NWP Symposium

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The 1954 start of operational Numerical Weather
Prediction in Sweden




2
Why Sweden? -C. G. Rossby back from the US
1947 (home-longing, management and
politics) -Swedish state-of-art computers (BARK
1950, BESK 1953) -International support (from
the USA and Belgium)
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1953 BESK Binary Electronic Sequence Calculator
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BESK In 1953 the worlds best computer
Arithmetic unit
Electrostatic drum memory
Control desk
Williams tube memory
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The International Meteorological
Institute Rossby wanted, like V.
Bjerknes after WWI, to play an international role
in the political reconstruction after WWII

Steyer
Eady
Vuorela
Hubert
Rossby
V. Mieghem
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Baroclinic or barotropic models?
yes, but the large scale motion can
kinematically be described by a barotropic model
The atmospheric motions are driven by thermal
processes as reflected in baroclinic
developments
C. G. Rossby
R. C. Sutcliffe
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Common misinterpretations of Rossbys barotropic
concept -Only valid for stationary waves -Can
only perform linear extrapolations -Only valid
for barotropic features -Group velocity.
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The concept of group velocity tells us that any
boundaries have to be placed far enough away
from the verification region
24-hour compu- tational areas for - MISU - UKMO
9
A 24 hour forecast from the UKMO system winter
1953-54
Boundary errors and numerical instability
10
Only in 1965 did the UKMO go operational with NWP
after a personal intervention by the new Director
General John Mason
Dear members of the press, radio and TV...
Oh dear...
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In Stockholm tendency calculations were carried
out, first by hand in 1952, later on BESK in
1953 The Swedish tabloid Expressen
published the results almost a year before
Tellus (forecast left, analysis right)
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Barotropic re-run of the tree-feller storm the
2-3 January 1954
2 January 1954 00 UTC
24 h baro- tropic forecast
3 January 1954 00 UTC
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First real time NWP in late September
1954
Not quite the 72 hour computational area


72 hour verification area
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From the operational period Dec 1954-May 1955
-Professor Dahlqvist, when is Spring coming?
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-Tomorrow at 2 pm!
72 hours
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and Spring came!
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Why Sweden succeeded -C. G. Rossby back from
the USA 1947 -Swedish state-of-art computers
-International support -Choice of barotropic
model (skilful and providing operational
experience) -Efficient automatic analysis system
(Bergthorsson-Döös, 1955) -Not too small NWP area
(but not too big either, avoiding retrogression
of the planetary waves!)
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From wheat to bread! Bert Bolin shows automated
500 mb forecasts for Ragnar Fjørtoft (Norway) and
George Corby (UK) around 1956