Flashcards in Synoptic Charts Deck (24)
What is synoptic meteorology?
Study of pressure pattern charts
What is an air stream?
Flow of air from one region to another
What are warm air streams?
Warm air streams come from a warm source region and generally have a northerly component. ( Flowing in a southerly direction)
Latitudinal cooling of the surface layer (while the upper layers remain warm) may generate inversions and stable conditions
What are cold air streams?
Cold air streams flow from a cold source region to a warmer one. In the southern hemisphere cold streams generally have a southerly component ( Flowing in the northerly direction) As air flows north latitudinal heating warms the surface layers of the stream, while the upper layers stay cool. This results in steep environmental lapse rates and unstable conditions
What is the inter tropic convergence zone?
Boundary between airstreams originating in the northern and southern hemisphere and is found near the equator
What are highs associated with? (Anticyclones)
Subsidence and subsidence inversions.
-This limits vertical cloud development and generates stable conditions
- Visibility may be poor due to pollutants trapped beneath inversion
Weather conditions present with highs?
- Poor visibility
-Stratiform in lower layers
-Winds light and variable near center and blowing anticlockwise around the high
- In friction layer wind tends to blow out across isobars slightly, as friction slows the wind speed and reduces Coriolis effect
- Aloft winds end to be gradient (blowing parallel to isobars
What are lows associated with? (Depressions)
Rising air or convection
Weather conditions associated with lows?
- Instability often brings cloud and rain
-Visibility usually good
-Winds circulate clockwise around a low
-Slightly across the isobars and in near the surface
-Isobar spacing is usually closer around a low compared to a high
What is a col?
A col is a neutral area between two highs and two lows.
Winds are usually light and variable with poor visibility
What are streamlines?
Can be used in place of isobars on synoptic chart. Streamlines show average wind direction but do not indicate wind strength.
What is a tropical cyclone?
Intense low pressure area with wind speed greater than gale force.
What is gale force?
Where does a tropical cyclone derive its energy from?
Heat stored in tropical waters and from the release of latent heat during condensation and cloud formation.
Where do cyclones form?
Usually within 5-15 degrees north or south of the equator
They rarely form within 5 degrees of the equator due to the lack of Coriolis force to sustain cyclonic flow.
Four stages of a cyclone?
Explain the Formative stage of a cyclone...
An existing depression deepens
Wind speed reaches gale force
The eye forms
Characteristics of the eye of a cyclone?
Calm area in the middle of cyclone
Explain the Immature stage of a cyclone....
Pressure falls below 1000HPA
Winds reach hurricane force
Spiral bands form
Storm area still relatively small (30-50km radius)
What is hurricane force?
Explain the mature stage of a cyclone...
Pressure is steady
Area of storm expands
Hurricane force can extend 300km from eye
Where is the most destructive area of a cyclone?
in the southern hemisphere the most destructive area of a cyclone is the front left quadrant of the cyclone
Explain the decaying stage....
Pressure begins to rise
Storm area contracts
If land is encountered, cyclone weakens into rain depression
As cyclone moves inland wind and rain generally decrease