Forecasting Convective Mode and Severity

Forecasting Convective Mode and Severity

Mark F. BrittNational Weather Service

St. Louis, MO

Why Am I Here?A Basic Review of Severe Thunderstorm Forecasting.

Examine moisture return,instability, and shear calculations.Examine how the amount and distribution of instability, vertical shear, and forcing interact to determine cell type, convective mode (linear or discrete), and coverage.Determine what type(s) of severe weather to expect for a given environment.

Using NumbersThere are NO “magic” numbers or thresholds. They are merely guidelines.Best to look where several key parameters overlap instead of depending on one index.You should look at skew-Ts and hodographs (observed and forecast) to better understand what the numbers mean.Increase your situation awareness by using near storm environment data, but do not use it solely to make warning decisions.

Objective Analysis

Available on AWIPS using MSAS, LAPS, or RUC40 analysis (Thompson et al. (2003) found RUC analysis is a reasonable proxy to observed soundings in supercell environments, except they are too cool and dry at the surface.)Or, the SPC Mesoanalysis Page:

http://www.spc.noaa.gov/exper/mesoanalysis/

1. Displays a national and seven movable regions that is usually available by 20 minutes past each hour

2. Displays a robust set of hourly objective analysis datasets using the latest surface observations and upper air analysis from the RUC. Depicted contours highlight important “thresholds”.

Ingredients for Deep, Moist Convection

Moisture: (Gulf of Mexico, evapotranspiration)

Instability: (Steep lapse rates either from the Elevated Mixed Layer off the Rockies, or large scale “dry” ascent ahead of a trough.)

Forcing: (Surface frontal boundary, convective outflow, 900-800mb moisture convergence at nose of nocturnal low level jet, orographic lift over the eastern Ozarks)

Moisture Return

Look for rapid moisture advection from the Gulf of Mexico in strong pressure gradients ahead of a strong storm system.

Ridging associated with surface highs in or near the Gulf can inhibit moisture return.

Lanicci and Warner (1991)

Assessing Instability

Which is best?SBCAPEMLCAPEMUCAPE

SBCAPE: Surface Based. Uses the surface temperature and dew point. Will show large diurnal swings. Can give significant overestimates (an order of magnitude) in cases of shallow moisture and underestimates in cases of elevated convection.

From Peter Banacos, SPC (2003)

MLCAPE: Mean Layer. Uses the mean temperature and mean mixing ratio in the lowest part of the atmosphere (SPC uses lowest 100 mb). Less variable in time and space, and more conservative than MUCAPE when lower atmosphere is not well mixed.


MUCAPE: Most Unstable Parcel. Uses most unstable parcel in lower atmosphere (SPC uses lowest 300mb). Helps with nocturnal or other types of elevated convection.


What Do I Do With This?

RUC MUCAPE -March 12, 2006 @ 17Z

?

What Do I Do With This?

NAM MUCAPE - March 12, 2006 @ 17Z

Surface Based Parcels

Strong tornado

outbreak over Missouri.

KSGF RAOB

March 12, 2006 @ 21Z

Surface Based Parcels

Violent tornado

outbreak over western Missouri.

KSGF RAOB

May 5th, 2003 @ 00Z

Elevated Based Parcels

Numerous Reports of Hailin Eastern NE/

Western IA

KOAX RAOB

May 4th, 2003@ 18Z

CAPE vs. Parcel SelectionApril 22, 2004

From Jon Davies Webpage

Surface Based CAPE

Mean Layer CAPE

April 22nd, 2004 @ 22Z

From Jon Davies Webpage (http://members.cox.net/jdavies1/)

How Tall is the CAPE?

How Tall is the CAPE?April 22nd, 2004


How Wide Is the CAPE?

Larger differences between parcel temperature and the environmental temperature means stronger updrafts that are less susceptible to entrainment.

Lapse Rates

Craven (2000) found in a study of 65 major tornado outbreaks that 6.7o C/km is a useful lower limit. He also found low shear environments that produce tornadoes have steeper lapse rates.Steep mid level lapse rates (850-500 mb) have more conditional instability and increased CAPE. Steep low level lapse rates (0-3km AGL) can give a better idea on how quickly convection will develop.

Mid Level Lapse Rates

Sat Morn – 12Z Sat Eve – 00Z

Sun Eve – 00ZSun Morn – 12Z

Mid

Lev

el L

apse

Rat

es

Assess Vertical Shear

Distribution of vertical shear will determine dominant thunderstorm type.

Can be determined using either:

Traditional fixed layers (0-6km bulk shear, 0-1km SRH)

“Effective” shear which accounts for sounding dependent inflow layer through CAPE and CIN constraints. (Large sample testing suggests that “effective layer” is best defined by CAPE >100 J kg-1 and CIN >-250 J kg-1 CIN. (Thompson 2007))

Low level curvature can determine if right-movers, left-movers, or both kinds of splits are favored.

Storm Type: Ordinary Cells

Dominant Type in Weak Shear Environments

Pulse Type Severe Storms.

Storm Type: Multicells

Moderate to strong shear is confined mainly to the lower levels (0 to 3 km AGL)

Organized Multicells

>40kt 0-6 km shear>30kt 700-500mb windDry (low theta-e) midlevel air (strong cold pool)Downshear SBCAPE maxSystem relative convergence acting downshear to enhance forward propagation

Storm Type: Supercells

A study of 440 supercells found that long lived supercells (those lasting >4 hrs) produce notably more F2–F5 tornadoes when compared with short-lived supercells, and a single long-lived supercell can also produce a substantial amount of nontornadic severe weather. (Bunkers, et al. 2006)

Deep Shear Magnitude0-6 km layer shear “thresholds”:• 40+ kts: if storms develop -- supercells are likely (provided

convective mode favors cellular activity)

• 30-40 kts: supercells also possible if environment is very or extremely unstable as storm can augment local shear (>5,000 J/kg (Burgess (2003))

• About 15-20 kts: shear needed for organized convection (multicell or supercell) with mid level winds at least 25 kt

Supercells become more probable as the effective bulk shear vector increases in magnitude through the range of > 25-40 kts. (SPC Mesoanalysis Page description)

Bunkers et al. 2006 found that long-lived supercells occur in environments with much stronger 0-8-km bulk wind shear ( > 50 kt) than that observedwith short-lived supercells.

While 0-6km shear is a good discriminator between cell types, it isn’t a good tornado forecast tool (Thompson et al, 2002).

0-6 km Shear Magnitude

0-6 km VECTOR SHEAR MAGNITUDE

20.218.8

13.9

5.1

31.8 31.1

20.4

14.3

24.522.1

15.1

7.8

18.315.6

12.0

3.6

29.227.3

17.7

11.0

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

sigtor (54) nontor (215) mrgl (15) nonsuper (75)

m s

-1Supercells

Non-Supercells

From Thompson et al (2002)

BRN Shear(Weisman and Klemp (1982), and Thompson (2000

&2002)BRN Shear is the vector difference between the density weighted mean winds in the lowest 6 km and the lowest 500 m above ground level. BRN shear can be a used as a good predictor of storm type and severity. BRN SHEAR

50

3120

3

111

94

46

19

70

47

31

7

42

2316

1

87

75

35

13

0

20

40

60

80

100

120

sigtor (54) nontor (215) mrgl (15) nonsuper (75)

m2 s

-2

Supercells

Non-Supercells


40 m2/s2

35 m2/s2

Supercell Composite Parameter (Thompson et al, 2003)

The Supercell Composite Parameter (SCP) is a multi-parameter index that includes 0-3 km SRH, CAPE, and BRN Shear. Each parameter is normalized to supercell “threshold” values.

SCP = (muCAPE/1000 J/kg) * (0-3km SRH/100 m^2/s^2) * (BRNShear/40m^2/s^2)

Computed every hour on the SPC Mesoanalysis Page.

March 12th, 2006 @ 03Z March 12th, 2006 @ 21Z

March 13th, 2006 @ 03Z

What Causes Supercell Type

Rasmussen and Straka (1998) found in an observational study of 43 isolated supercells that supercell type is much more dependent precipitation efficiency based on its ingestion of hydrometeors.

Classic Supercells

The real “value” of a CL supercell is that it appears to be the most efficient of the three types to produce significant tornadoes.

Can occur nearly anywhere in U.S. when NSE supports them.

High Precipitation (HP) Supercells

High Precipitation (HP) Supercells

Lower mid-level and anvil-relative flow.Interactions with other storms –

“seeding”, more storms can occur with weak caps.

Typically associated with weaker tornadoes, but can produce significant tornadoes (Plainfield IL).

More of a severe wind (Pakwash), hail, and flash flooding threat.

Are the more-common supercell type east of the Mississippi owing to NSE conditions there (weaker caps, etc.), and may be the most common type everywhere in the U.S.

Supercell DimensionsBurgess (2003)

Cone of Silence

Falcon CoFalcon Co Hurr. OpalHurr. Opal

“mini”“mini” “large”“large”“mini”“mini”

“high-topped”“high-topped” “low-topped”“low-topped”“low-topped”“low-topped”

Vert

ical

Dim

ensi

on

Vert

ical

Dim

ensi

on

Hori

zonta

lD

imensi

on

Hori

zonta

lD

imensi

on

Pond Bank PAPond Bank PA

Supercell MovementBunkers et al (2000)

A physically based, shear-relative, and Galilean invariant method based on 290 supercell hodographs.

Supercell MovementBunkers and Zeitler (2000)

There are some caveats to this method:

Stronger deep-layer vertical wind shear (0-6 km) leads to a stronger mesocyclone and thus to greater deviation from the mean wind.

Weaker mid-level storm-relative winds allow for a stronger cold pool, and thus a tendency for the supercell to move rapidly downshear.

Depth of thunderstorms need to be considered.

Supercell motion can be altered by wind shear from boundaries and orography.

It is surface based. (Thompson, et al., 2007)

Storm Coverage and ModeWhat’s the Problem?

Evans (2003) noted Strong Forcing Derechoes and discrete, significant tornadic supercells (F2-F5) can occur in similar environments.

Thompson and Mead (2006) found in a study of 223 storms over the southern Plains that the probability of significant tornadoes is four times greater with discrete convection over non-discrete.

Unfortunately, differences can be very subtle and difficult to diagnose operationally.

What Controls Storm Coverage?

(Thompson, 2004)Widespread coverage expected with:

Rich moisture influx and steep lapse ratesCombination of Q-G and mesoscale ascent

(Differential CVA and WAA with surface frontogenesis)

Little CIN (Everything goes up.)

Isolated (or no) storms with:Marginal moisture and lapse rates (weak CAPE)Neutral to subsident large-scale environment

(Rely on small-scale/shallow processes for initiation)

Large CIN (Confine storms to “strongly forced” or in areas of most persistent ascent)

Supercells or Squall Line?

Discrete Linearweaker Strength and Depth of

Forcingstronger and/or deeper

(or confined near boundary)

more Amount of CIN compared to Boundary Forcing

less

weaker Potential for Cold Pool greater

more perpendicular Shear Vector w.r.t. Boundary Orientation

more parallel

Bunkers et al. (2006) found in their study of 440 supercells that long lived variety (>4 hrs) tend to occur in medium forced* environments whereas strongly forced events caused more linear or mixed modes of convection.

*surface boundaries w/ horizontal temperature gradient of 2.5-5oC/100 km or 300mb jet max of 50-70kts

Initiating Boundary w.r.t. Deep Layer Flow

(Bluestein and Weisman, 2000; Dial and Racy, 2004; James et al., 2005)

Parallel: (lines dominate, with end supercells)45-60o: (discrete supercells, little storm interaction)90o: (colliding storm splits, but depends on storm

spacing and hodograph shape)

0-6 km shear across dryline, and storm motion faster than boundary motion

From Rich Thompson, SPC

Progressive TroughMay 4th 2003 Tornado Outbreak, Progressive Flow

Aloft

0-6 km shear across boundary, and storm motion faster than boundary motion

Progressive TroughMarch 12th 2006 Tornado Outbreak, Progressive

Flow Aloft

0-6 km shear largely parallel todryline, and storm motion slower than boundary motion

From Rich Thompson, SPC

High Amplitude Trough

April 6th 2001 Great Plains “High Risk” Squall Line

Sat Eve – 04Z

Sun Eve – 06ZSun Eve – 00Z

Dee

p S

hear

vs.

Bou

ndar

y O

rient

atio

n

Sun Aftn – 21Z

Derechoes or Tornadoes?Anvil SR Winds may show some discrimination (Evans

2003).

Surface Pressure Changes

1-2 hourly pressure changes help identify:

Mesolow /mesohigh couplets and boundaries

Concentrated fall/rise couplet enhance low- level convergence/shear by backing surface winds (enhancing tornado threat)

Clouds associated with surface pressure falls may be linked to a dynamical feature

Implications on thermal advection

Rise/Fall couplets may indicate severe wind threat in marginal CAPE environments

Tornado ParametersMesocyclonic Tornadoes

Low Level Shear Vector and Storm Relative Helicity

Low Level Thermodynamic Profile1. Height of LCL2. Height of LFC3. Low Level CAPE and CIN

Boundaries

Non-Mesocyclonic Tornadoes

0-1km Shear VectorBrooks and Craven (2002)

Supercells associated with significant tornadoes

Non-Tornadic

20 kts

15kts

Markowski et al (2002) states this is a measure of the amount of horizontal vorticity available near the earth’s surface.

The shear magnitude in the lowest 1 km discriminates well between tornadic and non-tornadic supercells, and is a good proxy for 0-1km helicity (Thompson et al, 2002).

Does not require knowledge of storm motion.

0-1km Shear Vector

March 13th, 2006 – 03Z

Monroe County F4

0-1km Storm Relative Helicity

0-1 km versus 0-3 km SRH (Observed motion)

106

51

172

91

317

264

396362

165

93

223

146

74

20

108

37

220

162

317

233

0

50

100

150

200

250

300

350

400

450

sigtor 0-1 km nontor 0-1 km sigtor 0-3 km nontor 0-3 km

m2 s

-2

Supercells associated with significant tornadoes

Non-Tornadic

Thompson et al (2002)

SRH can vary up to two orders of magnitude within 100km and 3 hrs.

No good threshold, but 100 m2/s2 is considered a good lower number with increasing threat as the numbers grow. Outbreaks 200-300 m2/s2. (Rasmussen and Blanchard, 1998 and Thompson et al, 2002).

Thompson (2007) found effective SRH discriminated sig-tor better than non-tor cases.


From Banacos (2003)

May 4th, 2003 @ 22Z

April 22nd, 2004 @ 23Z



March 13th, 2006 @ 03Z

Monroe County F4

Wind Shear

Conway, MO Profiler

Sun

day

Eve

ning

Base Reflectivity – 0040Z

Base Reflectivity - 0313Z

Base Reflectivity - 0142Z

Base Reflectivity – 0443Z

Hodograph KinksFour violent tornado events in central and northern Oklahoma have had hodograph kinks. Similar kinks have been observed in MO the fast few years. A pronounced kink with the 1.0-1.5 km AGL layer is where a transition from weak veering, strong speed shear with height to strong veering, weak speed shear.

SGF 3/13/2006-03Z

SGF 5/04/2003-20Z

Height of the LCL (Mean Layer)

Markowski (2000) speculates that lower LCL heights (< 1000m) mean high boundary layer RH and increased buoyancy in the RFD.

Davies (2006) studied 44 “high” (1,300-2,000m) LCL cases, but they had the other thermodynamic and kinematic factors (including sizeable total and 0-3km CAPE) that are very favorable for supercells.

MLLCL

848 870 979

13241322

18952036

3041

10041180

1339

1768

769 720 7721015

1149

15781732

2509

0

500

1000

1500

2000

2500

3000

3500

sigtor (54) weaktor (144) nontor (215) nonsuper (75)

m (A

GL)

Height of the MLLCL

From Brooks and Craven (2002)


Let’s Take a Look

ILX

5/11/2003 @ 00Z

Classic supercells which produced several strong

tornadoes.

Height of the LFCWhy is this important?

Lower LFC’s (below 2km or 750mb) have more instability above the LFC and less CIN above that higher LFC’s.Lower LFC’s require less lift for the parcel to reach convective initiation

In a study of over 300 soundings associated with supercells, most tornadoes are found with LFCs below ~6,600 ft, though may occur as high as ~7900 ft with large amounts of vertical shear. (Davies, 2002) Rasmussen and Blanchard (1998) found that 75% of tornadic classic supercell environments had CIN <25-50 J/kg) and 60% of nontornadic supercell environments had values greater than this

Let’s Take a Look

ILX

6/2/1999 @ 00Z

Several supercells, one producing a F3

tornado.

Let’s Take a Look

SGF

6/2/1999 @ 00Z

Several classic supercells along I-44, including a F3.

What About Boundaries?

Boundaries serve two important functions:

Local forcing mechanisms for convective initiation.

As a source of vorticity augmentation in mesocyclones.

Significant tornadoes usually require higher quantities of SRH than is normally provided. They often require augmentation from boundaries. (Markowski et al (1998a))

Forward Flank

Downdraft

Streamwise vorticity occurs along the boundaries of the FFD.

Parcels generally only acquire 0.001 s–1 shear because of small residence times.

For FFD boundaries to be the primary source of streamwise vorticity, it is speculated that the environment must be highly helical (i.e. SRH > 500 m2 s–2 or 0-10 km shear of ~100 kts per Markowski et al (1998b).

Outflow From External ThunderstormsRasmussen (2000)

“Cool” side of outflow

boundaries: Look for modified

outflow (>6 hrs old) where there’s sunshine and

growing CAPE (a.k.a. “cooked” outflow),

and surface dewpoints are

greater than the warm sector.

BoundariesMarkowski et. al.

(1998b)

Tornadic development

most likely from 10 km on warm

side of boundary to 30 km on cool side

of boundary.

Local Example

May 6, 2003

Local Example

April 21, 2002From of Fred Glass

Anvil Boundaries

Requires limited cloud coverage around periphery of storm.

May be more important than the FFD because of much long parcel residence times in the boundary depending on the inflow vector.

Preferred direction for longer parcel

residence times.

Significant Tornado Parameter (Thompson et al, 2003)

The Significant Tornado Parameter is a multi-parameter index that includes 0-6-km shear magnitude, 0-1km storm-relative helicity, 100-mb mean parcel CAPE, and 100-mb mean parcel LCL height.

STP =(mlCAPE/1000 J/kg) * ((2000 -mlLCL)/1500 m) * (SRH1/100 m^2/s^2) * (SHR6/20 m/s)

Computed every hour on the SPC Mesoanalysis Page.


May 4th, 2003


March 12th, 2006 – 03Z


March 13th, 2006 – 03Z

Non-Supercell Tornadoes

Typically associated with ordinary cells

No CIN

Steep low level lapse rates

Sharp boundary with low level vertical vorticity.

Rapidly developing CBs

Non-Supercell Tornadoes

From Wakimoto and Wilson (1989)

May 25, 1997

500mb Closed Lows

From Davies and Guyer (2004)

Typically spawn weak tornadoes, but have been associated with F2 damage.

Can be overlooked because the environments are usually weakly shear with weak thermodynamics.

Tornadoes are often associated with mini–supercells, but can also be non- supercellular because of preexisting vertical vorticity associated with boundaries.

Wind ParametersMicrobursts

Bow Echoes and Derechoes

Microbursts

Atkins and Wakimoto (1991) found “wet” microbursts occurred on days when the delta theta-e between the surface and mid-levels is >20K. Null days occurred when this value is <13K.

Dry microburst tend to occur with high LCLs and steep low level lapse rates.

Bow Echoes and Derechoes

Bow echoes and derechoes are associated with moderate to strong shear in the low levels (Przybylinski, 2001):

<23 kts: Weak Shear (Bow echoes less likely)22-37 kts: Moderate Shear (Bow echoes likely with the greatest threat of damaging winds)>37 kts: Strong Shear (Bow echoes likely with strongest winds remaining above the surface.

Bow Echoes…Typical Morphologies

Bow Echo Squall Line Bow Echo(LEWP)

Cell Bow Echo Bow Echo Complex

Bow Echo

Supercell

Forward Propagating MCS

Forward Propagating MCS

Low Level

Boundary

July 19, 2006 @21Z

For

war

d P

rop.

Vec

tors

1000

-900

mb

CA

PE

850mb T

heta-e1000-900m

b CA

PE

July 21, 2006 @ 13Z

For

war

d P

rop.

Vec

tors

1000

-900

mb

CA

PE

850mb T

heta-e1000-900m

b CA

PE

Back-building and Quasi-Stationary MCSs

‘Classic’ Bow EchoWind Shear Profiles

(Hodographs)

Elevated Hail StormsSteep mid level lapse rates (850 –500 mb lapse rates 7 deg C/km or greater)

MUCAPE > 1000 J/kg

Large CAPE in the -10 to -30oC (-20 to -40oC) range on a sounding

Strong deep shear (through mean cloud layer wind)

Minimized melting effects (lower Freezing levels , WBZ < 10K ft)

Surface Based Storms

1. Mid level updraft rotation (need enough deep shear > 35 kts between 0-6 km AGL)

2. Need steep lapse rates , sufficient low-level moisture, sufficient lifting mechanism (related to CAPE in hail growth zone)

Note: in absence of 1., greater dependence on 2.)

Supercell Hail Forecasting

Large CAPE in the layer that favors rapid hail growth.

0-6-km shear in excess of 30-40 knots supports supercells with persistent updrafts that contribute to large hail production

Lower freezing level heights suggest a greater probability of hail reaching the surface prior to melting

Hail Forecasting Parameters

“Hail Parameters” depicts three forecasting parameters used to predict hail. They are CAPE in the layer from -10 to -30oC, 0-6-km shear vector, and the freezing level height.

The Sig. Hail Parameter (SHIP) was developed using a large database of surface-modified, observed severe hail proximity soundings to determine the potential of hail >2" diameter.

SHIP = [(MUCAPE j/kg) * (Mixing Ratio of MU PARCEL g/kg) * (700-500mb LAPSE RATE c/km)*(-500mb TEMP C) * (0-6km Shear m/s)] / 44,000,000

Both are computed every hour on the SPC Mesoanalysis Page.

Summary

Steps for severe weather forecasting:

Will I have TSRA? (Moisture, Instability, and Forcing)

What will be my primary convective mode and coverage? (Instability, Shear, and Forcing)

What kind of severe weather will I have? (Tornadoes, Hail, Winds)

Convective SeverityDmg winds Hail Tornado FF

Ordinary cell

(0-6km shear <30 kts)

Steep LL lapse ratesHigh LCL, dry midlevels, high DCAPEIntense elevated coreDescending core bottomElevated radial convergence

Cold temps aloftLarge buoyancy ~-20 CIntense elevated core ~ -20 C and colderHigh VIL density, TBSS

No CIN, steep LL lapse ratesSharp boundary with LL vertical vorticityRapidly growing and new CBs

High RH in deep layer; deep warm cloud; small mean wind Slow storm motion Large storm core

Super-cell

(0-6km shear > 30 – 40 kts)

Similar environ as above except for shear and high CAPE & DCAPE, strong 0-1 km shear can assistIn addition to above, LL mesocyclogenesis; developing hook, deep convergence zone

Large buoyancy @-20 C level, strong 0-6 km shear, stg mid- upper SR flow; WER BWER, intense elevated core,mesocyclone,TBSS, high VIL density

Strong 0-1km shear in addition to 0-6 km shear; low LCL; low CINLL TVS, meso, inflow notch; sign of a hook, strong LL convergence below mesocyclone; BWER

High RH in deep layer; deep warm cloud; small SR anvil flowLow supercell motionNot an LP storm

Multicell

(organized group of ordinary/

supercells)

>40kt 0-6km shearStrong >30kt 700-500 wind;Stg leading Gradient;Bookend vortex pair;MARC, deep convergence zone, rear inflow notch

Separated cores; cells exposed to favorable environment

Similar to supercells? Mostly left of rear inflow notches along leading edge of core, front inflow notch with WER and vert vorticity

Slow MBE motion; triple pt anchoring; upwind instability, LL jet, high PW, high mean RHIntrastorm seedingEcho training, slow motion

From DLOC “Hazards

Assessment”

ReferencesAtkins, N.T. and R.M. Wakimoto, 1991: Wet Microburst Activity over the Southeastern US: Implications for Forecasting. Wea. Forecasting, 6, 470-482.

COMET Forecaster’s Multimedia Library, 1996: Anticipating convective storm structure and evolution.

Banacos, P.C., 2003: Severe Weather Threat Assessment. Presentation at the, WDTB Severe Weather/Flash Flood Workshop Course 03-4, Boulder, CO.

Bluestein, H.B. and M.L. Weisman, 2000: The interaction of numerically simulated supercells initiated along lines. Mon. Wea. Rev., 128, 3128-3149.

Brooks, H. E., and J. P. Craven, 2002: A database of proximity soundings for significant severe thunderstorms, 1957-1993. Preprints, 21st Conference on Severe Local Storms, San Antonio, Texas, American Meteorological Society, 639-642.

ReferencesBunkers, M. J., et al. 2006: An Observational Examination of Long-Lived upercells. Part I: Characteristics, Evolution and Demise. Wea. Forecasting, 21, 673-688.

Bunkers, M. J., et al. 2006: An Observational Examination of Long-Lived upercells. Part II: Environmental Conditions and Forecasting. Wea. Forecasting, 21, 689-714.

Burgess, D.W., 2003: Supercells. Presentation at the COMAP Course, Boulder, CO.

Burgess, D.W. and L.R. Lemon, 1991: Characteristics of Mesocyclones Detected During a NEXRAD Test. Preprints, 25th Int. Conf. On Radar Meteorology, Paris, France, AMS, 39-42.

Craven, J. P., 2000: A Preliminary Look at Deep Layer Shear and Middle Level Lapse Rates Associated with Major Tornado Outbreaks. Preprints, 20th Conference on SLS, Orlando, FL, AMS, 547-550

ReferencesDavies, J. L., 2004: Tornadoes in a Deceptively Small CAPE Setting: The "Surprise" 4/20/04 Outbreak in Illinois and Indianahttp://members.cox.net/jondavies3/042004ilin/042004ilin.htm

Davies, J. L., 2002: A Primer on Low-level Buoyancy Parameters When Assessing Supercell Tornado Environments. http://home.kscable.com/davies1/LLbuoyprimer/LLbuoyprimer.htm

Davies, J. M., 2006: Total CAPE, Low-level CAPE, and LFC in significant tornado events with relatively high LCL heights. Preprints, 23rd Conference on SLS, St. Louis, MO, AMS, 59, #P1.3.

Davies, J. M., and J. L. Guyer, 2004: A preliminary climatology of tornado events with closed cold core 500-mb lows in the central and eastern United States. Preprints, 22d Conf. on SLS, Hyannis, MA, AMS, #7B.4.

ReferencesDial, G.L. and J.P. Racy, 2004: Forecasting Short Term Convective Mode and Evolution For Severe Storms Initiated Along Synoptic Boundaries. Preprints, 22nd Conference on SLS, Hyannis, MA, Amer. Meteor. Soc..

Evans, J. and C. Doswell, 2003: Presentation given to WFO Tulsa Staff.http://www.spc.noaa.gov/staff/evans/talk4/talk4_frame.htm

Edwards, R., 2000: Personal Communication.

Edwards, R. and R. L Thompson, 2000: RUC-2 Supercell Proximity Soundings, Part II: An Independent Assessment of Supercell Forecast Parameters. Preprints, 20th Conference on SLS, Orlando, FL, AMS, 236-239.

James, R. P., M. Fritsch and P. Markowski, 2005: Environmental Distinctions between Cellular and Slabular Convective Lines. Mon. Wea. Rev., 133, 2669-2689.

ReferencesKlimoski, Brian A. and R. W. Przybylinski, 2003: Observations of, and Forecasting the Formation and Early Evolution of Bow Echoes. Presentation at the COMAP Course, Boulder, CO.

Lanicci, J. and T. Warner, 1991: A synoptic climatology of the elevated mixed- layer inversion of the southern plains. Part I: Structure, dynamics, and seasonal evolution. Wea. Forecasting, 6, 181-197.

Markowski, P. M., C. Hannon, J. Frame, E. Lancaster, A. Pietrycha, R. Edwards, and R Thompson, 2002: Characteristics of RUC Vertical Wind Profiles Near Supercells. Preprints, 21st Conference on SLS, San Antonio, TX, AMS, 599-602.

Markowski, P. M., E. N. Rasmussen, and J. M. Straka, 1998a: The occurrence of tornadoes in supercells interacting with boundaries during VORTEX-95. Wea. Forecasting, 13, 852-859.

ReferencesMarkowski, Paul M., E. N. Rasmussen, J. M. Straka, D. C. Dowell, 1998b: Observations of Low-Level Baroclinity Generated by Anvil Shadows. Monthly Weather Review: Vol. 126, No. 11, pp. 2942–2958.

Markowski, P. M., E. N. Rasmussen, and J. M. Straka, 2000: Surface Thermodynamic Characteristics of RFDs as Measured by a Mobile Mesonet. Preprints, 20th Conference on SLS, Orlando, FL, AMS, 251-254.

Przybylinski, R.W., 2001: Personal Communication.

Rasmussen, E. N., and D. O. Blanchard, 1998: A Baseline Climatology of Sounding-Derived Supercell and Tornado Forecast Parameters. Wea. Forecasting, 13, 1148-1164.

Rasmussen, E.N., S. Richardson, J.M. Straka, P. M. Markowski, and D. O. Blanchard, 2000: The association of significant tornadoes with a baroclinic boundary on 2 June 1995. Mon. Wea. Rev., 128, 174-191.

ReferencesRasmussen, E.N, and J. M. Straka, 1998: Variations in supercell morphology. Part I: Observations of the role of upper-level storm relative flow. Mon. Wea. Rev., 126, 2406-2421.

SPC Mesoanalysis Page: http://www.spc.noaa.gov/exper/mesoanalysis/help/

Thompson, R. L., 1998: Eta model storm-relative winds associated with tornadic and nontornadic supercells. Wea. Forecasting, 13, 125-137.

Thompson, R.L., 2000: Personal Communication.

Thompson, R.L., R. Edwards, J.A. Hart, K. L. Elmore, and P.M. Markowski, 2003: Close proximity soundings within supercell environments obtained from the Rapid Update Cycle. Wea. Forecasting, 18, 1243-1261.

Thompson, R. L., 2004. Presentation: Forecasting Thunderstorm Coverage and Configuration

ReferencesThompson, R.L., C.M. Mead, and R. Edwards, 2007: Effective Storm Relative and Bulk Shear in Supercell Thunderstorm Environments. Wea. Forecasting, 22, 102-115.

Thompson, R. L., R. Edwards, J. A. Hart, K. L. Elmore, and P. Markowski, 2003: Close proximity soundings within supercell environments obtained from the Rapid Update Cycle. Wea. Forecasting, 18, 1234-1261.

Thompson, R. L. and C. M. Mead, 2006: Tornado failure modes in the central and southern Great Plains. Preprints, 23rd Conference on SLS, St. Louis, MO, AMS, 59, #3.2.

Trapp, R. J., G. J. Stumpf, and K. L. Manross, 2005: A Reassessment of the Percentage of Tornadic Mesocyclones. Wea. Forecasting, 20, 680-687.Wakimoto, R.M., and J.W. Wilson, 1989: Non-Supercell Tornadoes. Mon. Weather Rev., 117, 1113-1140.

Weisman, M. L., and J. B. Klemp, 1982: The Dependence of Numerically Simulated Convective Storms on Vertical Wind Shear and Buoyancy. Mon. Wea. Rev., 110, 504-520.

Documents

Forecasting Convective Mode and Severity