NWP SymposiumUniversity of Maryland June 2004

The 1954 start of operational

Numerical Weather Predictionin

Sweden

NWP SymposiumUniversity of Maryland June 2004

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)

NWP SymposiumUniversity of Maryland June 2004

1953 BESK=Binary ElectronicSequence Calculator

NWP SymposiumUniversity of Maryland June 2004

BESK

In 1953 the world’s “best” computer

Electrostatic drum memory

“Williams tube” memory

Control deskArithmetic unit

NWP SymposiumUniversity of Maryland June 2004

The International Meteorological Institute

Rossby wanted, like V. Bjerknes after WWI, to play an international role in the political reconstruction after WWII

Eady

V. Mieghem

Rossby

Steyer

HubertVuorela

NWP SymposiumUniversity of Maryland June 2004

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

R. C. Sutcliffe C. G. Rossby

NWP SymposiumUniversity of Maryland June 2004

Common misinterpretations of Rossby’s barotropic concept

-Only valid for stationary waves

-Can only perform linear extrapolations

-Only valid for barotropic features

-Group velocity….

NWP SymposiumUniversity of Maryland June 2004

The concept of group velocity tells us The concept of group velocity tells us that any boundaries have to be placed that any boundaries have to be placed far enough away far enough away from the verification from the verification regionregion

24-hour compu-tational areas for

- MISU- UKMO

NWP SymposiumUniversity of Maryland June 2004

A +24 hour forecast from the UKMO system winter 1953-54A +24 hour forecast from the UKMO system winter 1953-54

BoundaryBoundaryerrors anderrors andnumericalnumericalinstabilityinstability

NWP SymposiumUniversity of Maryland June 2004

Only in 1965 did the UKMO go operational with NWP aftera personal intervention by the new Director General John Mason

Oh dear...

Dear members of thepress, radio and TV...

NWP SymposiumUniversity of Maryland June 2004

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)

NWP SymposiumUniversity of Maryland June 2004

+24 h baro-+24 h baro-tropic forecasttropic forecast 3 January 1954 00 UTC3 January 1954 00 UTC

2 January2 January1954 00 UTC1954 00 UTC

Barotropic re-run of the “tree-feller” Barotropic re-run of the “tree-feller” storm the 2-3 January 1954 storm the 2-3 January 1954

NWP SymposiumUniversity of Maryland June 2004

First real time NWP in late September 1954

Not quite the 72 hour computational area

72 hour verification area

NWP SymposiumUniversity of Maryland June 2004

-Professor Dahlqvist,when is

Spring coming?

From the operational period Dec 1954-May 1955

NWP SymposiumUniversity of Maryland June 2004

-Tomorrow at 2 pm!

+72 hours

NWP SymposiumUniversity of Maryland June 2004

…and Spring came!

NWP SymposiumUniversity of Maryland June 2004

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!)

NWP SymposiumUniversity of Maryland June 2004

From wheat to bread! Bert Bolin shows automated 500 mb forecasts for Ragnar Fjørtoft (Norway) and George Corby (UK) around 1956