Roll or Arcus Cloud

Supercell Thunderstorms

Storm split 1

Storm split 3

Storm Split 2

Squall Lines

Bow Echos

Often Associated with Strong Straight Line Winds Known as

“Derechos”• Can reach 100-150 mph

• http://www.youtube.com/watch?v=EGJmOeDEBtw

• Great Derecho Website:

http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm

Climatology (Events over 1980-2001

High Resolution Numerical Prediction of Convection

Explicit Convective Prediction

• Requires high resolution (4km or less grid spacing)

• Requires high-resolution analysis of current situation, using radar, surface observations and all other assets.

• NCAR (WRF model) and CAPS (Oklahoma, ARPS model) are two leading efforts.

Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX)Using the WRF Model

Goal: Study the lifecycles of mesoscale convective vortices and bow echoes in and around the St. Louis MO area

10 km WRF forecast domain4 km WRF forecast domain

Field program conducted 20 May – 6 July 2003

Real-time WRF 4 km BAMEX Forecast

Composite NEXRAD RadarReflectivity forecast

Initialized 00 UTC 9 June 03

Real-time WRF 4 km BAMEX Forecast

Composite NEXRAD Radar

4 km BAMEX forecast 36 h Reflectivity

4 km BAMEX forecast 12 h Reflectivity

Valid 6/10/03 12Z

27h WRF BAMEX Forecast

Valid 6/10/03 03Z

4 km Max Reflectivity 10 km Max Reflectivity

30h WRF BAMEX Forecast

Valid 6/10/03 06Z

4 km Max Reflectivity 10 km Max Reflectivity

Real-time WRF 4 km BAMEX Forecast

Initialized 00 UTC 10 June 03

Reflectivity forecast Composite NEXRAD Radar

Real-time 12 h WRF Reflectivity Forecast

Composite NEXRAD Radar

4 km BAMEX forecast

Valid 6/10/03 12Z

10 km BAMEX forecast

22 km CONUS forecast

Composite NEXRAD RadarReflectivity forecast

Real-time WRF 4 km BAMEX Forecast

Initialized 00 UTC 30 May 03

Real-time WRF 4 km BAMEX Forecast

Composite NEXRAD Radar23 h Reflectivity Forecast

Line ofSupercells

Valid 5/30/03 23Z

Realtime WRF 4 km BAMEX Forecast

Composite NEXRAD Radar30 h Reflectivity Forecast

Squall line

6” hail 00Z

Valid 6/23/03 06Z

Real-time WRF 4 km BAMEX Forecast

Initialized 00 UTC 11 June 03

Reflectivity forecast Composite NEXRAD Radar

Realtime WRF 4 km BAMEX Forecast

Composite NEXRAD Radar30 h Reflectivity Forecast

Missed

Valid 6/12/03 06Z

Real-time WRF 4 km BAMEX Forecast

Initialized 00 UTC 24 May 03

Reflectivity forecast Composite NEXRAD Radar

Realtime WRF 4 km BAMEX Forecast

Composite NEXRAD RadarReflectivity Forecast

12 h

24 h

Squall line

Persists Dissipates

Initialized 5/24/03 00Z

Preliminary BAMEX Forecast Verification

(Done, Davis, and Weisman)

Mode for corresponding convective systems

For Convective Mode 2 or 3

Cases Observed

Yes No

CasesPredicted

61 25

16 21

Yes

No

Probability of detection (POD) = 79%

False alarm rate (FAR) = 29%

A High-Resolution Modeling Study of the 24 May 2002 Dryline Case during IHOP

(Xue and Martin 2006a,b MWR)

Goal: Understand exactly

WHEN, WHERE, HOW convection is initiated

Time and Location of Initiation(Loop time: 17UTC – 22 UTC)

Surface analysis

+ satellite images

From Wakimoto et al.(2006 MWR).

1900 2000

22002100

18 UTC May 24, 2002 I.C.3 km / 1km grid

Model Configurations

• ARPS model with full physics, including ice microphysics + soil model + PBL and TKE-SGS turbulence

1200 UTC 1800 UTC 0006 UTC

1km3km

CI ~ 2000UTC

0000 UTC

ADAS ADAS

t=3h, 2100 UTC

sfc. winds, qv, and composite reflectivity

t=4h, 2200 UTC

t=5h, 2300 UTC

t=3h, 2100 UTC

t=2h t=2h 15min t=2h 30min t=2h 45min

A A A

B BB

C C

C

B

A

2000 UTC 2015 UTC 2030 UTC 2045 UTC