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Flashcards in Review of weather charts Deck (59)
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1

Isobars are

the solid lines (they are NOT height contours)

2

Unlike the upper air charts, this chart is

not at a constant pressure level

3

Frictional force is significant on this chart. Turns wind about

30 degrees toward low pressure. This causes convergence into low pressure regions.

4

Strong fronts will cause

"kinking" of isobars

5

WHAT TO LOOK FOR:

  1. Fronts: cold fronts, warm fronts, troughs, outflow boundaries, occluded fronts, stationary fronts, drylines
  2. Pressure: High pressure regions, low pressure regions
  3. Convergence, divergence
  4. Temperature and moisture gradients
  5. Influence of topography upon the weather conditions

6

............................. will cause the low levels of the atmosphere to become increasingly unstable

  • Warm air advection and moisture advection near the surface
  • The temperature must be increasing rapidly and the dewpoint increasing rapidly

 

 

7

. If the morning temperature and dewpoint are 60/47 and the afternoon temperature and dewpoint are 87/70,

a large amount of warm air advection (WAA) and moisture advection have taken place throughout the day

8

The temperature must be increasing rapidly and the dewpoint increasing rapidly for the atmosphere to rapidly become unstable. If the morning temperature and dewpoint are 60/47 and the afternoon temperature and dewpoint are 87/70, a large amount of warm air advection (WAA) and moisture advection have taken place throughout the day. If a trigger mechanism is nearby

strong storms are very likely

9

The temperature must be increasing rapidly and the dewpoint increasing rapidly for the atmosphere to rapidly become unstable. If the morning temperature and dewpoint are 60/47 and the afternoon temperature and dewpoint are 87/70, a large amount of warm air advection (WAA) and moisture advection have taken place throughout the day. If a trigger mechanism is nearby, strong storms are very likely. If a mT airmass extends from

the surface to the upper levels of the atmosphere, severe weather is not as likely

10

The temperature must be increasing rapidly and the dewpoint increasing rapidly for the atmosphere to rapidly become unstable. If the morning temperature and dewpoint are 60/47 and the afternoon temperature and dewpoint are 87/70, a large amount of warm air advection (WAA) and moisture advection have taken place throughout the day. If a trigger mechanism is nearby, strong storms are very likely. If a mT airmass extends from the surface to the upper levels of the atmosphere, severe weather is not as likely. Look for

differential advection for severe weather (mT air in low levels with cT or cP air in midlevels of atmosphere.)

11

  1. The 850 mb vhart

What do I need to look for on this chart?

 

  • Chart is good for assessing low level warm air and cold air advection
  • Region of strong thermal gradient gives indication of 850 millibar front and regions of convergence
  • Use dew-point depression to determine if atmosphere is near saturation or dry at this level
  • Determine intensity of highs and lows

12

Advection is a function of

height contour spacing, the temperature gradient, and the angle isotherms cross height contours

13

Low level warm air advection contributes to 

to synoptic scale rising air

14

; Low level cold air advection contributes to

synoptic scale sinking air

15

Air rises due to

low level convergence and confluence

16

Deep high (surrounded by several height contours) covering a

large spatial area

17

Determine intensity of highs and lows

  1. Deep low (surrounded by several height contours)
  2. Deep high (surrounded by several height contours) covering a large spatial area
  3. Disregard highs and lows not surrounded by at least one isohypse
  4. Several highs located near each other indicates one broad area of high pressure and not a scattering of individual highs

18

Thermal advection is a function of three factors:

(1) the temperature gradient,

(2) the height contour spacing and

(3) the angle the isotherms make with the height contours.

19

Thermal advection is maximized by the combination of:

  1. Closely spaced isotherms
  2. Closely spaced height contours
  3. Isotherms perpendicular to height contours

20

Thermal advection is minimized by the combination of:

1. Widely spaced isotherms

2. Widely spaced height contours

3. Isotherms parallel to height contours

21

  1. The 700 mb Chart

look for

The trough/ridge pattern becomes more defined at the 700 mb levels as compared to lower levels

22

if trough and ridge appear in 700 mb it will be

deep on 500 mb

23

2.     The 500 mb chart

warm advection in 500 mb means that there is 

upward motion

24

areas bellow the trough are

cooled

25

A

CAA

26

B

WAA

27

Therefore, in general warmer than average temperatures can be expected

underneath ridges

28

colder than average temperatures can be expected

underneath troughs

29

The more pronounced the ridge (or trough), the

more above (or below) average the temperatures will be.

30

The terminology "trough" and "ridge" is related to the fact that

the contour lines often look like waves