Unit 4: Synoptic maps Flashcards
What is a synoptic map?
It is a summary of weather conditions over a particular time
Where is this information gathered?
From weather stations on Marion or Gough islands or airplanee, satellite images, weather balloons, floating weather buoys
How often are the maps updated?
Every 6 hours
How does air move in a high pressure cell?
The air descends (sinks) in an anti-clockwise direction while moving outwards (divergence)
How does air move in a low pressure cell?
The air acsends (rises) in a clockwise direction while moving inwards (convergence)
What is another name for a HP cell?
Anti-cyclone
What is another name for a LP cell?
Cyclone or depression
What are the names of the 3 HP cells that dominate SA?
South Atlantic high pressure cell, South Indian high pressure cell, Kalahari high pressure cell
What is an isobar?
It is a line joining places of equal pressure at sea level
What is air pressure measured in?
Hectopascals (hPa)
What size the isobar interval?
4 hPa
How is a trough formed?
When the isobars bend out around a LP cell
How is a ridge/wedge formed
When the isobars bend out around a HP cell
What is the area between two HP cells known as?
A saddle
What are the symbols for the three types f fronts?
Cold front - a line with triangles
Warm front - a line with semi-circles
Occluded front - blue line with interchanging triangles and semi-circles
What is an automatic station model represented by?
A circle in an triangle
Weather symbols: rain
dot
Weather symbols: drizzle
apostrophe
Weather symbols: showers
upside down triangle
Weather symbols: hail
triangle
Weather symbols: snow
asterixis
Weather symbols: thunderstorm
☈
Weather symbols: fog
three horizontal lines
Weather symbols: mist
two horizontal lines
Weather symbols: tropical cyclone
6 and 9 combined
What is the symbol for a normal station model?
a circle with a line pointing in the wind direction that has “feathers” that show the wind speed. On the left of this there is the maximum temperature then the type of precipitation then the dew point.
How is wind direction named?
It is named according to the direction it blows from
What is wind speed measured in?
Knots
How is cloud cover shown?
⅛ - circle with a dot in the middle
²∕₈ - circle with a quarter outlined
⅜ - circle with a half outlined and cut in half
⁴∕₈ - circle half colored in
⅝ - circle with half colored in and a horizontal line
⁶∕₈ - circle with three quarters colored in
⅞ - fully colored in circle but with a square missing in the middle
⁸∕₈ or overcast - fully colored in circle
Sky obscured by something other than clouds - circle with an x over it
How is wind speed shown?
By the feathers on the end of the wind direction line
two circles - calm no feathers - 1-2 one short feather - 5 one long feather - 10 one short and one long feather - 15 two long feathers - 20 two long feathers and one short feather - 25 three long feathers - 30 triangle - 50 triangle, one long feather and one short feather - 65
What does a typical summer map look like?
Interior is dominated by a LP Trough
Sub-tropical HP belt has shifted south
There is a tropical cyclone off the east coast
The frontal system are too far south to affect the weather of Western Cape
Station models show higher temperatures
The dates show summer months (Dec. - Feb.)
What does a typical winter map look like?
Interior is dominated by a Kalahari HP
Sub-tropical HP belt has shifted north
Station models indicates clear skies over interior
The frontal system are bringing rain to Cape Town
Station models would show lower temperatures
The dates show winter months (June - Aug.)
