chapter2 part2

Question 1

Cyclogenesis refers to

Answer 1

the initial development and strengthening of surface cyclones in the middle latitudes of the globe

Question 2

Norwegian Cyclone Model

stage 1

Answer 2

The precursor condition for cyclogenesis is the existence of a stationary front (baroclinic zone) separating warm air to the south from cold air to the north.

Question 3

Norwegian Cyclone Model

1) The precursor condition for cyclogenesis is the existence of a stationary front (baroclinic zone) separating warm air to the south from cold air to the north.

stage 2

Answer 3

A wave on the front will form with the approach of an upstream mid-to upper-tropospheric perturbation. The front develops a “kink” creating a cyclonic circulation and a cyclone is born.

Question 4

Norwegian Cyclone Model

1) The precursor condition for cyclogenesis is the existence of a stationary front (baroclinic zone) separating warm air to the south from cold air to the north.
2) A wave on the front will form with the approach of an upstream mid-to upper-tropospheric perturbation. The front develops a “kink” creating a cyclonic circulation and a cyclone is born.

Answer 4

3) As the wave intensifies, both cold and warm fronts become better organized.

Question 5

Norwegian Cyclone Model

1) The precursor condition for cyclogenesis is the existence of a stationary front (baroclinic zone) separating warm air to the south from cold air to the north.
2) A wave on the front will form with the approach of an upstream mid-to upper-tropospheric perturbation. The front develops a “kink” creating a cyclonic circulation and a cyclone is born.
3) As the wave intensifies, both cold and warm fronts become better organized.

Answer 5

4) The wave becomes a mature low pressure system, while the cold front, moving faster, overtakes the warm front, an occluded front forms.

Question 6

Norwegian Cyclone Model

1) The precursor condition for cyclogenesis is the existence of a stationary front (baroclinic zone) separating warm air to the south from cold air to the north.
2) A wave on the front will form with the approach of an upstream mid-to upper-tropospheric perturbation. The front develops a “kink” creating a cyclonic circulation and a cyclone is born.
3) As the wave intensifies, both cold and warm fronts become better organized.
4) The wave becomes a mature low pressure system, while the cold front, moving faster, overtakes the warm front, an occluded front forms.

Answer 6

5) As the cold front continues advancing on the warm front, the occlusion increases and eventually cuts off the supply of warm moist air, causing the low pressure system to gradually dissipate

Question 7

Using satellite imagery, an area of cyclogenesis can be found through a process where the following features are identified:

Answer 7

1. A baroclinic zone (frontal cloud band) - F
2. Upstream perturbations - X
3. An emerging layer cloud - E

Question 8

As seen in the surface cyclone conceptual model, the……………………….. is an important precursor to cyclogenesis.

Answer 8

surface baroclinic zone

Question 9

frontal band

Answer 9

The mid-level manifestation of this surface baroclinic zone is highlighted on the satellite image . This cloud pattern is also called the “frontal band”.

Question 10

Outside of the frontal band, there is little chance of

Answer 10

extratropical cyclogenesis because of the lack of baroclinicity

Question 11

This frontal band is relatively

Answer 11

strong as indicated by a well-defined moisture field of significant breadth

Question 12

Upstream Perturbations
 These are identified as

Answer 12

vorticity maxima (trough axes) poleward side of the frontal band.

Question 13

The emerging layered cloud develops on the

Answer 13

cold side of the front, just ahead of the triggering upstream perturbation

Question 14

the first satellite indication of surface cyclogenesis

Answer 14

emerging layer cloud

Question 15

…………………………………….. is where the surface cyclone center is found

Answer 15

Under this emerging cloud and a little into the frontal band

Question 16

Comma Cloud

Answer 16

A cloud formation often seen in mid-latitudes takes the shape of a comma

Question 17

The exact shape of the comma depends upon

Answer 17

the wind flow into the comma and the stage of development of the system

Question 18

The head is

Answer 18

the main area of clouds and upward vertical motion.

Question 19

The cusp is

Answer 19

located near the center of rotation or the mid-level vorticity maximum.

Question 20

The tail

Answer 20

extends equatorward from the head, and during latter stages of the mid-latitude cyclone development is associated with the cold front.

Question 21

An upper level trough is placed on the

Answer 21

west side of the comma

Question 22

Cyclogenesis can occur in countless ways through

Answer 22

different orientations and relative strengths of the precursors.

Question 23

Based on the relative strengths of X and F (the upstream perturbation and frontal band or baroclinic zone, respectively), you can think of this as

Answer 23

a broad spectrum of cyclogenetic likelihood.

Question 24

a strong X needs

Answer 24

only a weak or no F to create a cyclone. In between, one can think of it as a balance between their relative strengths.

Question 25

a weak X requires

Answer 25

a strong F for cyclogenesis.

Question 26

As the absolute strengths of X and F increase, the

Answer 26

the sphere of influence of each element increases and the distance between them can be greater and still produce a cyclone

Question 27

In summer, since the synoptic-scale pattern is ................. cyclogenisis will occure when

Answer 27

weaker overall, cyclogenesis will occur when X and F are closer together on average than in winter.

Question 28

Case-1: X comparable to F Cyclogenesis

Answer 28

As X nears F, layered cloud (E) emerges from F ahead of X indicating cyclogenesis has begun, giving you a clue to the sphere of influence of X.  E emerges at or ahead of the inflection point on the poleward side of F when F becomes more S-shaped. E cools and expands further while cyclogenesis continues. It will then merge with the clouds associated with X to form a comma shape

Question 29

Case-2: Stronger F than X

Answer 29

When F is much stronger than X, the sphere of influence of X is small so it can be in close proximity to F where development will occur entirely within F. The presence of a strong, well-defined F in the satellite imagery means a strong baroclinic zone exists. With such strong thermal support, even a weak perturbation in the flow could be enough to cause cyclogenesis.

Question 30

Case-3: Stronger X than F

Answer 30

When X is stronger than F, X must have a large sphere of influence to develop into a cyclone. The development of cyclone which occurs from only X is conceptually shown below X is associated with a comma-shaped area of cloud/moisture upstream of F. There is no emerging cloud (E). This case, also known as "cold air cyclogenesis," has cyclone development occurring entirely within the cold airmass.