310 Flashcards
500hPa chart parameters
-18000ft, 5500m.
-contours are at 6 decameter intervals.
522, 546,570,594 contours are accentuated
-Height centers are black L or H as appropriate
-Two charts, 500hPa vorticity (early)
500hPa thickness (complete)tx
500hPa Vorticity
- twice daily, based on 00z and 12z data
- tx 2 hours after obs
- 500 hPa contours and isopleths
- signs are maximum absolute vorticity
- signs are minimum absolute vorticity
- dashed lines are isopleths of absolute vorticity at regular intervals labelled 0,4,8…
500 hPa Thickness
- twice daily, based on 00z and 12z data
- tx 3.5 hours after obs
- dashed lines are 1000-500 hPa thickness isopleths analyzed at 6 decameter intervals, labelled in decameters
- indicates high thickness,- indicates low thickness, labelled in decameters
500 hPa vorticity enhancements
-Vorticity centers- Max -red C or plus sign
Min - blue A or minus sign
Shortwave trough- red line
ridge - blue line
Vorticity advection
area - PVA- red shading
- NVA - blue shading
Advection
- the transport of an atmospheric property solely by the mass motion of the atmosphere
- the smaller the quadrilateral the stronger the advection
- when isopleths are parallel to the contour lines there is no advection.
PVA
Positive Vorticity Advection
- found in advance of disturbances aloft (shortwave)
- enhances the potential for thunderstorms.
- excellent indicator of where instability may develop
NVA
Negative Vorticity Advection
-Movement of negative vorticity towards an area of higher vorticity
-convergence at upper levels
-
500 hPa thickness enhancements
-Height centers - black H or L
-Thickness centres- Warm - red W
Cold - blue C
trough -dashed blue lines
ridge - dashed red line
- Thickness advection -PthA red shading
-NthA blue shading
-540 dm contour - dashed yellow
PthA
Positive Thickness Advection
- A thicker layer moves over a point
- supports cyclogenesis
- fronts usually located in the ridges (warm tongue)of the thickness field
- area between 534 and 540 dm indicate chnge of phase zone.
Prog SFC-400 mb
- low and mid level weather
- pressure centers, surface frontal positions
- surface position of tropical storms
- significant cloud
- turbulence, freezing level, icing
- prepared twice daily, valid 00z and 12z, issued 11 hours before validity
Comox Prog
- forecasst issued for a period of 12,24,36 hours
- west coast and pacific
- ground to upper levels
CMC Sig Wx Prog
- 700mb - 400mb
- composite of forecasts from across canada
- produced 4 times daily, issued 1 hour after GFA.
- essentially a GFA, but for mid level flight
- Surface pressure centers, fronts, tropical storms
- sig cloud, turb, icing , freezing level
Upper winds forecast
-winds and temps for FL240,340, 450
Mid-level prog chart features
- H and L are in colour, as it is a prog chart
- standard met markings for fronts etc
- showery precipitation - green outline, hatched
- Cont or INTMT shown as solid green, stipled
- clouds are scalloped brown
- icing is solid blue outline, stipled
- turb is solid red, hatched
- freezing level-freezing levels, 5000ft intervals, labled in 100s of feet.
Interpolation
- the estimation of values between known values
- accuracy dependent on density of grid points
- topography and local effect must be taken into consideration
