s5 03edwards extended version for end of day

Dabby

Download

Post to :

URL :

Related Presentations :

Add to Flag Embed

Uploaded from authorPOINTLite

Views: 48

Category: News & Reports..

Presentation Description

No description available.

Comments

Presentation Transcript

Slide1:

The State of Tropical Cyclone Tornado Prediction

Slide3:

HISTORY of TC TORNADO UNDERSTANDING Showalter 1943 (USWB tornado report) Dissipating stages of inland TC Dunn 1944 (AAF Weather Wing report) Several TC tornadoes documented No quadrant favored Tannehill 1950 (“Hurricanes” update) Forward (north) semicircle, advancing periphery Sadowski 1962 (MWR, Carla Tornadoes) First TC tornado known: 14 Aug 1773

Slide4:

TC Able: Franconia VA Tornado of 1 Sep 1952 Malkin and Galway 1953 Proximity RAOB: Wet, low lapse rate unlike Fawbush-Miller “loaded gun” Time of day not related (SOS) Examined horizontal shear (anticyclonic) HISTORY of TC TORNADO UNDERSTANDING

Slide5:

TC Carla Tornadoes of Sep 1961 Sadowski 1962 TC-relative right semicircle Outer tornadoes part of “short pre-hurricane squall line” (SOS) All tornadoes in < gale wind area HISTORY of TC TORNADO UNDERSTANDING

Slide6:

HISTORY of TC TORNADO UNDERSTANDING Hill et al. 1966 (JAM climatology of 136) Most likely with stronger “cells” in outer rainbands, NE quad >80% of Carolinas/VA TC tornadoes from FL landfalls Report vs. occurrence dilemma (“generally haphazard reporting” practices) Dry intrusions aloft and convective instability association

Slide7:

TC Beulah 19-23 Sep 1967 Orton 1970 Then-record 115, 67 on one day (20th) Almost all reports in azimuthal NE quad All but 2 reports outside hurricane force wind area HISTORY of TC TORNADO UNDERSTANDING

Slide8:

HISTORY of TC TORNADO UNDERSTANDING Novlan & Gray 1974 (MWR climatology for 373) Up to 10% of deaths, 0.5% of damage in TCs Tornadoes during post landfall dissipation phase (partly SOS) Favored time 1100 (SOS) Prefer cartesian NE quad vs. Lagrangian RF quad

Slide9:

HISTORY of TC TORNADO UNDERSTANDING Novlan & Gray 1974 (MWR climatology for 373) Tornadic (vs non): increase in shear vector thru 0-5 kft Vertical shear from stabilizing overland parcels (SOS) Large, westward-skewed hodographs

Slide10:

HISTORY of TC TORNADO UNDERSTANDING Gentry 1983 (MWR, updated climatology) Nearly every hurricane between BRO-NYC 60% of TS’s (22 year climatology) Short land-trajectory air mass favored for friction Enhances vertical shear through sfc drag Increases convection through convergence (lift) Favored sector N-ESE of center ~20% in inner bands to just outside eyewall Favored time 1200-1800 LST

Slide11:

TC Danny Tornado Outbreak of Aug 1985 Long-track (up to 150 km, 3h) tornadic supercells First TC-tornado photos: multiple vortices, wall cloud Giant 0-1 and 0-3 km hodo HISTORY of TC TORNADO UNDERSTANDING REDSTONE ARSENAL TORNADO Photos by A. Junkins McCaul 1987

Slide12:

HISTORY of TC TORNADO UNDERSTANDING Weiss 1987 (Hurr. Conf. preprint, climo aspects of TC tornado forecasting, 1964-83 data) TIME: 2/3 during daylight, afternoon spike of >F2 50% between -3 to +12 h of landfall 51% with center < 60 nm from coast Mainly NE quad, none firmly in SW quad Post-landfall tornadoes mainly in east semicircle

Slide13:

HISTORY of TC TORNADO UNDERSTANDING McCaul 1991 (MWR, environmental composites for 1948-1996 U.S. tornadic TCs) Low level shear stronger than Oklahoma supercell composite Enhanced vertical shears and SRH in RF quadrant Shear differences between quads related to “superimposed across-hurricane shear in steering current.”

Slide14:

HISTORY of TC TORNADO UNDERSTANDING McCaul 1991 (MWR, environmental composites for 1948-1996 U.S. tornadic TCs) ~ Moist adiabatic thermal profiles, CAPE increasing outward Strong diurnal signal, late morning to early afternoon sun time Diurnal peak not sampled by 12/00 Z RAOB data used

Slide15:

HISTORY of TC TORNADO UNDERSTANDING McCaul & Weisman 1996 (MWR, TC supercell numerical simulation) Shear, buoyancy maximize together in low levels Dynamic VPGFs yield >3x updraft speed of CAPE alone Weak cold pools restrict sfc vorticity, maybe limit tornado strength vs. Plains supercells

Slide16:

HISTORY of TC TORNADO UNDERSTANDING Spratt et al. 1997 (WAF, WSR-88D examination) Gordon-94, Allison-96 – mini-supercells Discrete >50dBZ with cell-relative Vr 13-30 kt Core SRM couplet diameter contracted to ~1 nm at touchdowns Rotation/storm depth ratios similar to Plains supercells Proximity VWP useful for LL shear diagnosis

Slide17:

HISTORY of TC TORNADO UNDERSTANDING Edwards 1998 (Hurr. Conf.) Distinct landfall and exit phase tornado clusters Exit phase tornadoes with return to sea, following Gulf or FL landfall Beware post-landfall production drop Baroclinic influences apparent for every exit-tornado event

Slide18:

HISTORY of TC TORNADO UNDERSTANDING SLU/SPC/MLB collaborations, 1999-2004 RADAR Cross-sections resemble compressed Great Plains storms Bow echoes with tornadoes and/or damaging cell-scale winds Threat enhanced with supercells crossing baroclinic boundaries into strongly sheared, still buoyant air (Earl-98) Threat suppressed with supercells crossing baroclinic boundaries over cold/stable boundary layers (Floyd-99) MM5: Vertical component of 925 mb vorticity for mesocyclones

Slide19:

HISTORY of TC TORNADO UNDERSTANDING Curtis 2003 (WAF, TCs with >20 tornadoes) Midlevel drying atop 11/13 such outbreaks Only 3 drying cases 1960-2002 didn’t yield outbreaks Sharp midlevel RH gradients juxtaposed with favorable low level shears of NE quadrant

Slide20:

TC TORNADO PREDICTION TODAY Ready… Get Set… GO! WARNING: WFO Hide now! WATCH: SPC+WFO Be ready to take reinforced shelter if tornado warning issued or tornado seen OUTLOOK: SPC Tornadoes possible with approaching TC -- Make sure shelter is available EVENT

Slide21:

TC TORNADO PREDICTION TODAY Day-3 Outlooks CATEGORICAL PROBABILISTIC Example: TC Charley (2004)

Slide22:

TC TORNADO PREDICTION TODAY Day-2 Outlooks CATEGORICAL PROBABILISTIC Example: TC Charley (2004)

Slide23:

TC TORNADO PREDICTION TODAY Day-1 Outlooks CATEGORICAL PROBABILISTIC Example: TC Charley (2004) TORNADO

Slide24:

TC TORNADO PREDICTION TODAY Mesoscale Discussions

Slide25:

TC TORNADO PREDICTION TODAY Watches

Slide26:

TC TORNADO PREDICTION TODAY Climatology/Pattern Recognition NE quad, sometimes NW or SE, mainly gale area, sometimes inner bands More profuse with big hurricanes but common with TSs (i.e., Beryl-94, Frances-98, Bonnie-04) Recognized (i.e. NE quad, mainly gale wind area) but taking backseat to… Physical understanding Low LCL…low downdraft cooling Ambient vs. in-storm kinematic geometry Boundary interactions with bands/supercells Drying aloft: influences on lapse rates and heating

Slide27:

TC TORNADO PREDICTION TODAY Operational models Resolve meso-b and smaller scale processes very poorly in TC setting May be useful in blended parameters May indicate most probable area of passage of climatologically favored TC sector (outlook time frame) Some promise in research models (i.e. MM5)

Slide28:

TC TORNADO PREDICTION TODAY Radar characteristics for warnings BASE REF: Persistent discrete cells, especially if right-moving vs. others Anomalously high dBZ, especially if sudden or persistent Hook, appendage, bow or kidney bean (indicates wrapping meso) SRM: Strong/persistent mesocyclone or couplet at lowest cut “Spike” in horizontal shear values coincident with tornadogenesis SPECTRUM WIDTH: Tight cluster of high “turbulence” juxtaposed with horizontal shear CROSS SECTIONS: Vertically compressed vault, BWER, tilt Weak or unproductive couplet or persistent cell approaching favorable boundary (use mesoanalysis!) Range limitation critical for shallow mini-supercells Vertical sampling and overshooting lowest 1-3 km AGL Horizontal beam/gate width problems occur at closer range

Slide29:

TC TORNADO PREDICTION TODAY Mesoanalysis for supercell/tornado potential Assessment of boundaries Buoyancy – largest CAPE on one side? Shear (SRH & Bulk shear)– often maxed along and to one side Convergence – maximized along Intersections (i.e., front + spiral band) Morphology of pre-existing boundaries (fronts) Formation of in-situ boundaries (i.e., diff. heating) Pressure fall maxima Hand analysis very critical SPC objective analyses show promise despite RUC kinematic flaws near TC cores

Slide30:

TC TORNADO PREDICTION TODAY Radar Characteristics

Slide31:

TC TORNADO PREDICTION TODAY Radar Characteristics

Slide32:

TC TORNADO PREDICTION TODAY Manual Diagnosis Confining front, buoyancy: Floyd-99

Slide33:

TC TORNADO PREDICTION TODAY Manual Diagnosis Confining front, shear: Earl-98

Slide34:

TC TORNADO PREDICTION TODAY Manual Diagnosis Confining front, CAPE+shear: Charley-04

Slide35:

TC TORNADO PREDICTION TODAY Objective Diagnosis CAPE & Shear, “Confining Front – Both” case Boundary provided LIFT (and maybe BL vorticity)

Slide36:

TC TORNADO PREDICTION TODAY Objective Diagnosis SPC Supercell Composite & Significant Tornado

Slide37:

Supercell Composite Parameter (SCP) SCP includes: MUCAPE BRN shear term 0-3 km SRH Designed to highlight environments favoring right-moving supercells.

Slide38:

SCP Formulation SCP = ( MUCAPE / 1000 J kg-1 ) X ( BRN shear / 40 m2 s-2 ) X ( 0-3 km SRH / 100 m2 s-2 ) RULES: SCP = 1 when MUCAPE = 1000 J kg-1, BRN shear = 40 m2 s-2, and SRH = 100 m2 s-2.

Slide39:

SCP Distribution right-moving supercells mainly non-supercells

Case Example:

Case Example