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Mod3 > 309 > Flashcards

309 Flashcards

1
Q

Radar Echoes should be consistent with

A
  • The synoptic situation
  • expected or forecast conditions
  • knowledge of meteorological theory
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2
Q

2 scales used in weather radar

A
  • Precipitation (rate of fall)

- Echo top (top of detectable precipitation

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3
Q

Precipitation rate (CAPPI) scale on a radar display

A
  • Radar site and type
  • setting (rain or snow) (snow is 1/5 as reflective as water equivelant of rain
  • rate of fall in mm/hr
  • # of pixels in nm (0.5nm/pixel)
  • ring scale (25 nm per ring)
  • Time of image (utc)
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4
Q

Echo tops scale on radar display

A
  • Radar site and type
  • Altitude (elevation in feet)
  • Echo top in kms and 100s of feet
  • # of pixels in nm (0.5nm/pixel)
  • Ring Scale (25 nm per ring)
  • Time of image
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5
Q

Features and indicators of stratiform echo systems

A

Feature Indicator

  • Gradient -From weak to moderate
  • Persistence -variable, fm hours to days
  • Growth -Slow
  • Tops -Low and uniform
  • Intensity Levels -Low
  • Signatures -none
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6
Q

Features and indicators of cumuliform echo systems

A

Feature Indicator

  • Gradient -Moderate to very strong
  • Persistence -Variable
  • Growth -Can be very rapid
  • Tops -Very high, can penetrate tropopause
  • Intensity levels -High
  • Signatures -Cellular, can be very distinct
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7
Q

4 categories of radar indicators for severe weather

A
  • Echo configuration
  • Echo Height
  • Echo intensity
  • Echo Movement
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8
Q

Echo configuration

A
  • Line Echo Wave Pattern LEWP
  • Intersecting lines
  • echoes ahead of a line
  • Echoes at the trailing edge of a line
  • V-notches
  • Protuberances or appendages
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9
Q

LEWP

A
  • Damaging winds, Hail and tornadoes
  • Discontinuity of speed along a line of echoes
  • 2 Meso high caused by TS
  • Local wind fields cause low level convergence at the apex of the LEWP
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10
Q

Intersecting Lines

A
  • Occurs where a local effect and a main synoptic feature cross or collide eg. Cold front intersecting with a convergence line (sea breeze)
  • Severe Wx at intersecting point (tornadoes)
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11
Q

Echoes ahead of a line

A
  • Isolated echos ahead of a line could indicate a gust front or squall line
  • indicator of severe Wx
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12
Q

Echoes at the trailing edge of a line

A
  • The last cell in a solid or broken line often is associated with the most severe weather
  • Ensure you are looking at the end of the line
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13
Q

V-Notches

A
  • V is on opposite side from antenna

- Indicates severe precipitation attenuation, Hail

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14
Q

Protuberances or appendages

A
  • Indication of attenuation of tornado hook
  • Rear right quadrant relative to storm motion
  • Very high reflectivity and echo tops
  • Very strong gradient
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15
Q

Severity of weather is indicated by regional echo tops

what are examples of severe Wx tops in NA

A
  • 23000 in Alberta
  • 47000 in Ontario
  • 58000 in Texas
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16
Q

Taller Echoes
Rapid Growth
Tropopause Penetration

A
  • Echoes taller than their neighbors are more likely to produce severe weather
  • Rapid growth can indicate severe weather
  • Tropopause Penetration can indicate severe weather
17
Q

Echo intensity
Strong intensity gradients
High intensity in trailing quadrants
High intensity at long range

A
  • echoes indicating a rate of fall greater than 50mm/hr imply possibility of severe weather
  • Strong gradients can indicate hail
  • More reliable indicator than protuberances
  • indicates severe storms
18
Q

Echo movement

A
  • Colliding Cells -tornadoes can form at the merge point
  • Echo speed-relatively high speed >60km/h =SVR Wx
  • Motion to the right of mean flow-deviation of >30’ of mean flow
  • Persistence
19
Q

Other echoes

A
  • Anomalous propagation
  • Fringing
  • Precipitation attenuation
  • Earth curvature distortion
  • Migratory birds
20
Q

Anomalous Propagation

A
  • Super-refraction associated with a strong nocturnal inversion -Ground stations, satellite will show clear
    - Echoes are stationary,dissipate with daytime heating
  • Sub-refraction-Shows clear when ground stations and satellite report cloud
21
Q

Fringing

A
  • areas of weaker precip may not be detected

- solid echoes are rare with stratiform cloud, but precip can be infered

22
Q

Earth’s curvature distortion

A
  • causes echoes to end when the precipitation is still occurring
  • composite imagery compensates
23
Q

Angel echoes, Migratory birds

A
  • smaller moving lines

- ground stations and satellite show no precip

24
Q

Radar terminology

A
  • Type- Convective or stratiform cloud
  • Area coverage- Related to size and geography
  • Cell- single cell
  • Cells- up to three individual cells
  • Area- related or similar echoes grouped geographicall
  • Line- length of 5-1 and at least 60km at least 30% coverage
25
Q

Radar coverage values

A 
<1/10- widely scattered
1/10-5/10 - scattered
6/10 - 9/10 - Broken
10/10 - Solid
-cell is always solid
26
Q

Describing convective precipitation

A

-Describe type with maximum intensity

27
Q

precipitation scale

A 
VRY STG - very strong
STG - strong
MDT-STG - moderate to strong
WK - MDT - Weak to Moderate
VRY WK - Very Weak
28
Q

Describing Stratiform precipitation

A

-Describe Maximum coverage

29
Q

Describing Echo tops

A
  • Convective tops - Always give highest tops
  • Stratiform tops - Always give average tops
  • In 1000s of feet
30
Q

Motion and development time units

A
  • Convection - use increments of 15 minutes

- Stratiform - use increments of up to an hour

31
Q

Remarks

Terminology to avoid

A
  • use for non-standard features or for clarification

- Quantitive rates,technical terms

32
Q

Canadian Lightning Detection Network

A
  • Overlayed over radar display
  • good for confirming convective activity
  • Depicted as a small red circle
  • Data collected every minute, sent to MSC and Nav Canada
  • accurate to 500 m
33
Q

Azimuth

Noise

Propagation

A
  • A horizontal straight line path represented by a number of degrees rotation from true north
  • Any unwanted, usually random fluctuation in signal or emission from a non radar source
  • The passage of microwave energy through a medium
34
Q

Refraction

A

Process whereby the direction of energy propagation within a medium is changed as a result of varying density of the medium.

Mod3 (9 decks)

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