A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak
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A Multiscale Analysis of the 23-24 November 2004 Southeast United States Tornado Outbreak. Alicia C. Wasula. Event Summary. 23/1700 UTC – 24/1300 UTC (nocturnal) 80 Tornadoes (17 F2 or greater) 3 Fatalities / 38 Injuries 45% tornadoes close to Gulf coast (south of 32 N). Motivation.

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A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

A Multiscale Analysis of the 23-24 November 2004 Southeast United States Tornado Outbreak

Alicia C. Wasula


Event summary
Event Summary United States Tornado Outbreak

  • 23/1700 UTC – 24/1300 UTC (nocturnal)

  • 80 Tornadoes (17 F2 or greater)

  • 3 Fatalities / 38 Injuries

  • 45% tornadoes close to Gulf coast (south of 32 N)


Motivation
Motivation United States Tornado Outbreak

  • Examine tornado episode from synoptic/mesoscale perspective to look for similarities/differences to composite Gulf coast tornado episode


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE vs. Shear for Cold Season Tornado Cases United States Tornado Outbreak

0-2 km positive mean shear (x 10-3 s-1)

Convective Available Potential Energy (CAPE, J/kg)

Johns et al. 1993


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE vs. Shear for Warm Season Tornado Cases United States Tornado Outbreak

0-2 km positive mean shear (x 10-3 s-1)

Convective Available Potential Energy (CAPE, J/kg)

Johns et al. 1993


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

Tornado Episode Composites United States Tornado Outbreak

  • NCEP/NCAR 2.5x 2.5 Reanalysis dataset

  • All tornado episodes 1950-2001

  • ‘Episode-relative’ composite

  • Grouped by start time: 0000-0600, 0600-1200, 1200-1800, 1800-0000 UTC

  • Will show 0600-1200 UTC only


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

200 hPa height (m), isotachs (m s United States Tornado Outbreak-1)

500 hPa hgt (m), avor. (x 10-5 s-1), vort. adv. (x 10-10 s-2)


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

1000 hPa height (m), 1000-500 thck. (dam), 700 hPa RH (%) United States Tornado Outbreak

850 hPa hgt (m), temp (C), temp. adv. (x 10-5 C s-1)


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

850 hPa winds, United States Tornado Outbreake (K), 850-500 lapse rate (C)

700 hPa height (m), vertical motion (x 10-3 hPa s-1)


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

Summary: Composites United States Tornado Outbreak

  • Strong signal in spite of large sample size:

    • ULJ entrance region at 200 hPa

    • Vigorous upstream trough at 500 hPa

    • Southwesterly LLJ at 850 hPa

    • Low-level e ridge

  • Surface composites show 1st tornado occurs:

    • At strongest T

    • On northern edge of moisture surge/southerly flow

    • Dew point anomalies > +8 C


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

Case Study: United States Tornado Outbreak24 November 2004


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

http://www.spc.noaa.gov United States Tornado Outbreak


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

22 November 2004 0000 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

22 November 2004 1200 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

23 November 2004 0000 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

23 November 2004 1200 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

23 November 2004 1800 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

24 November 2004 0000 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

24 November 2004 0600 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

SLP United States Tornado Outbreak, 1000-500 THCK

500 hPa HGHT, AVOR

24 November 2004 1200 UTC

850 hPa HGHT, e, ISOTACHS

200 hPa HGHT, ISOTACHS


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 1847 J/kg United States Tornado Outbreak

LI -7

0-6 km shear 38 kt

0-2 km shear 18 kt

SWEAT 400

JAN

23/2100 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 1648 J/kg United States Tornado Outbreak

LI -6

0-6 km shear 58 kt

0-2 km shear 16 kt

SWEAT 464

JAN

24/0000 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 81 J/kg United States Tornado Outbreak

LI 3

0-6 km shear 39 kt

0-2 km shear 22 kt

SWEAT 225

JAN

24/1200 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 1794 J/kg United States Tornado Outbreak

LI -6

0-6 km shear 54 kt

0-2 km shear 4 kt

SWEAT 279

LIX

24/0000 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 2087 J/kg United States Tornado Outbreak

LI -7

0-6 km shear 40 kt

0-2 km shear 12 kt

SWEAT 332

LIX

24/0600 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 2986 J/kg United States Tornado Outbreak

LI -10

0-6 km shear 32 kt

0-2 km shear 10 kt

SWEAT 513

LCH

23/1800 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

CAPE 2412 J/kg United States Tornado Outbreak

LI -8

0-6 km shear 42 kt

0-2 km shear 9 kt

SWEAT 353

LCH

24/0000 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

Surface Analysis United States Tornado Outbreak

24 November 2004

0000 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

http://www.spc.noaa.gov United States Tornado Outbreak


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

http://www.spc.noaa.gov United States Tornado Outbreak


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

Surface Analysis United States Tornado Outbreak

24 November 2004

0600 UTC


A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

http://www.spc.noaa.gov United States Tornado Outbreak




A multiscale analysis of the 23 24 november 2004 southeast united states tornado outbreak

Surface Analysis

24 November 2004

1200 UTC



Conclusions
Conclusions

  • Tornado episode occurred:

    • In presence of strong synoptic-scale forcing for ascent (in warm sector)

    • LLJ strength increased overnight

    • Surface winds stayed south or southeast as surface low rapidly deepened to the north

    • Ample moisture and instability


Conclusions1
Conclusions

  • Case study shows similarities to composite tornado episode

    • Strong shear/ULJ/LLJ

    • Deepening surface cyclone

    • Ample low-level moisture (esp. close to coast)

    • Surface winds ‘back’ with time ahead of surface low

  • Difference:

    • Mesoscale thermal gradient?


Future work
Future Work

  • Question:

    • Did isallobaric effects help to keep flow in warm sector southerly/southeasterly and allow warm moist Gulf air to remain in place close to coast?

  • Why did LLJ increase in strength so rapidly?

    • Dynamically driven?