doppler 1 presentation message … theme 1 the forecast cycle analysis diagnosis prognosis...
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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)
Comes in … Goes out
Comes in … Goes out
Doppler 22
Doppler Wind Signatures
Constant DirectionBut Speed MaximumHorizontal Flow
Constant DirectionBut Ascending Speed Maximum
Comes in … Goes out
Comes in …Goes out
Doppler 23
Doppler Wind Signatures
Diffluence
Confluence
Continuity requires ascent from below
Continuity requires descent to below
Doppler 24
Doppler Wind Signatures
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
Warm frontal surface
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.
Within the CCB:•Probable Ekman spiral nearest surface•Probable cold advection above Ekman spiral
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.
Increasing CCB Moistening
WCB oriented for
maximum frontal lift
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
Warm frontal surface
Mixing layer
Cold CB
Warm CB
Within the WCB:•West of radar backing, cold advection•East of radar nil VWS
Within the CCB:•Probable Ekman spiral nearest surface•Probable cold advection above Ekman spiral
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.
Increasing CCB Moistening
WCB oriented for
maximum frontal lift
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…
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