Surface Weather Observations (Worldwide, every 3 Hours GMT starting at 00:00) Current and past state of the weather e.g. Rain, Fog, etc. Air temperature Dry bulb temperature (Wet bulb temperature) Maximum, minimum temperatures

Surface Observations (continued) Relative humidity Amount and type of clouds Wind speed and direction Pressure, pressure tendency Precipitation

Clouds Aid in weather forecasting Trace atmospheric motions (e.g. satellite imagery) Produce precipitation Reflect sunlight away from Earth Absorb/emit heat radiation Absorb or rainout air pollution

Basic types of clouds High Mid-level Low

“Nimbo-” or “-nimbus” means cloud is producing precipitation. e.g. Cumulonimbus, Cb (thunderstorm) Nimbostratus, Ns (rain or snow)

Cirrus (Ci) clouds over the Golden Gate bridge Ci clouds over Germany

Altocumulus clouds over Edmundton, Alberta

Nimbostratus (Ns) cloud over Germany

Cumulus clouds in Victoria, Australia

Cumulonimbus (Cb) cloud near Hong Kong

Supercell thunderstorm in Australia

Clouds over Tucson

Wind Vane or Weather Vane Measures direction wind is blowing FROM

“Dove of Peace” by Joseph Rakestraw (1787)

Windmill anemometer measures wind speed and direction

Water barometers Berti (1639) in Rome Guericke (c1654) in Magdeburg

To make a mercury barometer, just fill a sealed tube with mercury then invert the tube in a container of mercury.

Mercury barometer

Tanker steam cleaned and closed, crushed when cooled off Empty bottle Opened at 2000m Crushed at sea level

Force (air pressure x area) UP is greater than weight of water DOWN

Weather glass or Thunder glass Used to measure CHANGES in atmospheric pressure (or temperature) "decreasing pressure predicts stormy weather"

Hurricane Wilma October 19, 2005 p = 882 mb

Location of the station on the map. The name of the location or airport abbreviation might be given nearby.

Air temperature in degrees Fahrenheit (°F)

Dew Point temperature in degrees Fahrenheit (°F) dewpt

A staff is rotated around the station. Wind direction A staff is rotated around the station. Temp dewpt Remember, winds are identified as the direction FROM which they come. This would be a west northwest wind or about 290º.

Attached to the staff are symbols for speed. Wind Speed Attached to the staff are symbols for speed. Temp dewpt

The coding for the wind speed symbols can be generalized as: half barb about 5 knots note, barb is on the back end of a wind direction arrow full barb about 10 knots these are additive for the total amounts three full barbs = 30 knots full flag = 50 knots 65 knots

Each pennant (filled triangle) = 50 knots[ Wind Speeds Each 1/2 flag knots = 5 knots Each full flag = 10 knots Each pennant (filled triangle) = 50 knots[

Current Barometric Pressure Temp dewpt pressure

Barometric Pressure is VERY important! average barometric pressure at sea level is 1013.25 mb. current barometric pressure is reported to the nearest TENTH BUT, in order to save space

average barometric pressure at sea level is 1013.25 mb, but actual barometric pressure varies around this value + about 30 mb = 1043 mb somewhat higher 1013.3 somewhat lower - about 30 mb = 983 mb

So they do not PLOT the beginning number or numbers 1013.3 ---- 13.3 x 133 they, also, do not PLOT the decimal point, but report to the nearest TENTH

Which would make the value most realistic? From the three numbers, you must INTERPRET whether the preceding value is 10 or 9 Which would make the value most realistic?

and then consider whether a 10 or a 9 Add the decimal point and then consider whether a 10 or a 9 makes the value NEAREST to an average pressure of 1013.25 mb

(1013.3 mb) What is the pressure? 084 08.4 1008.4 962 96.2 996.2 281 28.1 1028.1 987.5 875 87.5 322 32.2 1032.2

So, more information may be given and must be coded. Not only is the pressure itself important, but also the way the pressure has been changing. So, more information may be given and must be coded.

How has the barometer been changing? Temp dewpt pressure trend + it is higher now than in the past - it is lower now than in the past

How much the pressure has changed Temp dewpt pressure trend change the amount of change in the past three hours again, reported in TENTHS without the decimal

What has the pressure been doing? Shown diagrammatically Temp dewpt pressure trend change shown

graphic depiction of percentage of the sky covered by clouds Total amount of cloud Temp dewpt pressure trend change shown graphic depiction of percentage of the sky covered by clouds

about 60% no clouds about 10% about 75% about 25% about 80% Amount about 60% no clouds about 10% about 75% about 25% about 80% completely overcast about 40% sky obscured about 50%

Symbol positions to identify the cloud types Temp dewpt pressure trend change shown low clouds middle clouds high clouds Cloud types tell much about the weather conditions. The cloud types are identified by symbols, and classed as low, middle, and high clouds.

How much of the sky is covered by low and middle cloud cover? Temp dewpt pressure trend change shown low clouds middle clouds high clouds low or middle cloud cover What amount, in tenths, of the sky is covered by low or middle clouds. This is a coded number with the percentage close to the printed number.

What is the present weather? Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow low or middle cloud cover The current weather is very important. A detailed set of symbols provides weather descriptions.

Symbols for present weather

, * . Samples of present weather symbols. rain fog snow haze slight rain showers , thunderstorm drizzle . ice or snow pellets lightning cloud development not observed

Combining symbols tells more of the detail. intermittent rain, slight at time of observation continuous rain, slight at time of observation continuous rain, moderate at time of observation intermittent rain, moderate at time of observation intermittent rain, heavy at time of observation continuous rain, heavy at time of observation

100 different symbols provide details about the PRESENT WEATHER. (see Class Handout and http://www.srh.noaa.gov/jetstream/synoptic/sfc_plot_symbols.htm#ddff)

The visibility is especially important for pilots. Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibility low or middle cloud cover Visibility is given in miles and fractions

The past weather uses symbols. Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibility low or middle cloud cover PAST , *

Past Weather Symbols

Time precipitation began or ended Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibility low or middle cloud cover PAST when Coded for how many hours ago the precipitation began or ended. Again, the code is close to the number of hours.

Height of cloud base PAST Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibility low or middle cloud cover PAST when base Coded height of base of clouds. Important for pilots.

The amount of precipitation Temp dewpt pressure trend change shown low clouds middle clouds high clouds wxnow visibility low or middle cloud cover PAST when base amount Amount of precipitation is plotted in inches to the nearest hundredth of an inch.

Decode this station. 237 ,, 75 - 1 12 65 6 3 4 36

any low clouds. any middle clouds. any high clouds any low clouds? any middle clouds? any high clouds? amount of low and middle clouds height of cloud base visibility barometric pressure trend in pressure pressure three hours ago how has pressure changed present weather past weather when precipitation began/ended amount of precipitation yes yes 237 ,, 75 yes - 1 12 6 4 65 6 3 1 mile 4 36 1023.7 mb falling 1024.9 down then steady temperature dew point wind direction wind speed amount of sky cover 75 °F continuous slight drizzle 65 °F rain south 4 25 knots .36” 80%