Upper Air Charts

Upper Air Charts •  Before the Internet or AWIPS, DIFAX maps were the basic weather analysis and forecast charts used by meteorologists •  They were only available through a fax machine connected to a dedicated landline •  Currently, you can find charts on the internet, as well as through other weather analysis soFware (like AWIPS-­‐II) Surface Charts •  Analyzed charts issued every 3 hours (00Z – 21 Z) •  Data includes –  Hourly synopSc staSons –  Ship reports –  Buoy reports •  Maps can be found from the WPC: hVp://www.wpc.ncep.noaa.gov/ Surface Charts •  Isobar analysis: –  4 mb increments labeled with tens and units digits –  Lows and Highs labeled with L and H with the pressure value labeled nearby (in whole mb) •  Frontal Analysis hVp://www.wpc.ncep.noaa.gov/html/fntcodes2.shtml •  Used for current depicSon of surface weather features (most valuable weather chart) Upper Air Analysis •  Generated every 12 hours with 00Z and 12Z data •  Produced from the NAM Model analysis –  The NAM Model uses a first guess from the previous model run 6 or 12 hours earlier as a basis for construcSng the analysis fields –  Data is incorporated into the first guess field and the analysis is created via OpSmal InterpolaSon (OI) or 4-­‐D Data AssimilaSon –  Actual data is ploVed on the chart, but may not agree with chart’s analysis field 850 mb Chart •  Isoheights (solid contours) –  30 m intervals with 1500 m (150 decameters) reference line –  Contour labels in decameters –  PloVed heights are in meters •  Isotherms (dashed contours) –  5C intervals with 0C as reference line 850 mb Chart •  Uses: –  Low level jets –  Lower tropospheric temperature advecSon and thermal profile (thermal ridges and troughs) –  Lower tropospheric moisture advecSon and profiles (moist and dry tongues) 700 mb Chart •  Isoheights (solid contours) –  30 m intervals with 3000 m (300 decameters) reference line –  Contour labels in decameters –  PloVed heights are in meters •  Isotherms (dashed contours) –  5C intervals with 0C reference line 700 mb Chart •  Uses: –  LiFed moisture as a proxy for rising air –  Subsiding dry air as a proxy for downward moSon –  Elevated tropospheric moisture advecSon and profiles –  Mid-­‐tropospheric temperature advecSon and thermal profile –  Height changes 500 mb Chart (North America) •  Isoheights (solid contours) –  60 m intervals with 5400 m (540 decameters) reference line –  Contour labels in decameters –  PloVed heights are in decameters •  Isotherms (dashed contours) –  5C intervals with 0C reference line 500 mb Chart (North America) •  Uses: –  Mid-­‐tropospheric temperature advecSon and thermal profile –  Mid-­‐tropospheric moisture profile –  Wave paVern in the westerlies •  ID of longwaves and shortwaves –  LND and approximate steering level for surface synopSc systems –  Height changes and wave moSon –  VerScal and horizontal Slt of waves 500 mb Chart (Hemispheric) •  Contains same contours as the 500 mb North American analysis, except void of data plots •  AddiSonal Uses: –  Circumpolar vortex –  Planetary wave number and paVern –  Wave ID 300 mb Chart •  Isoheights (solid contours) –  120 m intervals with 9000 m (900 decameter) reference line –  Contour labels in decameters –  PloVed heights in decameters •  Isotachs (light dashed contours) –  20 knot intervals with 10 knot reference line –  SSppled regions represent: •  70-­‐110 knot winds •  150-­‐190 knot winds 300 mb Chart •  Uses: –  Polar jet stream locaSon/configuraSon/intensity –  4-­‐quadrant jet/divergence relaSonship –  Upper tropospheric wave paVern –  Regions of difluence and confluence –  Regions of upper-­‐tropospheric verScal shear 200/250 mb Chart •  Uses: –  Subtropical jet stream locaSon/configuraSon/
intensity –  4-­‐quadrant jet/divergence relaSonship –  Upper tropospheric wave paVern –  Regions of difluence and confluence –  Regions of upper-­‐tropospheric verScal shear 1000-­‐500 Thickness / MSLP Chart •  Thickness Values (usually dashed contours) –  VerScal distance in m between 1000mb and 500mb pressure levels –  FuncSon of avg virtual temperature of 1000mb to 500mb layer –  Increments of 60 gpm •  MSLP (solid black contour) 1000-­‐500 Thickness / MSLP Chart •  Uses –  Temperature advecSon •  Thickness is proporSonally to temperature •  Use MSLP contours as proxy for wind (assume geostrophic –  5400 (540) line generally divides polar air from mid-­‐laStude air (rain-­‐snow line) General Rules For Drawing Contours (see handout for more detail) •  Contour lines are drawn to idenSfy constant values of an atmospheric variable •  A contour is drawn through the staSon locaSon only if the data for that staSon has the exact value of the contour; otherwise, the contour is drawn between staSons •  Higher values are on one side of the contour and lower values on the other side of the contour •  Contours never cross or touch each other •  More than one contour of a given value may appear on a given map •  All contour lines must be clearly labeled •  OFen easiest to find the highest value or the lowest value and work from there •  Keep the surface wind in mind when drawing pressure contours. –  RelaSve to other staSons, the stronger the wind, the stronger the pressure gradient, thus the closer the isobars. 1016 mb H L 1016 mb H 1012 mb L 1016 mb H 1012 mb 1008 mb L 1016 mb H 1012 mb 1008 mb L 996 mb 1016 mb H 1012 mb 1008 mb L 996 mb 1000 mb 1016 mb H L 1012 mb 996 mb 1000 mb 1008 mb 1004 mb 1016 mb H L 996 mb 1012 mb 1000 mb 1008 mb 1004 mb