Forecasting Convective Mode and Severity Mark F Britt
Forecasting Convective Mode and Severity Mark F. Britt National Weather Service St. Louis, MO Mark. Britt@noaa. gov
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 Numbers There 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 RUC 40 analysis (Thompson et al. (2003) found RUC analysis is a reasonable proxy to observed soundings in supercell environments, except it can be too cool and dry at the lowest levels. ) 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 -800 mb moisture convergence at nose of nocturnal low level jet, orographic lift over the eastern Ozarks)
Moisture Return Lanicci and Warner (1991) 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. Be cognizant of how much dry air is over the Gulf (deep cold front penetrations of cold fronts, buoy data, and Blended Total Precipitable Water: http: //amsu. cira. colostate. edu/GPSTPW/default. htm
Assessing Instability Which is best? SBCAPE MLCAPE MUCAPE
Courtesy Peter Banacos, SPC (2003) 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.
Courtesy 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.
Courtesy Peter Banacos, SPC (2003) MUCAPE: Most Unstable Parcel. Uses most unstable parcel in lower atmosphere (SPC uses lowest 300 mb). Helps with nocturnal or other types of elevated convection.
What Do I Do With This? ? RUC MUCAPE -March 12, 2006 @ 17 Z
What Do I Do With This? NAM MUCAPE - March 12, 2006 @ 17 Z
Surface Based Parcels Violent tornado outbreak over western Missouri. KSGF RAOB May 5 th, 2003 @ 00 Z
Elevated Based Parcels Numerous Reports of Hail in Eastern NE/ Western IA KOAX RAOB May 4 th, 2003 @ 18 Z
CAPE vs. Parcel Selection April 20, 2004 Mean Layer CAPE Surface Based CAPE From Jon Davies Webpage
How Tall is the CAPE? April 20 th, 2004 @ 22 Z From Jon Davies Webpage (http: //members. cox. net/jdavies 1/)
How Tall is the CAPE? April 20 th, 2004 From Jon Davies Webpage
How Wide Is the CAPE? COMET 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. 7 o 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 -3 km AGL) can give a better idea on how quickly convection will develop.
Mid Level Lapse Rates 500 mb Heights/500 -700 mb Lapse Rates -- May 2003 Friday, May 9 th @ 12 Z
Mid Level Lapse Rates 500 mb Height/500 -700 mb Lapse Rates – March 11 -12, 2006 Sat Morn – 12 Z Sat Eve – 00 Z Sun Morn – 12 Z Sun Eve – 00 Z
Inhibiting Factors Boustead (2007) theorized that subsidence from a shortwave ridge caused a “null” “High Risk” day in the central Plains in June 1999. 12, 18, & 00 Z @ OAX – 06/5 -6/1999
Assess Vertical Shear Distribution of vertical shear will determine dominant thunderstorm type. Can be determined using either: Traditional fixed layers (0 -6 km bulk shear, 0 -1 km 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 and CIN >-250 J/kg. (Thompson 2007)). Effective shear on mesoanaylsis data is dependent on correct RUC soudings. Low level curvature can determine if right-movers, leftmovers, or both kinds of splits are favored.
Storm Type: Ordinary Cells Dominant Type in Weak Shear Environments Pulse Type Severe Storms. COMET
Storm Type: Multicells COMET Moderate to strong shear is confined mainly to the lower levels (0 to 3 km AGL)
Organized Multicells >40 kt 0 -6 km shear >30 kt 700 -500 mb wind Dry (low theta-e) midlevel air (strong cold pool) Downshear SBCAPE max System relative convergence acting downshear to enhance forward propagation
Storm Type: Supercells Thompson et al. (2003) found that 90% of the 2” diameter hail reports were caused by supercells. Recent work showed that from only 25% (Trapp et al. 2005) to as few a 3% (Jones et al 2004) of radar-detected mesocyclones were actually associated with tornadoes.
Deep Shear Magnitude 0 -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. (Thompson et al. , 2004 b) While 0 -6 km shear is a good discriminator between cell types, it isn’t a good tornado forecast tool (Thompson et al, 2002). Houston et al. (2008) found in a study that compared 250 nonsupercell soundings to 829 supercell soundings that the best fixed layer shear depth to discriminate between the two is 0 -5 km.
Deep Shear Magnitude Bunkers et al. 2006 found that in a study of 440 supercells that: Long-lived supercells (those lasting >4 hrs) occur in environments with much stronger 0 -8 km bulk wind shear ( > 50 kt) than that observed with short-lived supercells. Long lived supercells produce notably more F 2–F 5 tornadoes when compared with short-lived supercells, and a single long-lived supercell can also produce a substantial amount of nontornadic severe weather.
0 -6 km Shear Magnitude Supercells Non. Supercells From Thompson et al (2002)
Supercell Composite Parameter (SCP) (Thompson et al, 2004 a) The SCP is a multi-parameter index that includes effective SRH, mu. CAPE, and effect Bulk Shear. Each parameter is normalized to supercell “threshold” values. It is conditional on having discrete storms develop. SCP = (mu. CAPE / 1000 J kg-1) * (ESRH / 50 m 2 s-2) * (EBWD / 20 m s-1) EBWD is divided by 20 m s-1 in the range of 10 -20 m s-1. EBWD less than 10 m s-1 is set to zero, and EBWD greater than 20 m s-1 is set to one. (Computed every hour on the SPC Mesoanalysis Page. )
Supercell Composite Parameter (SCP) (March 8, 2009 -16 Z)
What Causes Supercell Type Rasmussen and Straka (1998) found in an observational study of 43 isolated supercells that supercell type depends on the precipitation efficiency of the storm which is 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 Dimensions Falcon Co Hurr. Opal “mini” “large” Horizontal Dimension Pond Bank PA Burgess (2003) “mini” Vertical Dimension Cone of Silence “low-topped” “high-topped” “low-topped”
Supercell Movement Bunkers et al (2000) A physically based, shear-relative, and Galilean invariant method based on 290 supercell hodographs.
Supercell Movement Bunkers 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)
What’s the Problem? Evans and Doswell (2002) noted Strong Forcing Derechoes and discrete, significant tornadic supercells (F 2 -F 5) can occur in similar environments. Different types of supercells can be found in the same environment. 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. Thompson et al. (2008) found in a study of 359 significant tornado cases that included 864 individual significant tornadoes that the largest tornado outbreaks (events with >6 F 2 -F 5 tornadoes) were dominated by discrete cells, whereas Quasi-Linear Convective Systems produced 33% of singular events. 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 rates Combination 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 smallscale/shallow processes for initiation) Large CIN (Confine storms to “strongly forced” or in areas of most persistent ascent) 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.
Supercells or Squall Line? Discrete Linear weaker Strength and Depth of Forcing stronger 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 *surface boundaries w/ horizontal temperature gradient of 2. 5 -5 o. C/100 km or 300 mb jet max of 50 -70 kts
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 -60 o: (discrete supercells, little storm interaction) 90 o: (colliding storm splits, but depends on storm spacing and hodograph shape)
Progressive Trough May 4 th 2003 Tornado Outbreak, Progressive Flow Aloft 0 -6 km shear across dryline, and storm motion faster than boundary motion From Rich Thompson, SPC
Progressive Trough March 12 th 2006 Tornado Outbreak, Progressive Flow Aloft 0 -6 km shear across boundary, and storm motion faster than boundary motion
High Amplitude Trough April 6 th 2001 Great Plains “High Risk” Squall Line 0 -6 km shear largely parallel to dryline, and storm motion slower than boundary motion From Rich Thompson, SPC
(March 11 -13, 2006) Deep Shear vs. Boundary Orientation Sat Eve – 04 Z Sun Aftn – 21 Z Sun Eve – 00 Z Sun Eve – 06 Z
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 Parameters Supercell Tornadoes Low Level Shear Vector and Storm Relative Helicity Low Level Thermodynamic Profile 1. Height of LCL 2. Low Level CAPE and CIN Boundaries Non-Supercell Tornadoes
0 -1 km Shear Vector Brooks and Craven (2002) Supercells associated with significant tornadoes Non-Tornadic 20 kts 15 kts 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 -1 km helicity (Thompson et al, 2002). Does not require knowledge of storm motion.
0 -1 km Shear Vector F 4 March 8 th, 2009 – 03 Z EF 2 March 13 th, 2006 – 03 Z EF 2
0 -1 km Storm Relative Helicity Thompson et al (2002) Supercells associated with significant tornadoes Non- Tornadic
0 -1 km Storm Relative Helicity SRH can vary up to two orders of magnitude within 100 km and 3 hrs. No good threshold, but 100 m 2/s 2 is considered a good lower number with increasing threat as the numbers grow. Outbreaks 200 -300 m 2/s 2. (Rasmussen and Blanchard, 1998 and Thompson et al, 2002). Esterheld and Giuliano (2008) found in an examination of 65 supercell events that even a smaller depth (10 m – 0. 5 km) is a better discriminator of storm classes (i. e. Non Tor. vs. Weak Tor. vs. Sig. Tor) than 10 m – 1000 m. Thompson (2007) found effective SRH discriminated sig-tor better than non-tor cases.
0 -1 km Storm Relative Helicity May 4 th, 2003 @ 22 Z April 20 th, 2004 @ 23 Z From Banacos (2003) From Jon Davies Webpage
0 -1 km Storm Relative Helicity F 4 March 8 th, 2009 @ 16 Z EF 2 March 13 th, 2006 @ 03 Z EF 2
Wind Shear Conway, MO Profiler
(March 12 -13, 2006) Sunday Evening Base Reflectivity – 0040 Z Base Reflectivity - 0313 Z Base Reflectivity - 0142 Z Base Reflectivity – 0443 Z
Hodograph Kinks Four 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 5/04/2003 -20 Z SGF 3/13/2006 -03 Z
Height of the LCL (Mean Layer) COMET Markowski (2000) speculates that lower LCL heights (< 1000 m) mean high boundary layer RH and increased buoyancy in the RFD. Davies (2006) studied 44 “high” (1, 300 -2, 000 m) LCL cases, but they had the othermodynamic and kinematic factors (including sizeable total and 0 -3 km CAPE) that are very favorable for supercells. Height of the LCL should be considered a limiting factor instead of an necessary ingredient.
Height of the MLLCL From Thompson et al (2002) From Brooks and Craven (2002)
Let’s Take a Look ILX 5/11/2003 @ 00 Z Classic supercells which produced several strong tornadoes.
Boundaries serve two important functions: Local forcing mechanisms for convective initiation. As a source of vorticity augmentation in mesocyclones. Boundaries may be difficult to identify.
How Important Are Boundaries? Yes!!!: Significant tornadoes usually require higher quantities of SRH than is normally provided. They often require augmentation from boundaries. (Markowski et al (1998 a)) Maybe? : However, Thompson et al. (2008) found that only 35 -40% of their tornado cases (F 2 -F 5) involved a potential storm and surface interaction compared to 70% (F 1 -F 4) during VORTEX-95. In their study of 359 events, boundary interactions were found in a larger percentage of isolated significant tornado cases (46%) vs. during events when there were six or more significant tornadoes (33%)*. Garner (2007) found in a study of 36 events that more long path tornadoes (>25 miles) occurred in environments with no detectable synoptic-scale surface boundary (i. e. fronts) compared to those with shorter paths. * Percentage is likely lower because multiple tornadoes occurring in close proximity were counted as one case.
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 m 2 s– 2 or 0 -10 km shear of ~100 kts per Markowski et al (1998 b).
Outflow From External Thunderstorms Rasmussen (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.
Boundaries Markowski et. al. (1998 b) 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, 2002 Courtesy Fred Glass
Anvil Boundaries Preferred direction for longer parcel residence times. 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.
Significant Tornado Parameter (Thompson et al, 2004 a) The Significant Tornado Parameter is a multi-parameter index. that includes 0 -6 km shear magnitude, 0 -1 km storm-relative helicity, surface based CAPE, and surface based parcel LCL height. STP = (sb. CAPE/1500 J kg-1) * ((2000 sb. LCL)/1500 m) * (SRH 1/100 m 2 s-2) * (6 BWD/20 m s-1) * ((200+sb. CIN)/150 J kg-1) 1. When the sb. LCL is less than 1000 m AGL, the sb. LCL term is set to one. 2. When the sb. CIN is greater than -50 J kg-1, the sb. CIN term is set to one. 3. The 6 BWD term is capped at a value of 1. 5, and set to zero when 6 BWD is less than 12. 5 m s-1. Computed every hour on the SPC Mesoanalysis Page.
Significant Tornado Parameter (Thompson et al, 2004 a) EF 2 March 8 th, 2009
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 Kis et al. (2008) found in numerical modeling experiments that tornadogenesis can occur independently of the midlevel mesocyclone. Low level rotation can occur because of angular momentum transported to near the ground by hydrometers.
Non-Supercell Tornadoes May 25, 1997 From Wakimoto and Wilson (1989)
500 mb Closed Lows Typically spawn weak tornadoes, but have been associated with F 2 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. From Davies and Guyer (2004)
Wind Parameters Microbursts 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 >20 K. Null days occurred when this value is <13 K. 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). 0 -3 km bulk shear magnitude determines their potential and attendant severe weather production: <23 kts: Weak Shear (Bow echoes less likely) 22 -37 kts: Moderate Shear (Bow echoes likely with the greatest threat for damaging winds/greatest probability for non-supercell tornadoes to occur) >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) Supercell Cell Bow Echo Complex Bow Echo
Forward Propagating MCS
1000 -900 mb MLCIN 1000 -900 mb MLCAPE Forward Prop. Vectors 850 mb Theta-e July 19, 2006 @21 Z
1000 -900 mb MLCIN 1000 -900 mb MLCAPE Forward Prop. Vectors 850 mb Theta-e July 21, 2006 @ 13 Z
Back-building and Quasi. Stationary MCSs
Elevated Hail Storms Steep mid level lapse rates (850 – 500 mb lapse rates 7 deg C/km or greater) above the inversion. MUCAPE > 1000 J/kg Large CAPE in the -10 to -30 o. C (-20 to -40 o. C) range on a sounding Strong deep shear (through mean cloud layer wind) Minimized melting effects (lower Freezing levels , WBZ < 10 K 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 -30 o. C, 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 -500 mb LAPSE RATE c/km)*(-500 mb TEMP C) * (0 -6 km Shear m/s)] / 44, 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 Severity Dmg winds Ordinary cell (0 -6 km shear <30 kts) Supercell (0 -6 km shear > 30 – 40 kts) Multicell (organized group of ordinary/ supercells) Hail Tornado From DLOC “Hazards Assessment” FF Steep LL lapse rates High LCL, dry midlevels, high DCAPE Intense elevated core Descending core bottom Elevated radial convergence Cold temps aloft Large buoyancy ~ -20 C Intense elevated core ~ -20 C and colder High VIL density, TBSS No CIN, steep LL lapse rates Sharp boundary with LL vertical vorticity Rapidly growing and new CBs High RH in deep layer; deep warm cloud; small mean wind Slow storm motion Large storm core Similar environ as above except for shear and high CAPE & DCAPE, strong 0 -1 km shear can assist In 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 -1 km shear in addition to 0 -6 km shear; low LCL; low CIN LL 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 flow Low supercell motion Not an LP storm >40 kt 0 -6 km shear Strong >30 kt 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 RH Intrastorm seeding Echo training, slow motion
References Atkins, 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. Boustead, J. M. and P. N. Schumacher, 2007: Identification of Inhibiting Factors of a Null Significant Tornado Event. NWA Electronic Journal of Operational Meteorology, 2007 -EJ 5 Brooks, H. E. , and J. P. Craven, 2002: A database of proximity soundings for significant severe thunderstorms, 1957 -1993. Preprints, 21 st Conference on Severe Local Storms, San Antonio, Texas, American Meteorological Society, 639642.
References Bunkers, 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, 25 th 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, 20 th Conference on SLS, Orlando, FL, AMS, 547 -550 Davies, J. L. , 2004: Tornadoes in a Deceptively Small CAPE Setting: The "Surprise" 4/20/04 Outbreak in Illinois and Indiana http: //members. cox. net/jondavies 3/042004 ilin. htm
References Davies, J. L. , 2002: A Primer on Low-level Buoyancy Parameters When Assessing Supercell Tornado Environments. http: //home. kscable. com/davies 1/LLbuoyprimer. htm Davies, J. M. , 2006: Total CAPE, Low-level CAPE, and LFC in significant tornado events with relatively high LCL heights. Preprints, 23 rd Conference on SLS, St. Louis, MO, AMS, 59, #P 1. 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, 22 d Conf. on SLS, Hyannis, MA, AMS, #7 B. 4. Dial, G. L. and J. P. Racy, 2004: Forecasting Short Term Convective Mode and Evolution For Severe Storms Initiated Along Synoptic Boundaries. Preprints, 22 nd Conference on SLS, Hyannis, MA, Amer. Meteor. Soc. 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, 20 th Conference on SLS, Orlando, FL, AMS, 236 -239.
References Esterheld, J. M. and D. J. Giuliano, 2008: Discriminating between tornadic and nontornadic supercells: A new hodograph technique. Electronic J. Severe Storms Meteor. , 3 (2), 1 -50. Evans, J. S. , and C. A. Doswell III, 2002: Investigating Derecho and Supercell Proximity Soundings. Preprints, 21 st Conf. Severe Local Storms, San Antonio. Garner, J. : A Preliminary Study on Environmental Parameters Related to Tornado Path Length. NWA Electronic Journal of Operational Meteorology, 2007 -EJ 5. Houston, A. L. , R. Thompson and R. Edwards, 2008: The Optimal Bulk Wind Differential Depth and the Utility of Upper-Tropospheric Storm-Relative Flow for Forecasting Supercells. Wea. Forecasting. , 23, 825 -837. James, R. P. , M. Fritsch and P. Markowski, 2005: Environmental Distinctions between Cellular and Slabular Convective Lines. Mon. Wea. Rev. , 133, 2669 -2689.
References Jones, T. A. , K. M. Mc. Grath, and J. T. Snow, 2004: Association between NSSL Mesocyclone Detection Algorithm-detected vortices and tornadoes. Wea. Forecasting, 19, 872 -890. Klimoski, 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, 21 st Conference on SLS, San Antonio, TX, AMS, 599 -602. Markowski, P. M. , E. N. Rasmussen, and J. M. Straka, 1998 a: The occurrence of tornadoes in supercells interacting with boundaries during VORTEX-95. Wea. Forecasting, 13, 852 -859.
References Kis, K. K. , J. M. Straka, and K. M. Kanak, 2008; Nocturnal Tornadoes and Low-Level Static Stability. 24 th Conference on SLS, Savannah, GA. Markowski, Paul M. , E. N. Rasmussen, J. M. Straka, D. C. Dowell, 1998 b: Observations of Low-Level Baroclinity Generated by Anvil Shadows. Mon. Wea. Rev. : 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, 20 th 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, 11481164. 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.
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