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1

Radar Echoes should be consistent with

-The synoptic situation
-expected or forecast conditions
-knowledge of meteorological theory

2

2 scales used in weather radar

-Precipitation (rate of fall)
-Echo top (top of detectable precipitation

3

Precipitation rate (CAPPI) scale on a radar display

-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)

4

Echo tops scale on radar display

-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

5

Features and indicators of stratiform echo systems

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

6

Features and indicators of cumuliform echo systems

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

7

4 categories of radar indicators for severe weather

-Echo configuration
-Echo Height
-Echo intensity
-Echo Movement

8

Echo configuration

-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

9

LEWP

-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

10

Intersecting Lines

-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)

11

Echoes ahead of a line

-Isolated echos ahead of a line could indicate a gust front or squall line
-indicator of severe Wx

12

Echoes at the trailing edge of a line

-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

13

V-Notches

-V is on opposite side from antenna
-Indicates severe precipitation attenuation, Hail

14

Protuberances or appendages

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

15

Severity of weather is indicated by regional echo tops
what are examples of severe Wx tops in NA

-23000 in Alberta
-47000 in Ontario
-58000 in Texas

16

Taller Echoes
Rapid Growth
Tropopause Penetration

-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

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

-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

Echo movement

-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

Other echoes

-Anomalous propagation
-Fringing
-Precipitation attenuation
-Earth curvature distortion
-Migratory birds

20

Anomalous Propagation

-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

Fringing

-areas of weaker precip may not be detected
-solid echoes are rare with stratiform cloud, but precip can be infered

22

Earth's curvature distortion

-causes echoes to end when the precipitation is still occurring
-composite imagery compensates

23

Angel echoes, Migratory birds

-smaller moving lines
-ground stations and satellite show no precip

24

Radar terminology

-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

Radar coverage values

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

26

Describing convective precipitation

-Describe type with maximum intensity

27

precipitation scale

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

28

Describing Stratiform precipitation

-Describe Maximum coverage

29

Describing Echo tops

-Convective tops - Always give highest tops
- Stratiform tops - Always give average tops
-In 1000s of feet

30

Motion and development time units

-Convection - use increments of 15 minutes
-Stratiform - use increments of up to an hour