Transcript Document 7867368

The 1953 North Sea Gale in Perspective of Historical NWP efforts.
H. M. van den Dool, R.E. Kistler and S. Saha, at NCEP
•  Synoptic situation
•  Modern Forecasts of 1953 storm(‘ReForecasting’)
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 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.
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 meteorology
1) Oceanography, wind stress effect, Kelvin waves and
astronomical tides, wind waves
2) ‘Coastal’ defense, and its maintenance
3) Preparedness, warning system, protocol, bureaucracy,
communications, evacuation
4) 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
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M/Mt (ζ’-λ2ψ’) = - Vn .Lζ’ - V’.L (ζn + f + ζ’)
- DL4 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)
Skill of 36 hour dAVA forec
domain: 50W-30E and 40N-67.5N
Anomaly Correlation
100
95
90
85
80
75
70
65
26/12Z 27/12Z 28/12Z 29/12Z 30/12Z 31/12Z 01/12Z 02/12Z 03/12Z
Verifying Time
Skill of NWP forecasts
domain: 50W-30E and 40N-67.5
Anomaly Correlation
100
95
90
85
80
75
70
65
26/12Z 27/12Z 28/12Z 29/12Z 30/12Z 31/12Z 01/12Z 02/12Z 03/12Z
Verifying Time
dAVA 36 hours
M RF 84 hrs
Forecasts verifying Feb, 0
100
z500 anomaly correlation
80
dAVA
60
MRF
40
20
0 1224364860728496108
120
132
144
lead (hours)
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.
QJ 1958
INITIAL
30 jan
15Z
+24 hr
barotropic
forecasts
31 jan
15Z
(anl)
Analysis 31
Jan 15Z
1953,
500mb(ft)
24 hr forecast of
500mb height by
Sawyer_Bushby
Model, verifying
Jan 31 15Z, Met
Magazine
1954
+24 hr by
Sawyer_Bushby
model
“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
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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
31 Jan 3Z
01 Feb 3Z
0(28)
0(27)
0(22)
24
34
24
43
54
57
57
68
73
96
95
108
140
129
137 gpm
MSLP
Lead — >
30 Jan 3Z
31 Jan 3Z
01 Feb 3Z
0
24
48
72
96 hr
------------------------------------------------------------0(1.8)
3.2
5.2
7.4
9.6
0(2.0)
4.1
6.7
8.1
7.4
0(2.4)
2.9
6.3
6.7
9.8
climo
10.7
12.8
15.1 mbar