History of Forecasting 1

A History of Modern Weather
The Beginning: Weather Sayings
"Red Sky at night, sailor's delight. Red sky in the morning, sailor take
"Mare's tails and mackerel scales make tall ships take in their sails."
"Clear moon, frost soon.”
"Halo around the sun or moon, rain or snow soon."
"Rainbow in the morning gives you fair warning."
"When the stars begin to huddle, the earth will soon become a puddle."
By the late 1700s, reasonable
(sufficiently precise and repeatable)
weather instruments became available
More and more people took
observations….and some early
networks were started
Early Networks
• 1792 the Mannheim (or Palatine) network included 39 stations
from France, Germany, Italy, Scandinavia, Poland and Russia.
• In the United States a formal observation program was
initiated in l816 under the auspices of the surgeon-general of
the army; army surgeons were required to take three
observations per day of pressure, temperature, state of sky and
• By 1853 nearly 100 army posts were providing such daily
• Other American networks were organized under the auspices
of the Navy and the Smithsonian Institution.
The First Weather Forecaster?
The problem: no way to rapidly
communicate weather
• This changed around 1845 with the
invention of the telegraph
First Real-Time Weather Maps
“Ol Probs”
Probabilities”), who led the
establishment of a weather
forecasting division within the
U.S. Army Signal Corps.
•Produced the first known
communication of weather a
weather forecast (including the
term “probability”).
Professor Cleveland Abbe, who issued the first public
“Weather Synopsis and Probabilities” on February 19,
On May 7, 1869, Abbe proposed to the Cincinnati
Chamber of Commerce "to inaugurate such a system, by
publishing in the daily papers, a weather bulletin, which
shall give the probable state of the weather and river for
Cincinnati and vicinity one or two days in advance”.
Cleveland Abbe released the first public weather
forecast on September 1, 1869.
Following the signing by President Ulysses S. Grant of
an authorization to establish a system of weather
observations and warnings of approaching storms, on
February 19, 1871, Abbe issued the first “official”
public Weather Synopsis and Probabilities based on
observations taken at 7:35 a.m.
An early example of a report:
"Synopsis for past twenty-four hours; the barometric
pressure had diminished in the southern and Gulf
states this morning; it has remained nearly stationary
on the Lakes. A decided diminution has appeared
unannounced in Missouri accompanied with a rapid
rise in the thermometer which is felt as far east as
Cincinnati; the barometer in Missouri is about fourtenths of an inch lower than on Erie and on the Gulf.
Fresh north and west winds are prevailing in the
north; southerly winds in the south. Probabilities
[emphasis added]; it is probable that the low pressure
in Missouri will make itself felt decidedly tomorrow
with northerly winds and clouds on the Lakes, and
brisk southerly winds on the Gulf."
Weather Prediction Technology
of the Late 1800s
• The essential approach…simple temporal
• No fronts, but they understood that
discontinuities existed.
• Little understanding of the evolution of
weather systems.
Atmospheric “Model”
Shaw Forecasting Book 1911
The Next Major Advance
• The Norwegian Cyclone Model, around
Norwegian Cyclone Model
• Provided a coherent consistent picture of
airflows, clouds, and precipitation of
cyclones and fronts
• Provided a model for frontal and cyclone
evolution, aiding future prediction.
Beginning of Reliable Upper Air
• The first true radiosonde that sent precise
encoded telemetry from weather sensors
was invented in France by Robert Bureau.
Bureau coined the name "radiosonde" and
flew the first instrument on January 7, 1929.
1940s: Upper Air Charts Became
• Gave a 3D picture of what was happening
• Upper flow steered storms, and thus
provided a tool for forecasting cyclone
Summary I
• Prior to approximately 1955, forecasting was
basically a subjective art, and not very skillful.
• The technology of forecasting was basically
subjective extrapolation of weather systems, in the
latter years using upper level flow.
• Local weather details—which really weren’t
understood-- were added subjectively.
The Development of NWP
• Vilhelm Bjerknes in his
landmark paper of 1904
suggested that NWP was
– A closed set of equations
existed that could predict
the future atmosphere
(primitive equations)
– But NWP wasn’t practical
then because there was no
reasonable way to do the
computations and sufficient
data for initialization did
not exist.
L. F. Richardson: An Insightful
But Unsuccessful Attempt
• In 1922 Richardson
published a book
Weather Prediction by
Numerical Process that
described an approach to
solving the primitive
equations: solving the
equations on a grid using
finite differences.
L. F. Richardson
• He attempted to make a numerical forecast using a
mechanical calculator
• Unfortunately, the results were not good, probably
because of problems with his initial conditions.
L. F. Richardson
• He imagined a giant theater filled with
human calculators…
• So NWP had to wait until a way of doing
the computations quickly was developed
and more data…especially aloft… became
NWP Becomes Possible
• By the mid to late 1940’s there was an
extensive upper air network, plus many
more surface observations. Thus, a
reasonable 3-D description of the
atmosphere was possible.
• Also during this period digital
programmable computers were becoming
available…the first..the ENIAC
The Eniac
The Last Piece of the Puzzle
• Meteorologists realized that useful
numerical weather predictions were
possible using a simplified equation set that
waseasier to solve.
• The Barotropic Vorticity Equation
(conservation of absolute vorticity) was
suggested as a first step
First NWP
• The first successful numerical prediction of
weather was made in April 1950, using the
ENIAC computer at Maryland's Aberdeen
Proving Ground
• The prediction was for 500 mb height,
covered North America, using a twodimensional grid with 270 points about 700
km apart.
• The results showed that even primitive
NWP was superior to human subjective
prediction. The NWP era had begun.
Evolving NWS
• Early 50s: one-level barotropic model
• Late 50s: Two-level baroclinic QG model (just
like Holton!)
• 1960s: Primitive equation models of increasing
resolution and number of levels.
• Resolution increases (distance between grid points
decrease): 1958: 380 km, 1985: 80 km, 1995: 40
km, 2000: 22 km, 2002: 12 km
NWP Improvements in the Later
20th Century
• Better resolution
• Rapidly increasing data for initialization
from weather satellites, radars, more surface
observations, and other sources.
• Better models: better numerics and physics
Forecast Skill Improvement
NCEP operational S1 scores at 36 and 72 hr
over North America (500 hPa)
National Weather Service
S1 score
"useless forecast"
36 hr forecast
72 hr forecast
Error 35
10-20 years
"perfect forecast"
The Advent Of Statistical PostProcessing
• In the 1960s and 1970s, the NWS developed and
began using statistical post-processing of model
output…known to most as Model Output
• The idea: models have systematic biases …why
not remove them based on past performance?
• Also, might be able to statistically add the effects
of local features not resolved by the model.
• Based on linear regression: Y=a0 + a1X1 +
a2X2+ a3X3 + …
• MOS is available for many parameters and
time and greatly improves the quality of
most model predictions.
The computers models become
capable of simulating/forecasting
local weather.
As the grid spacing decreased to 15 km and
below… it became apparent that many of
the local weather features could often be
simulated and forecast by the models.
80 km,
NGM, 1995
2001: Eta Model, 22 km
12-km WRF-AR
are similar
December 3, 200
0000 UTC Initia
12-h forecast
3-hr precip.
4-km MM5