Meteorology 301
Laboratory Exercise 3
Surface Weather Observations (METARS) and Frontal
Analysis
Insert in ringed-three hole binder. Work not
turned in in binder will not be accepted.
Point deductions for sloppy or late work.
I. Introduction
A careful analysis of surface data is one of the most important techniques the
operational meteorologist can master. Since most users of weather
information or forecast services live at sealevel, it is obvious that a an
accurate portrayal of present conditions at that elevation is fundamental.
II. METAR decoding
The surface data is coded on the basis of international convention.
Observations are made hourly, and each "observer" is given a ten minute
time window, between 10 minutes before the hour to the hour to make the
mandatory surface observation. Any unusual conditions or events that occur
out of the time window mandate that a "special" observation be taken. These
reports are called "Metars".
The word METAR is from the French, "message d’observation
météorologique régulière pour l’aviation," and is thought to have originated
as a contraction from MÉTéorologique ("Weather") Aviation Régulière
("Routine"). The Federal Aviation Administration (FAA) may consider it to
be erroneous to abbreviate METAR as METeorological Airport
Report.[citation needed] The FAA and National Oceanic and Atmospheric
Administration (NOAA) specifically define a METAR as an "aviation
routine weather report," an approximate translation of the French.
Once the observations are plotted on a map, they can be contoured carefully,
as you did in the first part of the lab. It is important to keep in mind that a
careful analysis of these observations is critical. Not only does such an
analysis yield positions of low and high pressure areas, and troughs and
ridges, but because a diagnosis of the patterns on such analyses can yield
clues about weather development. For example, surface boundaries
(cold/warm air, high humidity/low humidity, wind shift or trough lines) are
often foci for the formation of thunderstorms, frontal waves etc.. Only an
accurate analysis of the surface data can disclose these important features.
We will "pretend" that each student has obtained the METARS for 12 UTC 3 February
2012 and plotted them on the surface chart you analyzed in Lab 2. But for practice in
learning the METAR code, you will decode a number of Kansas METARS for 05 UTC 3
February 2012.
III. Synoptic-scale Analysis
It is important that the beginning meteorologist accept the following:
although objective (computer) analysis of weather data has provided an
important service to operational meteorology, it is not a substitute, by any
means, for hand analysis. Even at the synoptic scale, computer analyses
tend to oversmooth ALL (even meteorologically-significant) smaller-scale
irregularities in the pressure field, often obscuring the important boundaries
alluded to in the last paragraph. In addition, the smoothing-procedure
(discussed in class) often results in isobars being drawn incorrectly with
respect to station data. Meteorologists who have experience in making field
operational decisions WILL NEVER exclusively depend upon machinegenerated analyses and will always complete an analysis of the data (even if
it is a "quick and dirty" analysis) themselves.
In reality, there are many facets to the manual analysis of surface data.
Some of the more difficult tasks, including the more detailed technical
aspects of frontal analysis, will be left to future classes (Metr 430).
The techniques we will center upon include:
A. Establishing a Synoptic History
In order to provide onself with guidance about what the present analysis
should basically look like, the analyst MUST examine the series of analyzed
surface maps preceding the synoptic time of the data to be analyzed.
Pressure systems should maintain some continuity, that is to say, should not
disappear from the map, should continue to intensify or weaken (depending
upon the trends determined from the recent "history" as depicted on the last
few maps) and should shift position in smooth arcs. Normally an analyst
will have also drawn the previous maps and will have some knowledge of
these prior conditions. For this lab, I will provide you with a couple of charts to
establish history.
B. Fronts
1. Surface warm, cold and stationary fronts are drawn on the warm-air
2.
3.
4.
5.
6.
side of packing in the surface isotherms. Classic surface
occluded fronts are found under the thickness tongue (as shown in a
future class) and join the cold and warm fronts at the triple point,
equatorward of which there is considerable packing of the thickness
arrows.
Fronts are found in regions of locally reduced pressure (sharp troughs
evident as kinks on isobars)
Usually (but not always) sharp wind shifts (veer of wind from warm
air side to cold air side of fronts) occur
Usually, pressures fall markedly ahead of fronts and rise behind.
7. 5. A first guess at frontal positions should be made on the basis of the history and
a synoptic-scale analysis of the thickness field (explained below and in class).
C. Exercises
1. METAR Decoding
You are provided with portions of the Federal Meteorological Handbook 1
(the complete Handbook is available as a pdf). A sample METAR observation
and its decoded version can be found here and a short guide from the NWS here.
Decode the following METARs for stations in Kansas at 05 UTC 3 February
2012. The station identifiers can be found here.
KAAO 030454Z AUTO 12017G26KT 10SM FEW041 13/06 A2995 RMK
AO2 PK WND
14032/0441 SLP142
Location...........: KAAO
Day of month.......: 03
Time...............: 04:54 UTC
Report is fully automated, with no human intervention or oversight
Wind...............: true direction = 120 degrees; speed = 17 knots with gusts of
26 knots
Visibility: 10 Statute Miles
Cloud coverage.....: few (1 to 2 eighths) at 4100 feet above airport level
Temperature........: 13 degrees Celsius
Dewpoint...........: 06 degrees Celsius
Altimeter Setting: 29.95 inHg
Remark: Automated Station with Precipitation Sensor; Peak wind 140
degrees at 32 knots at 0441 UTC; Sealevel Pressure 1014.2 mb
KCFV 030452Z AUTO 12011KT 10SM BKN043 14/01 A3008 RMK AO2
SLP185
Location: KCFV
Day of month: 03
Time: 04:52 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 120 degrees, Speed: 11 knots
Visibility: 10 Statute Miles
Clouds: Broken sky , at 4300 feet above airport level
Temperature: 14 degrees Celsius
Dewpoint: 01 degrees Celsius
Altimeter Setting: 30.08 inHg
Remark: Automated Station with Precipitation Sensor; Sealevel Pressure
1018.5 mb
KWLD 030550Z AUTO 12018G30KT 10SM BKN027 BKN055 13/07
A2995 RMK AO2 PK WND
13030/0546
Location: KWLD
Day of month: 03
Time: 05:50 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 120 degrees, Speed: 18 knots, with Gusts of
maximum speed 30 knots
Visibility: 10 Statute Miles
Clouds: Broken sky , at 2700 feet above airport level
Clouds: Broken sky , at 5500 feet above airport level
Temperature: 13 degrees Celsius
Dewpoint: 07 degrees Celsius
Altimeter Setting: 29.95 inHg
Remark: Automated Station with Precipitation Sensor; Peak wind 130
degrees at 30 knots at 0546 UTC
KIAB 030455Z AUTO 11021G28KT 10SM FEW039 BKN130 12/06
A2994 RMK AO2 PK WND
11028/0447 PRESFR SLP139
Location: KIAB
Day of month: 03
Time: 04:55 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 110 degrees, Speed: 21 knots, with Gusts of
maximum speed 28 knots
Visibility: 10 Statute Miles
Clouds: A few , at 3900 feet above airport level
Clouds: Broken sky , at 13000 feet above airport level
Temperature: 12 degrees Celsius
Dewpoint: 06 degrees Celsius
Altimeter Setting: 29.94 inHg
Remark: Automated Station with Precipitation Sensor; Peak wind 110
degrees at 28 knots at 0447 UTC; Pressure falling rapidly; Sealevel Pressure
1013.9 mb
KPTT 030535Z AUTO 05013KT 10SM TS OVC060 06/05 A2993 RMK
AO2 LTG DSNT ALQS
Location: KPTT
Day of month: 03
Time: 05:35 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 050 degrees, Speed: 13 knots
Visibility: 10 Statute Miles
Clouds: Overcast sky , at 6000 feet above airport level
Temperature: 06 degrees Celsius
Dewpoint: 05 degrees Celsius
Altimeter Setting: 29.93 inHg
Remark: Automated Station with Precipitation Sensor; Distant lightning all
quadrants.
KDDC 030536Z AUTO 35014KT 4SM VCTS RA BR SCT016 SCT028
OVC038 07/06 A2996
Location: KDDC
Day of month: 03
Time: 05:36 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 350 degrees, Speed: 14 knots
Visibility: 4 Statute Miles
Weather: Rain
Weather: Mist
Clouds: Scattered , at 1600 feet above airport level
Clouds: Scattered , at 2800 feet above airport level
Clouds: Overcast sky , at 3800 feet above airport level
Temperature: 07 degrees Celsius
Dewpoint: 06 degrees Celsius
Altimeter Setting: 29.96 inHg
KGBD 030535Z AUTO 06018G23KT 10SM SCT006 OVC065 05/03
A2994 RMK AO1 LTG
DSNT SE
Location: KGBD
Day of month: 03
Time: 05:35 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 060 degrees, Speed: 18 knots, with Gusts of
maximum speed 23 knots
Visibility: 10 Statute Miles
Clouds: Scattered , at 600 feet above airport level
Clouds: Overcast sky , at 6500 feet above airport level
Temperature: 05 degrees Celsius
Dewpoint: 03 degrees Celsius
Altimeter Setting: 29.94 inHg
Remark: Automated with no precipitation sensor; Lightning to distant
southeast
KSLN 030530Z AUTO 03011KT 5SM +RA OVC033 07/03 A3002
Location: KSLN
Day of month: 03
Time: 05:30 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 030 degrees, Speed: 11 knots
Visibility: 5 Statute Miles
Weather: Heavy Rain
Clouds: Overcast sky , at 3300 feet above airport level
Temperature: 07 degrees Celsius
Dewpoint: 03 degrees Celsius
Altimeter Setting: 30.02 inHg
KGLD 030535Z AUTO 08013KT 4SM -SN BR BKN003 OVC008 01/01
A3002
Location: KGLD
Day of month: 03
Time: 05:35 UTC
Report is fully automated, with no human intervention or oversight
Wind: True direction = 080 degrees, Speed: 13 knots
Visibility: 4 Statute Miles
Weather: Light Snow
Weather: Mist
Clouds: Broken sky , at 300 feet above airport level
Clouds: Overcast sky , at 800 feet above airport level
Temperature: 01 degrees Celsius
Dewpoint: 01 degrees Celsius
Altimeter Setting: 30.02 inHg
2. Surface Frontal Analyses
In this exercise, you will be recontouring the surface chart and 500 mb charts for 1200
UTC 3 February 2012. You are also provided with the 0000 UTC and 0600 UTC surface
analyses from the Hydrometeorological Prediction Center (HPC) to establish a history
and continuity. You are also provided with the 1200 UTC 3 February 2012 equivlaent of
nam_maps nam_thick from our lab, which is an overlay of the 1000-500 mb thickness
field on surface isobars.
Please use proper color conventions.
Procedure:
 Sketch frontal positions in lightly on acetate on the basis of the steps
above.
 Now draw isobars to fit the frontal position.
 Once frontal positions are finalized, make sure isobars KINK AWAY
from low pressure, as shown in class.
Charts


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

Surface plot for 12 UTC 3 February 2012
Analyzed 500 mb Height map for 12 UTC 3 February 2012
HPC Surface Analysis for 0000 UTC 3 February 2012
HPC Surface Analysis for 0600 UTC 3 February 2012
Surface Isobars with 1000-500 mb Thickness for 12 UTC 3 February 2012: Colorized and
Black/White
The steps involved in this lab include reanalyzing the surface chart for isobars, but adding
fronts.
a. Examine the history charts to see how HPC analyzed the history of this disturbance.
Careful...do not use "argument by authority", assuming that their analyses are correct.
Now write a paragraph or two of discussion on what the analyses depict for the cyclone
you found in Lab 2 over the southern Great Plains.
b. Perform an advection/frontal analysis on the 12 UTC charts (nam_thick)
showing 1000-500 thickness and surface isobars and isotherms (discussed
below) on the 500 mb Analysis for 1200 UTC February 2012. This will help
you in visualizing the position of actual fronts.


You will turn in a NEAT version of the frontal analysis , with advection arrows and fronts drawn
correctly;
To see the relationship of the thickness contours to the temperatures at 500 mb (to determine if the
gradients and location of cold and warm air masses is relatively the same) perform an isotherm
analysis on the 500 mb chart provided. Use acetate first, and draw contours at 5 degree C intervals
starting with 0, -5, -10 or 10, 15 etc.