Synoptic situation Modern Forecasts of 1953 storm(‘ReForecasting’)

Expand in three ways:• a) Barotropic Forecasts• b) Initial error hand vs present analysis (’53 data)• c) (nearly) Contemporary UK NWP for ’53 case• Acknowledge Anders Persson about point c.

The 1953 North Sea Gale in Perspective of Historical NWP efforts.

H. M. van den Dool, R.E. Kistler and S. Saha, at NCEP

Mean Sea Level Pressure Maps for Jan 29 – Feb 1, 1953, every 3 hours from NCEP-NCAR Reanalysis (Kalnay et al

1996; Kistler 2001

29/0

30/0

31/0

01/0

From Hay, R. F. M., and J. Laing, 1954: The storm of 31st January - 1st February 1953. Mar. Obs., 24, 87-91.

Height fields Jan 28 - Feb 1, 1953 every 6 hours (Reanalysis)

• To be sure: This disaster was not just meteorology1) Oceanography, wind stress effect, Kelvin waves and astronomical tides, wind waves2) ‘Coastal’ defense, and its maintenance3) Preparedness, warning system, protocol, bureaucracy, communications, evacuation4) Assessing the risk of a given surge forecast

Forecasts valid for Feb, 1, 1953, 3Z

• Reanalysis model T62L28

The previous map is a contemporaneous hand analysis, digitized at 2.5 by 2.5 grid. The

original looks like this:

Source: KNMI, F. H. Schmidt- editor,1960: Meteorologische en Oceanografische aspecten van stormvloeden op de Nederlandse kust. Bijdrage tot het rapport van de Deltacommissie door het KNMI. Staatsdrukkerij- en Uitgeverijbedrijf - ‘s Gravenhage. pp200.

Synoptic situation Modern Forecasts of 1953 storm

(‘ReForecasting’) by NCEP(several resolutions; ETA), ECMWF(several resolutions), Hirlam

Expand in three ways for Historical NWP

aspects:• a) Barotropic Forecasts• b) Initial error: hand-analysis vs Re-analysis (’53

data)• c) (nearly) contemporary UK NWP of ’53 case

dAVA (global barotropic) forecasts

/t (ζ’-λ2ψ’) = - Vn .ζ’ - V’. (ζn + f + ζ’) - D4 ζ’- K ζ’,

• where Vn and ζn refer to climatological mean flow, and ζ’ is ‘anomaly’ vorticity.

• T30L1• Cressman-Bolin correction applied to anomaly.

Parameter λ2 found thru adjoint study (Rinne et al 1993)

• 1980’s type barotropic model

Verification by numbers (Anomaly Correlation 500 mb

height)

65

70

75

80

85

90

95

100

A

nom

aly

Corr

ela

tion

26/12Z

27/12Z 28/12Z 29/12Z 30/12Z 31/12Z 01/12Z 02/12Z 03/12Z

Verifying Time

Skill of 36 hour dAVA forecastsdomain: 50W-30E and 40N-67.5N

65707580859095

100 A

nom

aly

Corr

ela

tion

26/12Z

27/12Z 28/12Z 29/12Z 30/12Z 31/12Z 01/12Z 02/12Z 03/12Z

Verifying Time

dAVA 36 hoursMRF 84 hrs

Skill of NWP forecastsdomain: 50W-30E and 40N-67.5N

20

40

60

80

100

z500 a

nom

aly

correla

tion

0 1224364860728496108120132144lead (hours)

dAVA

MRF

Forecasts verifying Feb, 01, 1953 03Z

On the initial error

• ‘hand’analysis minus Re-analysis is ~2mb/25gpm for MSLP/Z500 respectively. Atl-Eu domain for 1953 data.

• CDAS/Reanalysis (T62L28) has currently (Jan): 1.5mb/12.0gpm (0hr, fit to radiosondes) 1.8mb/18.1gpm (6hr, guess to obs) (EuroAtl)

It is (?) amazing that the initial error for 1953 Reanl, with so much less data than in 2004, is not even a factor of 2 larger.

INITIAL

30 jan 15Z

31 jan 15Z (anl)

+24 hr barotropic forecasts

QJ 1958

Analysis 31 Jan 15Z 1953, 500mb(ft)

+24 hr by Sawyer_Bushby model

24 hr forecast of 500mb height by Sawyer_BushbyModel, verifying Jan 31 15Z, Met Magazine1954

“If the Sawyer-Bushby forecast had been right, the calamity would have been a lot more

calamitous than it already was”. Free after ‘Discussion’(1954) and

Hinds(1981).

Water Level Forecast 12 Hours

Conclusions:• With current NWP models and analyses, but 1953

data, forecasts out to 2 (4) days appear possible. KNMI(1960) conclusion about lack of data

(easy scapegoat) is clearly overstated (for this case). • Accurate barotropic forecast are possible out to 30

hrs (i.e. after the bomb had developed)• Differences between hand analysis and Reanalysis

are ~ 2mb and 25gpm (1953 data coverage). Jan2003 CDAS errors are ~1.6mb/15gpm.

• There are a few early NWP efforts with regard to the storm of 1953. Jan 30/31 15Z was one of the canned cases used at UKMO. Bushby-Sawyer +24hr forecast was remarkable!

A KNMI initiated warning system, implemented in 1916 (following a previous flood)

Three options:1) Say nothing (benign circumstances)2) Warn for significantly enhanced water levels for the next two astronomical high tides (by region)3) Warn for dangerously enhanced water levels for the next one astronomical high tide.

Saturday Jan 31 at 10am: option 2 warning was issued Saturday Jan 31 17:15 (they had to wait until after the afternoon high tide, in order to ‘avoid confusion’): option 3 (for the first time in history)

(Warnings were issued to other authorities (supposedly they knew what to do), and to the public via radio at 18:00 onward. Note there was no radio after midnight. Zero communication during the disaster.)

RMS-errors of MRF(GFS) forecasts, and initial errors.

Z500

Lead — > 0 24 48 72 96 hr climo

------------------------------------------------------------------- 30 Jan 3Z 0(28) 24 43 57 96 140 31 Jan 3Z 0(27) 34 54 68 95 129 01 Feb 3Z 0(22) 24 57 73 108 137 gpm

MSLP

Lead — > 0 24 48 72 96 hr climo ------------------------------------------------------------- 30 Jan 3Z 0(1.8) 3.2 5.2 7.4 9.6 10.731 Jan 3Z 0(2.0) 4.1 6.7 8.1 7.4 12.8

01 Feb 3Z 0(2.4) 2.9 6.3 6.7 9.8 15.1 mbar