Doppler 1 Presentation Message … Theme 1 The Forecast Cycle Analysis Diagnosis Prognosis...

Doppler 1

Presentation Message … Theme 1

The Forecast Cycle

• Analysis

• Diagnosis

• Prognosis

• Verifinosis

Human Skills ……….

Pattern Recognition

Anticipation versus reaction

Conceptual Models

You are the most important part of the Forecast Cycle

Take the Forecast Cycle for a Spin

Doppler 2

Presentation Message … Theme 2

Remote Sensing is your Friend

Fantastic Time & Space ResolutionAnimation

For Real Time A&D

The actual atmosphere is the best tool and teacher…

For Lead Time

Today’s Topic

Doppler 9

Doppler Patterns - Outline• Doppler Basics• Doppler Signatures

– Basic Signatures• Wind Analysis (Meso and

Synoptic Flows)

– Advanced Signatures• Atmospheric Diagnosis (VWS,

Stability, Trends in both)

• Conveyor Belt Conceptual Model (CBCM)

• Summary

Many of the following signatures will only be evident in Doppler –

Clouds obscures the low level, precipitating signatures in Satellite

Imagery.

Doppler 10

Doppler Patterns

Analysis and Diagnosis for All SeasonsThe Doppler Mantra

‘Look for Something “Odd”’“Look UP ”

Doppler 12

Doppler Radar Quantities – The Data• Backscattered power (R)

– equivalent reflectivity factor and

– estimates of the precipitation rate

• Mean radial velocity (V)• Spectral width of radial velocity of

targets within the sample volume (W)

Integral of S(v) over V

R=

Mean Radial V

Spectral Width

Doppler 13

Spectral Width and “Doppler Display Texture”

Rain DopplerTexture

Snow DopplerTexture

Doppler 14

Velocity Azimuth Display - VAD• At a given height (h), then the radial velocity is: Vr• For a uniform flow field, assume Vw (Vertical Velocity) approximately = 0• Best fit of a sine curve to the observations around the circle.

Maximum Inbound

Maximum Inbound

Maximum Outbound

Maximum Outbound

No Radial

Doppler 18

Doppler Radar Analysis and Diagnosis Quantities• Determining the

Horizontal Winds– Curvature

– Confluence

– Wind Shear

– VWS Trends

– Thermal Advections

– Trends in time/space

• Stability– Stability Trends

• Doppler Texture and Spectral Width– Precip Phase

Know the limitations of the data…

Doppler 19

Horizontal Wind Determination

Max/Min Method

Comes in … Goes out

Caution:•Not all flows are uniform•Important flows not uniform

Doppler 20

Horizontal Wind Determination

Zero Isodop Method

Caution:•Think the pattern through•Deduces important non-

uniform flows

The Purple VectorsHave ZERO radialComponent – Not measured.

Com

es in

… G

oes

out

Method:•Draw Radial from radar•Wind perpendicular to radial•Pointing toward warm

Isodop Method reveals details!

Doppler 21

Doppler Wind Signatures

Constant Directionand Speed

Constant DirectionBut Speed IncreasesWith Height (Range)



Doppler 22


Constant DirectionBut Speed MaximumHorizontal Flow

Constant DirectionBut Ascending Speed Maximum


Comes in …Goes out

Doppler 23


Diffluence

Confluence

Continuity requires ascent from below

Continuity requires descent to below

Doppler 24


BackingCounter-clockwiseIsodop

VeeringClockwiseIsodop

Cold Advection

Warm Advection

With Height

With Height

Wind normal to Isodop andIsodop relative to its starting orientation

Doppler 25

Doppler Wind Signatures - Doppler Vortex

‘Look for Something “Odd”’

Broad

Sca

le F

low

Doppler 26

‘Look for Something “Odd”’

Doppler Radial diffluence

Doppler Radial confluence…

Doppler Wind Signatures - Doppler Downburst

Higher…

Doppler 27

Doppler Wind Shear

Zero Isodop Method

Bac

kB

ack

Winds Back with height = VWS = Cold advection

Isodop Arc backs or is counter-clockwise with height/rangeCold VWSCold Advection(relative to radar)

Doppler 28

Doppler Wind Shear•“look for something odd”

Winds Veer with height = VWS = Warm advection

Vee

rV

eer

Isodop Arc veers or is clockwise with height/range Warm VWSWarm Advection(relative to radar)Think in 3-D

Doppler 29

Vertical Discontinuities“look for something odd”

SW -

Leve

l

SE - Level

SW -

Leve

l

follow a range ring for vertical discontinuities

Doppler 30

Horizontal Discontinuities “look for something odd” follow a radial looking for discontinuities that

do NOT follow along a range ring…

SW -

Leve

l

?

NW – Level ?

Doppler 32

The Doppler Texture is smooth. What is it?

1. Hail

2. Freezing Rain

3. Rain

4. Snow

Doppler 34

The Doppler shows an area of zero velocity. What does it mean?

1. There is no wind.

2. The wind is parallel to the radar beam.

3. The wind is perpendicular to the radar beam.

4. There is no precipitation.

Per

pend

icul

ar

Doppler 39

Doppler Patterns

Analysis and Diagnosis for All SeasonsThe Doppler Mantra

‘Look for Something “Odd”’“Look UP ”

Doppler 42

Doppler Practice

Low Level Veering

What are the implications for vertical stability?

“look for something odd”W

arm

ing

Co

oli

ng

Black range ring separates Veering Isodop from Backing Isodop

Under High Level Backing

Doppler 44

Doppler Wind Analysis – More Practice

Isodop Wind Analysis

• Follow isodop outward

• Draw line from radar

• Wind is perpendicular to this radial, towards the red echoes

Doppler 45

Doppler Wind Analysis – More Practice

For any height you can determine the wind in four locations• Determine the two isodop winds• For the maximum winds look roughly 90° away from the isodop winds•The wind maxs are where the winds align along a radial•Full wind toward radar •Full wind away from radarAnalyze areas of non-uniform flow• curvature from direction• confluence from speed

At 5.3 km … Anticyclonic Ridge with mass confluenceSubsidence below. Nil pcpn above.What’s your short range forecast?

Doppler 46

Doppler Wind Analysis – Even More Practice

Below Discontinuity •NLY winds veering 30o with height•Warm advection •Max wind rising a lot•ACYC curvature•No sig confluence ….23kts in 23kts out….

Synoptic Situation … Zonal frontal zone with stable wavesWarm front slanted toward the NNW. Subsidence below.but strong Cold Conveyor Belt – nil motion

Discontinuity Slope •2.4 km SE rising to 2.8km NW•2.7 km S steady to 2.7 N

Above Discontinuity •SLY winds nil directional shear•Nil thermal advections •ACYC curvature•Mass confluence …60kts in only 45kts out..

23

23

Range Ring Discontinuity - Difference in the Vertical

Isodop Discontinuity•Veers clockwise•Warm front

Doppler 48

The location of the max inbound and max outbound reveals flow:

1. Curvature

2. Convergence/divergence

3. Ascent/descent

4. All of the above

5. None of the above

Doppler 49

AB

C

D

•Determine wind at B. Draw radial from radar site A to the isodop at B.

•Determine wind at C.

•Wind backs from B to C. Relative to A the isodop backs or turns counter-clockwise.

•Determine wind at D.

•Wind veers from C to D. Relative to A the isodop veers or turns clockwise.

Summary

VWS Diagnosis VWS

Isodop Method= VWS Inflection

Thermal Advection Intensity•The larger the angle subtended by the arc, the larger the wind shift and stronger the thermal advections.•This wind shift/angle independent of range from radar Thermal Advection Type – Relative to Radar Site•If isodop turns counter-clockwise with height (increasing range), arc associated with cold advection… winds back with height.•If isodop turns clockwise with height (increasing range), arc associated with warm advection… winds veer with height.•The VWS inflection at the limiting radial marks the range/height separating backing and veering portions of the isodop.

Doppler 51

Thermal Advections and VWS

AB

C

AB

C

AB

C

•Angle subtended by the counter-clockwise isodop BC is identical in 1, 2 and 3.•In 1, winds back over a short radial range•Radial range & height difference increases for 2•Radial range difference is even more for 3•Height interval for the Thermal VWS increases with the length of the radial DC from case 1 to 3•Thermal VWS determined by dividing the directional shear (isodop angle) by the height interval (Difference between AC and AD=DC):

•Strongest for 1•Moderate for 2•Weakest for 3.

•Thermal VWS is proportional to the size of the subtended angle divided by the radial range (AC-AD=DC) which is inversely proportional to area BCD

1.

2.

3.

D

D

D

VWS = WS

Depth

Isodop Angle

Radial Height Change =

1

Isodop Area (BCD) ~

~1/Small Area~1/Medium Area~1/Large Area

Isodop

Range Ring

Radial

Doppler 55

Doppler Isodops for Increasing ?

AB

C1.

D

Stronger cold advection BCLevel C

Weaker cold advection CDStabilization

Level D

Level B

A

B C

2. D

Weaker warm advection BCLevel C

Stronger warm advection CDStabilization

Level D

Level B

AB

C

3. D

(Weak) Cold advection BCLevel C

(Strong) Warm advection CDStabilization

Level D

Level B

Note: Angles kept constant.Changing the Thermal Advection Intensity by changing the depth of the directional wind shear.

Backing Wind Turning Along the Radial

Veering Wind Turning Along the Rings

Stability

Doppler 56

Isodop Diagnosis of Stabilization Trends

Stability increases with:• Cold advection decreasing with height:

– Angle of backing Doppler isodop veers to become more aligned along a radial,

• Warm advection increasing with height:– Angle of veering Doppler isodop veers to

become more aligned along the range rings,

• Cold advection under warm advection:– Doppler isodop backing counterclockwise with

height (range) under Doppler isodop veering clockwise with height (range).

• Following the Isodop – for Stabilization

AB

C

A

B C

D

AB

C

D

Cold Advection - Backing Veers

Warm Advection - Veering Veers

Important Generalization: For Stabilization isodop veers with height/range

Remember:Veering with Height =Warming with Height =Stabilization (Red = Stop)

Doppler 63

An operational guide to getting the most information from Doppler radar:• Look for Something “Odd”• Determining the actual Wind Direction and Speed – Blue towards Red Away

Curvature from direction & Mass confluence from speed• Determining VWS - Wind backing & veering with height

for Thermal AdvectionsAngle subtended by Isodop veers for Warm AdvectionAngle subtended by Isodop backs for Cold Advection

• Determine Trends in the VWS - Angle between the Isodop and Range RingsIf angle (area) increases (in time) then vertical wind shear/thermal advection is decreasingIf angle (area) decreases (in time) then vertical wind shear/thermal advection is increasing

• Determining Stability Trends -Isodop backing & veering with height relative to range ringsFor Stabilization Isodop veers with height/rangeFor Destabilization Isodop backs with height/range

Stabilization/Destabilization rate stronger for longer legs… • Diagnosing Vertical versus Spatial wind discrepancies

Along a Range Ring versus along Radial

… some of this is probably new to you … I made it up :>)

StrongerDestabilization

Doppler Analysis & Diagnosis Strategies

IncreasingDecreasing

StrongerDestabilization

Discontinuities in theVertical

Follow the range rings

Discontinuities in theHorizontal

Tend to be lines Not along range rings

Doppler 76

Doppler and the Conveyor Belt Conceptual Model

North of the Surface Warm Front Conceptual Models

RCL

R = Right of the ColC = Centered on the ColL = Left of the Col

End

Doppler 77

The Conveyor Belt Conceptual Model

End

SL

Y F

low

s R

isin

g Is

entr

op

ical

ly

NL

Y F

low

s S

inkin

g Isen

trop

ically

Think in 3-D

Vee

rin

g

Bac

kin

g

Div

Doppler 78

Vertical Deformation Zone Distribution & CBMSimplified Summary

C

C

WC

B

DCB

CCB

DCB

C

WCB overrides the warm frontCCB undercuts the warm front

Frontal surface overlies mixing layer

Looking along the WCB flow:•In WCB right of the Col expect veering winds with height – Katabatic (red for stop) warm front•In WCB approach to the Col expect maximum diffluence – the eagle pattern with ascent and increasing pcpn•In WCB to the left of the Col expect backing winds with height – Anabatic (green for Go) warm front

Vee

rin

g

Nil

VW

S

Bac

kin

gCCB wind shear variable

End

Doppler 79

CCB Doppler Diagnosis – Conceptual Models

A

B

C

The Beaked Eagle

•A is the radar site•AB is backing with height indicative of cold advection where really there should be veering as a result of the Ekman Spiral•BC is veering with height indicative of warm advection•B is the front with the mixing layer hidden in the cold advection•This is a strong cold advection•The warm front will be slow moving or stationary

A

B

C

The Headless Eagle

•A is the radar site•ABC is all veering with height indicative of warm advection. Layer AB is apt to be partially the result of the Ekman Spiral•BC is veering with height indicative of warm advection•Where is the front and the mixing layer?•The cold advection is not apparent and the warm front will advance

The CCB Conceptual Model is independent of that in the

WCB. Like Mr. Potato Head, one can mix and match

conceptual models in the distinctly different conveyor

belts.

End

The best Beaked Eagle always has strong cold advection in the PBL.

The Headless Eagle has nil cold advection in the PBL.

-Be Alert for ZR -ZR not a serious threat

Doppler 80

WCB to the Right of the Col

o

C

Warm frontal surface

Mixing layer

Cold CB

Warm CB

Within the WCB:•East of radar veering, warm advection•West of radar nil VWS

Within the CCB:•Probable Ekman spiral nearest surface•Probable cold advection above Ekman spiral

The Warm Right Wing Stoop CM

The eagles right wing is folded in as if it is about to swoop down.The left wing is still fully extended to catch the lift of the WCB.

Right W

ingLe

ft W

ing

Signature ofWarm Frontal surfaceWarm

advection

End

Doppler 81

WCB

CCB

Warm Frontal Cross-section along Leading Branch of the Warm Conveyor

Belt (WCB)

Cold air in Cold Conveyor Belt (CCB) deep and dry

Moist portion of Warm Conveyor Belt (WCB) is high and veered from frontal perpendicular – katabatic tendency

Dry lower levels of WCB originate from ahead of the system and veered from frontal perpendicular

Mixing Zone

SurfaceWarm Front

Frontal slope is more shallow than the typical 1:200

Precipitation extends equidistant into the unmodified CCB

Precipitation extends further into the moistened, modified CCB

Increasing CCB Moistening

WCB oriented for

maximum frontal lift

WCB oriented for

less frontal lift

Virga Precipitation

Lower

Hydrometeor

Density

Common location for virga and the virga hole A

B

A B

WCB typically veers with height (it is after all, a warm front)

End

Inactive or Katabatic Warm Front

Winds veer with height above the warm front to the right of the COL

Winds in warm airAbove front

slower Than front

Descen

t into

DIV

EndVeering winds mean stable Knot active Red for “Stop”

Frontal Speed

Speed abovefront

Doppler 83

o

C


Mixing layer

Cold CB

Warm CB

Within the WCB:•East of radar veering, warm advection – katabatic warm front.•West of radar backing, cold advection – anabatic warm front.


The Warm Screaming Eagle CM

Both wings are fully extended to catch the lift of the WCB. This is a divergent signature.

Right W

ingLe

ft W

ing

Signature ofWarm Frontal surface

discontinuity

End

WCB Approaching the Col

Doppler 84

WCB

CCB

Warm Frontal Cross-section along Central Branch of the Warm Conveyor

Belt (WCB)

Cold air in Cold Conveyor Belt (CCB) more shallow and moist

Moist portion of Warm Conveyor Belt (WCB) is thicker, higher and perpendicular to front

Lower levels of WCB have the same origin as the upper level of the WCB - frontal perpendicular

Mixing Zone

SurfaceWarm Front

Frontal slope is near the typical 1:200Precipitation extends further into the moistened, modified CCB.


WCB oriented for


Virga Precipitation

Lower

Hydrometeor

Density

Common location for both precipitation and virga A

B

A B

WCB shows little directional shift with height. A greater WCB depth is frontal perpendicular

PrecipitationAt Surface

End

Horizontal rain area begins to expand as CCB moistens.

Doppler 85

BCAD

E

F

G

H

Need to emphasizeThe PPI nature of theDoppler scan- The cone

The Warm Screaming Eagle Conceptual Model End

A Beaked Warm Screaming Eagle has CAA in the PBL

Doppler 86

C


Mixing layer

Cold CB

Warm CB

Within the WCB:•West of radar backing, cold advection•East of radar nil VWS


o

The Warm Left Wing Stoop CM

The eagles left wing is folded in as if it is about to swoop down.The right wing is still fully extended to catch the lift of the WCB.

Right Wing

Le

ft W

ing

Signature ofWarm Frontal surfaceWarm

advection

Signature ofWarm Frontal surface… odd?

End

WCB to the Left of the Col

Doppler 87

WCB

CCB

Warm Frontal Cross-section along Trailing Branch of the Warm Conveyor

Belt (WCB)

Cold air in Cold Conveyor Belt (CCB) even more shallow and more moist

Moist portion of WCB is thicker, higher and backed from frontal perpendicular – anabatic tendency

Lower levels of WCB have the same origin as the upper level of the WCB

Mixing Zone

SurfaceWarm Front

Frontal slope likely steeper than the typical 1:200

Precipitation extends further into the moistened, modified CCB.


WCB oriented for


Virga Precipitation

Lower

Hydrometeor

Density

Common location for precipitation to ground! A

B

A B

WCB backs slightly with height in spite of the warm air advection. A greater WCB depth is frontal perpendicular

PrecipitationAt Surface

End

Horizontal rain area expands rapidly as CCB moistened.

Doppler 88

ABC

D

F

G

End

A

B

Doppler 89

Active or Anabatic Warm Front

Winds back with height above the warm front to the left of the COL

Winds in warm airAbove front

faster Than front

con

flu

enc

e U

P

EndBacking winds mean unstable Active Green for “Go”

Frontal Speed

Speed abovefront

Doppler 90

Veering winds above a frontal surface denotes the front as:

1. Anabatic2. Katabatic3. Warm Frontal4. Cold Frontal5. Advancing 6. Stationary 1 2 3 4 5 6

17% 17% 17%17%17%17%

10

Doppler 91

Backing winds above a frontal surface denotes the front as:

1. Anabatic

2. Katabatic

3. Warm Frontal

4. Cold Frontal

5. Advancing

6. Stationary 1 2 3 4 5 6

17% 17% 17%17%17%17%

10

Doppler 93

Given the Doppler Radar image, where is the radar relative to the conveyor belt conceptual model?

1 2 3 4

25% 25%25%25%

1. Downstream from the Col

2. Under the Col

3. Upstream from the Col

4. In the warm sector

10

Doppler 94

Given the Doppler Radar image, where is the radar relative to the conveyor belt conceptual model?

1 2 3 4

25% 25%25%25%

1. Downstream from the Col

2. Under the Col

3. Upstream from the Col

4. In the warm sector

10

Doppler 95

The Doppler Radar of the cold conveyor preceding a warm front shows the “Beaked Eagle”. What can be said about this

front?

A

B

C

The Beaked EagleRadar

1. Strong cold advection from A to B

2. B is the lower level of the frontal mixing zone

3. BC is the warm frontal mixing zone

4. Cold advection overpowers the typical frictional Ekman Spiral

5. Warm front nearly stationary

6. Beware of freezing precipitation

7. All of the above

8. None of the above.

Doppler 96

Doppler Patterns - Outline• Doppler Basics• Doppler Signatures

– Basic Signatures• Wind Analysis (Convection,

Synoptic Flows)

– Advanced Signatures• Atmospheric Diagnosis

(VWS, Stability)

• Conveyor Belt Conceptual Model (CBCM)

• Summary

Keep Looking UP!

Take Home Message (THM):Doppler Radar is useful to A&D winds, VWS, Stability & Stability Trends!

Thank you for your attention!Remote sensing is your Friend!

Doppler 97

And Now You Know What This Means…The Headless Screaming Eagle Conceptual Model

No Cold Advection in PBL

Where is the Conveyor Belt?

Where is Frontal Surface?

ZR-?

These patterns happen every day – somewhere…

Doppler 1 Presentation Message … Theme 1 The Forecast Cycle Analysis Diagnosis Prognosis...

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