Analysis of reflectivity echo.ppt

8/22/2019 Analysis of reflectivity echo.ppt

1/136

Analysis of reflectivity echo


2/136

Analysis of reflectivity echo


3/136


4/136


5/136


6/136

Rainfall Estimation Limitations

Brightband

Contamination

Radar Centered Arch of Higher

Rainfall Accumulations on prouduct.

Overestimate

rainfall

But rare to

affect convectiveflash flooding

events


7/136

Rainfall Estimation Limitations

Inaccurate Z/R relationship due to

estimation of drop size distributions

Same Reflectivity,

Vastly Different

Rainrates


8/136

Mixed shape


9/136

Mixed shape


10/136


11/136

Anticipating Dominant Warm Rain

Process Convection

Assess the environment


12/136

Ft. Collins Flood (07/28/97)

12z and 00z Denver U/A soundings


13/136

Efficiencyschematic


14/136

Precipitation in

Flash Floods Enhanced Intensity

Precipitation efficiency

Tropical, maritime

connection Deep, above-freezing

layer

Low-level jet, rapid

moisture replenishment Low-level focus (terrain

and boundary)

http://www.comet.ucar.edu/class/FLOAT_2001/index.htm


15/136

Flash flood threat from weakly

sheared cells

Warm cloud depth

increases collision

coalescenceresulting in

excessive rainfall

rates

Storm top may not

be high

W R i P


16/136

Warm Rain Processes

Radar Signatures

Kansas Turnpike Flash Flood Aug 30, 2003

LEC

C S ti th h W


17/136

Cross Section through Warm-

Rain Supercell


18/136


19/136


20/136


21/136

0.5


22/136

V shape notch


23/136


24/136

Hook shape echo

The hook echo is always located the right

rear of the main echo movement.

The hook echo is always associated with

meso-cyclone and hailstorm.

When the meso-cyclone is detected using

lowest ( 0.5 elevation angle ) , a tornado

may occur.


25/136


26/136


27/136


28/136


29/136


30/136


31/136


32/136


33/136


34/136


35/136


36/136


37/136


38/136


39/136


40/136


41/136


42/136


43/136


44/136


45/136


46/136


47/136


48/136


49/136

200252708:55 gmt)

2.4deg

3.4deg1.5deg

0.5deg


50/136


51/136

Same supercell at max BWER


52/136

Same supercell at max BWER

detection range Large BWER

is barely

visible @ 78

nm or only148 km

-20

C

Wide lower topped supercell


53/136

Wide, lower topped supercell

updraft

Front-flankupdraft

Very wideupdraft

Prolific 5.5 cmhail and 45 m/swinds

-20

C

BWER = 5mi max size


54/136


55/136

The Weak Echo Region

WERs are ellipticalin shape

Is that the shape ofthe updraft?

7.3 km AGL 45

dBZ

reflectivity

contour

10 km

O i i f th W k E h R i


56/136

Origin of the Weak Echo Region

Quarter Panel Display


57/136

Quarter Panel Display6/18/1992

Severe sheared updraft intensity


58/136

Severe sheared updraft intensity BWER detection

BWER (Bounded Weak Echo Region)

0.5

1.5

2.4

3.4

BWERs

difficult

to detect

this far

out

Typical

BWER topnear the

-20to -25o

C level

-20C

Needs a

connection to

the low-level

WER

Classic severe updraft


59/136


signature case

Right-rearupdraft

Typical width

Produced a fewrecord sized

hailstones

BWER = 2mi max size

-20

C



60/136

Classic severe updraftsignature case

Velocity

-20

C


61/136

Example

>45 dBZ echo

to 7300 m AGL

hookWER

BWER


62/136

Radar Characteristic of Severe


63/136

StormsIn a Sheared Environment

Strong low-level reflectivity gradients.

Displaced low-level Echo Core.

Occasionally concaved echo open to inflow. Mid-level sloping echo overhang: WER*.

Strong upper mid-level echo core over low-level reflectivity gradient/concavity.

Echo top above mid-level echo core. * Sometimes BWER

After Lemon, 1980.

Remember these 6 characteristics!!

On updraft flank:

Summary: Severe updraft


64/136

Summary: Severe updraftsignatures

severe updraft signatures common to allstorms in order of most severe first

BWER

WER

Intense and deep reflectivity core relative to the

20C level

Storm top displaced over WER

Deep convergence zone*

Supercell Visual Appearance


65/136

p pp


66/136

The gust front


67/136


68/136


69/136

2013/11/4

2 69

SA


70/136

2013/11/4

2 70


71/136


72/136


73/136


74/136


75/136


76/136


77/136

( f ) ( )


78/136

13: 42 (left ) 13: 51 (right )

Li l i d lti ll t


79/136

Linearly-organized multicell storms

W kl ti ll li


80/136

Weakly convective squall line


81/136

S t i l


82/136

Some terminology

Squall line: multicell convection organizedinto laterally-aligned cells that may or maynot be interacting

Bow echo: a squall line with a bow-shaped morphology

Gust front- leading edge of downdraft-driven convective storm outflow

T i l ( td)


83/136

Terminology (contd)

Mesoscale Convective System(MCS)A multicell convective complex

Most often includes a radar-observed linear

organization in its mature phase May be relatively disorganized

In its largest, longest-lived formsbecomes a Mesoscale ConvectiveComplex (MCC)

A satellite view of an MCS


84/136

A satellite view of an MCC


85/136

MCS schematic cross section


86/136

MCS schematic cross-section

Morphology and Evolution


87/136

Morphology and Evolution

Role of air flows in complex multicell system

3 distinct modes (TS, LS, and PS)

Parker and Johnson (2000)


88/136


89/136


90/136

Bow Echoes


91/136

From Fujita, 1978, the morphology of the typical

Bow Echo.

Echo is bowed towards the direction of the echo movement.

A bow echo is often associated with strong surface winds at the

leading of the bow echo.

Bow Echoes Important 3-D features


92/136

Development of Cyclonic bookend vortex

Affects strength of RIJ

Can be an area of increased downdrafts (non-supercell and

supercell tornadoes)

p

Elevated RIJs

Line-end vortices

RINs Strong reflectivity

gradient

Weak Echo Regions

Displaced echo top

Supercell transition

Bow Echoes


93/136

Bow Echoes

Rear-Inflow Notch (RIN) May indicate a descending RIJ


94/136

Bow Echoes


95/136

Supercell transition to Bows


96/136


97/136

Can you apply the Lemon


98/136

technique here?

Yes, accountingfor storm motion, a

WER and BWER

can be detected

-20

C

WERand

BWER

along

leading

edge


99/136


100/136


101/136


102/136

Summary: Severe updraft


103/136

signatures

severe updraft signatures common to allstorms in order of most severe first

BWER

WER Storm top displaced over WER

Deep convergence zone

Intense reflectivity core, and deep relative to the20C level


104/136


105/136


106/136

Volumetric Radar Data


107/136

AZ/RAN 272o/172 km

3 km (10 kft)

9.1 km (30 kft) 12.2 km (40 kf

6.1 km (20 kft

Volumetric Radar Data


108/136

AZ/RAN 293o/67 km

Ground-Relative Wind ProductionM h i


109/136

Mechanisms

Much more than a simple downburst

HL

+5mb

-2mb

roun - e a ve n ro uc onMechanisms


110/136

Mechanisms

Most likely area for XDW is on outflow flank oflow-level mesocyclone and in the precip-filled


111/136


112/136

The Gust front


113/136


114/136


115/136

(CR 37)


116/136

(CR 37)


117/136

(STI 58)


118/136

(HI 59)


119/136


120/136


121/136

(HSR 33)


122/136

(ET 41)


123/136

(V 27)


124/136

(VWP 48)


125/136

1(OHP 78)


126/136

3(THP 79)


127/136


128/136

(VIL 57)


129/136

(SW 30)


130/136


131/136


132/136


133/136

()


134/136

( )


135/136

2005614


136/136

08:43(gmt) 08:55(gmt) 09:08(gmt)

2002527

Analysis of reflectivity echo.ppt

Documents

Transcript of Analysis of reflectivity echo.ppt