction Tropical Prediction Center)

Calculated wind-induced pressure contours from FLUENT Model using MM5 peak winds

Pressure Contours - 60 m/s WNW

Pressure Contours – 60 m/s WNW

Doors Closed Doors Open

Summary

• Successfully applied the MM5 model to reasonably reproduce the core surface wind field of Hurricane Katrina during landfall.

• Used this information to obtain an estimate of peak surface wind speeds in the New Orleans area.

• Used the MM5 derived wind speed estimates as input to the FLUENT CFD model and demonstrated that wind was the cause of damage to industrial buildings.

• MM5 proved to be a valuable post-event analysis tool to provide high-resolution data for extreme weather events.

• This application of mesoscale models could also be expanded to include other meteorological parameters (e.g. precipitation).