Surface Weather Maps L Symbol : Indicates an area of low air pressure (aka, pressure or pressure). Called a relatively barometric atmospheric cyclone Formation: As warm air in the center cyclone of a, surface pressure decreases. rises Air from surrounding areas replace moves in to it. Coriolis The effect produces a counterclockwise rotation incoming of these winds. In the Northern Hemisphere, winds curve to the of their point origin of. Coriolis The effect produces a counterclockwise rotation of these winds. In the Northern Hemisphere, winds curve to the of their point incoming right origin of. 1
Low Pressure in the Northern Hemisphere (top view) Feb 4 12:00 PM Low pressure systems have upward and spiraling winds. inward (top view) (side view) now draw in a second set of arrows -- ccw and inward As the air rises in a cyclone, it, cools, and forming clouds condenses precipitation and. Therefore, low pressure systems are "bad" associated with weather. expands Symbol : Indicates an area of high air pressure. H relatively 2
Formation: Sinking air at the center of a high pressure outward Air spirals from the center of a high pressure system. system causes surface pressure to. increase Coriolis The effect produces a clockwise rotation of these outgoing winds. High Pressure in the Northern Hemisphere In the Northern Hemisphere, winds curve to the of their point right origin of. Feb 4 12:00 PM (top view) As a result of the winds spiraling in the opposite direction of a cyclone, high pressure systems are called anticyclones. 3
High pressure systems have outward and spiraling winds. downward (top view) : (side view) draw in second set of arrows -- cw and outward As the air sinks in an anticyclone, it up, allowing relative humidity to, which results clear in skies and weather. Therefore, high pressure systems are good dry drop associated with weather. warms Isopleths equal Lines connecting values. Provides a quick and easy representation of weather patterns. Commonly used isopleths (lines of equal ) ( pressure) Mar 18 8:52 AM Mar 18 8:52 AM 4
Isopleths equal Lines connecting values. visual Provides a quick and easy representation of weather patterns. Commonly used isopleths (lines of equal ) ( pressure) Mar 20 7:20 AM Isopleths equal Lines connecting values. Provides a quick and easy representation of weather patterns. Commonly used isopleths Isotherms visual temperature (lines of equal ) Isobars barometric ( pressure) Mar 20 7:24 AM Isopleths Other types of isopleths Isodrosotherms ( ) dewpoints Isohumes ( ) Isotachs ( ) Isokeronics humidity windspeeds ( activity) Isohels T-storm INSOLATION ( duration of ) Isopleths Drawing isopleths can be difficult because observations are not made everywhere; therefore, gaps exist on surface weather maps and we must between recorded datapoints. interpolate 5
1. BE PATIENT General Rules for Drawing Isopleths 2. Use pencil (lightly at first) 3. If an interval is not provided for you, determine an appropriate interval. Ensure you pick an interval that will not result in too many or too few lines 68 54 72 65 63 57 1. BE PATIENT General Rules for Drawing Isopleths 2. Use pencil (lightly at first) 3. If an interval is not provided for you, determine an appropriate interval. Ensure you pick an interval that will not result in too many or too few lines 68 54 72 65 63 57 1. BE PATIENT General Rules for Drawing Isopleths 2. Use pencil (lightly at first) 54 65 63 57 3. If an interval is not provided for you, determine an appropriate interval. Ensure you pick an interval that will not result in too many or too few lines 68 72 4. Draw smooth lines 68 54 72 65 63 57 Next slide for an example... Mar 18 9:01 AM General Rules for Drawing Isopleths 5. Isopleths can form closed loops; however, they must NEVER one another. 6. Isopleths should not branch or fork. 7. Isopleth lines must be labeled with their value 30 20 10 cross 20 30 10 30 20 10 General Rules for Drawing Isopleths 8. When you are finished, check your results. One way to do this is to imagine that you are walking along an isopleth. The values of the data points on one side of that isopleth line should be greater than the isopleth value and values of the data points on the other side should be less than the value of the isopleth. Remember to interpolate! Data points that are close in value to the isopleth line you are drawing will require you to draw your line closer to them. 6
54 65 63 57 Draw the isotherms for 40, 50, 60 & 70 degrees 68 72 Mar 18 9:01 AM Mar 31 4:17 PM Isobars high Used to identify areas of and/or low pressures. Draw isobars at 4 mb intervals (starting at 1008 mb) Draw isobars at 4 mb intervals (starting at 1008 mb) Isobars high Surface winds blow from to low pressure perpendicular centers and are to the isobars. 7
Draw isobars at 4 mb intervals (starting at 1008 mb) Isobars faster The closer the isobars are to one another, the the change in pressure (the higher the pressure gradient stronger or rate of change) and the the winds. Also, the greater the difference between the high and low pressures the stronger the winds. Pg. 1 of ESRT 1. Find the pressure gradient between B and C. miles 0 10 20 30 40 1. Find the pressure gradient between B and C. 2. Find the pressure gradient between D and E. miles 0 10 20 30 40 Mar 21 7:17 AM Mar 21 7:17 AM 2. Find the pressure gradient between D and E. Isobars faster The closer the isobars are to one another, the the change in pressure (the higher the pressure gradient stronger or rate of change) and the the winds. Also, the greater the difference between the high miles 0 10 20 30 40 and low pressures the stronger the winds. Mar 21 7:17 AM 8
General Weather Patterns Overall, weather patterns tend to follow the direction of the upper level prevailing winds and the jet stream. The United States are located in the prevailing westerlies global global wind belt. Add to notes: the 'normal' storm track from the SW to the NE dashed General Weather Patterns A line with an at the end may be used to show the direction of a weather system. general arrow General Weather Patterns However, regional weather conditions are influenced by cyclone and winds local and surface winds blowing from high to low pressure areas. anticyclone 9
Scales of Motion Global Scale Impacted by global prevailing winds Impacts weather events all year Macroscale Area influenced = Jet streams hemisphere Scales of Motion Synoptic Scale Area influenced = ~ area of a large state Typical weather duration = Associated weather events: Weather forecasts Hurricanes 2-3 days Scales of Motion Mesoscale Area influenced = ~ area of a county Typical weather duration = Associated weather events: Thunderstorms 24 hours Microscale Scales of Motion Area influenced = Typical weather duration = Associated weather events: Dust devils ~ area of a city block current Tornados Which direction are the winds rotating? Find the center of the LOW pressure center: L 10
Draw in the occluded, cold, and warm fronts with proper symbols: 11