1. a.k.a: Surface Synoptic Chart
Surface Weather Map
a.k.a: Surface Synoptic Chart
ATMS 101 W2019

3. Available here: http://www.atmos.washington.edu/data/vmaproom/

4. Why Surface Weather Maps?
Summarizes weather conditions at the surface (where we are!)
Using a progression of charts can see how weather is evolving.
Summarizes our conceptional model of the atmosphere (fronts).

5. First Surface Weather Map
Created by H. W. Brandes in 1820 for March 6, 1783.
The arrows indicate wind direction and the lines show the deviation of pressure from average conditions

6. One of the weather maps created by Elias Loomis in his groundbreaking paper on the storms of February 1842.
Surface wind direction is indicated by arrows and the deviations from average pressure are shown by the dashed lines. Temperatures are indicated by dotted lines and the sky or precipitation type by the color shading. This map indicates a strong low-pressure center over the Ohio Valley, rain on the coast, and snow-laden northwesterly winds to the west.

7. The Telegraphic Communication Revolution
By 1849 a telegraphic network was organized in the United States for the transmission of daily meteorological observations for a collection of stations.
In England during the l851 World's Fair, there was a daily weather maps for display, and by 1859 the British Meteorological Department began to operationally distribute weather information using this new technology.
The internet of the 19th century

8. First Real-Time Weather Maps

9. The weather maps of the 1800s were missing something all maps have today: FRONTS

11. Fronts
The Norwegian Cyclone Model, around 1920

12. Fronts
Regions of enhanced temperature changes and major weather (clouds and precipitation)

13. 1950 Surface Weather Map

14. Still Used Today

15. What is on surface charts?
Station models: meteorological shorthand describing the observations at locations
Isobars (lines of constant sea level pressure)
Fronts and troughs (locations of low pressure)

16. Surface observations are plotted using the station model

17. Station Model
In the U.S., the station model uses temperatures in F; other countries used C
Sea level pressure. 3 digits in tenths of a hPa (mb).
Divide by 10 and add either 9 or 10.
237 > 23.7> hPa
When choosing between 9 and 10, use the one that gives one a reasonable pressure (hint: average SLP is around 1000 hPa)

18. Practice
198 is hPa, not hPa
745 is hPa, not hPa
247 is hPa, not hPa

19. Pressure Change over the Past 3 hr
Surface pressure change in tenths of hPa
Over past 3 hr.
3 means pressure increase of .3 hPa in last 3 hr.
Cartoon next to it.

21. Current Weather

22. Sky Coverage

23. Sky Obscured…you are in cloud

24. Wind Pennants

25. Wind Speed

26. Practice

27. Practice

28. You need to be able to read the station models

32. What kind of observations are plotted on surface charts?

33. ASOS: Automated Surface Observing System: Backbone Observing System in the U.S.: Mainly Airports

34. Hydrothermograph

35. Precipitation Gauges

36. Laser Weather
Identifier

37. Anemometer
Wind Vane
Laser Ceilometer

38. Full ASOS system in Arizona

39. Marine Reports

40. Ocean and Lake
Weather Buoys
Anchored

41. Drifting Buoys
Pressure
Wind

42. Coastal Marine (CMAN) Reports from the Coast Guard

43. Northwest Buoy and CMAN Locations

44. Ship Reports: Marine VOS Program
Volunteers Observers--generally 6-hourly reports
Highly variable quality and frequency

46. Isobars of sea level pressure are found on station map
Isobars are lines of constant or equal pressure
Everywhere along each line the pressure is the same
Labeled in hPa/mb (e.g., 996, 1000, 1004, etc)

47. Why use sea level pressure rather than station pressure—the pressure at the elevation of the barometer?
Because pressure decreases with height!
Thus, the pressure variations on weather maps would be dominated by terrain changes in station or surface pressure was plotted.

48. If station or surface pressure plottedH

49. Terrain effects on pressure would swamp the meteorological signal
So why not take the terrain effects of pressure out?
Adjust the station (surface) pressures to get the pressure at a standard level: sea level.
Called pressure reduction to sea level.
For example, near sea level, pressure drops about 1 hPa for every 8 meters in elevation.

50. Example of Pressure Reduction
* 1024 hPa
64 m
Sea Level
* 1032 hPa

52. Pressure Reduction
In reality, done in a more sophisticated way, but still somewhat artificial
Particular problems for high elevation stations
Sea level pressure is determined at all major observing locations and plotted in the station models.
But how make SL pressure maps?

53. Technique called isoplething
Isobars generally drawn every 4 hPa (e.g. 1000, 1004)

54. Once the analysis is done, put on H’s and L’s
High- “H” -high sea level pressure relative to the surroundings. Also known as a ridge. Generally associated with fair weather.
Low- “L” - low sea level pressure relative to the surroundings. Also known as a trough. Generally associated with cloudy, stormy weather.

56. Pressure patterns are very important because they influence winds
Strong winds are generally associated with strong horizontal pressure gradients, where pressure changes rapidly with distance.
Weak winds associated with weak pressure gradients
strong
weak

57. Winds and pressure
Near terrain winds tend to go directly from high to low pressure
Away from terrain, winds tend to parallel isobars, with a small angle towards lower pressure (you will learn why later!)

58. Will explain why in a few weeks
Surface wind H

59. In the northern hemisphere winds tend to blow counterclockwise around lows and clockwise around highs (opposite in the southern hemisphere)

60. Northern Hemisphere
clockwise
counterclockwise

61. New terms: cyclonic and anticylonic

62. Other features on surface charts

63. What are fronts?
The tropics are warmer than the Arctic/Antarctic regions.
But temperatures don’t change gradually between north and south.
There are regions of large horizontal temperature changes generally in the midlatitudes, which are known as fronts.
Fornts are located on the warm side of the zone of temperature change.

64. Definition
A front is a boundary between relatively uniform warm air and a zone in which temperatures cools rapidly

65. Front
Frontal
Zone
relatively uniform cool air
relatively uniform warm air

66. Fronts and Temperature

67. Four Main Types of Fronts

68. Warm Front

69. Stationary Fronts

70. Occluded Front (a hybrid)

71. Fronts and Pressure Fronts Tend to Be in Pressure Troughs

72. Fronts are associated with bands of clouds

73. Fronts are associated with precipitation