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A reconstruction of the August 1st 1674 thunderstorms over Holland

TL;DR: In this article, the velocity of the extremely severe 1674 squall line and its orientation, including a developed bow-echo structure, are reconstructed using modern meteorological concepts, and an estimate of the wind 5 speeds associated with this event and the return time of this event is given.
Abstract: On August 1st 1674 an active cold front moved over the low countries. The accompanying thunderstorms along the squall line were abnormally active, leading to large-scale damage in Europe, from northern France to the northern parts of Holland where damages were particularly severe. Using reported and pictured observations of damages, a reconstruction of this storm is made and an interpretation using modern meteorological concepts is given. The velocity of this exceptionally severe squall line and its orientation, including a developed bow-echo structure, are reconstructed. An estimate of the wind 5 speeds associated with this event and an estimate of the return time of this event is given. This storm is compared to a more recent storm which was similar in dynamics but much less devastating. Special attention is given to the city of Utrecht which was hit hardest, and where the impact of this storm is still recognisable in the cityscape.

Summary (4 min read)

1 Introduction

  • Wednesday 1 August 1674 (new/Gregorian calendar) ended in thunder and lightning over the Netherlands, which is not uncommon for a typical warm and humid Dutch summer day.
  • The passage of the front was noted as far east as Hamburg (northern Germany; see Fig. 1 for the location of mentioned places).
  • In addition to a description of a historic event, the reconstruction and analysis of this summer storm event illustrates the impact of a storm of this ferocity that is rare enough not to be captured by the modern weather radar archives (which are a few decades long) but apparently not unlikely to occur.
  • These thunderstorms were not only in Holland but also in other provinces.
  • Especially Utrecht city and surrounding villages were hit hard, where church towers from five surrounding villages were partly or completely destroyed based on newspaper accounts (Haerlemsche Courant, 1674).

2.1 Used sources

  • The general structure and a considerable amount of the wording in these articles are similar.
  • Drawings by the landscape painter Herman Saftleven (1609–1685) were commissioned by Utrecht city council to record the damage in and around the city in great detail.
  • A similar collection of sources for descriptions of the storm and its damage is provided by Graafhuis and Snoep (1974) and Graafhuis (1974).

2.2 Summary of contemporary descriptions of the storm and its damage

  • The short duration of the storm is made clear in Kooch’s account of the damage in Amsterdam.
  • One account from the city of Hilversum (Kooch, 1674, strophe 45 and 46) is indicative of the enormous damage which affected this town where 50 homes were levelled and others badly damaged, causing many deaths (van der Aa, 1839).
  • Inquiries with the historical societies of the cities Leiden and Delft, close to the North Sea coast but more south than Haarlem, show that no damage is known that is related to this storm (Historical Societies of Delft and Leiden, personal communication, 2016).

3.1 Reconstruction

  • The widespread damage in the east–west direction and the rapid passing of the storm point to a narrow frontal structure passing over the Low Countries.
  • These estimates can only be made consistent with each other by using speeds close to the lower bounds for the Antwerp–Amsterdam and Antwerp–Utrecht sections, and close to the upper bound for the Utrecht–Amsterdam section.
  • These diverging estimates of the average speed of the frontal system are consistent with a situation that an accelerating part of the squall line passed Utrecht while the western part of the squall line, travelling at lower speed passed through the area west of Amsterdam.
  • The rear-inflow jet advects high-momentum winds from aloft, further enhancing the wind speeds at the surface.
  • Still smaller areas of extreme wind within microbursts are called burst swaths, which range from 40 to 140 m (Fujita and Wakimoto, 1981).

3.2 Is there evidence of embedded vortices?

  • Apart from the bookend vortex of the squall line, the straightline wind associated with the bow echo may have embedded vortices which are produced by horizontal shear.
  • The bells of this tower fell through the church roof, destroying the arches.
  • The pattern of damage reflects the burst swaths associated with these downbursts where most trees fell in the direction of the movement of the front.

4 Estimate of the strength of the storm

  • There are no direct measurements of the strength of the mean winds and wind gusts at the surface generated by the downbursts of the storm.
  • In order to make an assessment of the strength of this storm and a provisional estimate of its return period, two approaches are tried.
  • One relates the observed damage to a wind strength via the Fujita scale (Fujita, 1958; Fujita and Wakimoto, 1981).
  • The other attempts to make a return period analysis using a modern climatology of hail and observed hail size.

4.1 Wind strength estimate

  • The accounts of the storm from the newspaper reports, the drawings of Saftleven, and especially Kooch’s rhyme are detailed to the point that a Fujita damage scale2 can be attached to the storm.
  • In Kooch’s rhyme are several accounts, mostly from the water-rich northern parts of Holland, of prams being taken up into the air to be transported (in one account) “over several fields”.
  • Of the seven windmills on the city wall of Utrecht, perhaps one survived the storm (Perks, 1974).
  • The F3 scale for “severe damage” describes “roofs and some walls torn off well-constructed houses”, “most trees in forest uprooted” and “heavy cars lifted off the ground and thrown”.
  • In the heavier-hit areas, like the city of Utrecht, such damage to roofs and walls is evident in the drawings of Saftleven.

4.2 Return period estimate

  • The severest damages caused by this storm are from the wind gusts and a return period estimate should be based on the strength of the wind gusts.
  • Gottfried (1700) notes that the weight of the hail stones observed near Paris were “three and a half pound”.
  • Nat. Hazards Earth Syst. Sci., 17, 157–170, 2017 makes the translation from these observations into modern metrics difficult.
  • The average daily maximum temperatures for southern Finland and the Netherlands are 20.1 and 21.9 ◦C respectively and the number of summer days (days where the daily maximum temperature is ≥ 25 ◦C) are 17.0 and 20.5 respectively, calculated over the 1981–2010 climatological period6.
  • Tuovinen et al. (2009) have collected accounts of severe hail (diameter of 2 cm or more) by newspaper report, storm spotters, and eyewitness reports.

5 Comparison against a recently observed bow echo

  • A modern – but much less devastating – equivalent to the summer storm of 1 August 1674 is the squall line with an embedded bow echo that occurred on 14 July 2010 and passed over Belgium, the westernmost part of Germany and the southeast of the Netherlands.
  • The most active part of this frontal system was part of a long squall line which extended into Switzerland and it caused severe wind damage in the Netherlands, particularly near the villages of Vethuizen, 85 km ESE of Utrecht, and Neerkant (60 km SSW of Vethuizen).
  • The storm caused two casualties in Vethuizen.
  • The Vethuizen storm is described in some detail in this section based on an earlier technical report (Groenland et al., 2010), in terms of damage and meteorological interpretation, and the similarities between the 1674 storm and this modern equivalent are pointed out.

5.1 Damage survey

  • The first report of strong wind gusts was at 15:32 UTC at Maastricht Aachen airport (southernmost part of the Netherlands) with 31 m s−1.
  • This showed a destroyed farm with its tiles removed from the roof, the chimney broken off and part of the facade of the farm destroyed.
  • Large damage occurred to five power pylons in this area which were blown down.
  • The direction of the fall of all these pylons was in the direction of the movement of the frontal system.
  • It was estimated that about 75 % of the trees in this area had been damaged, mostly oak with an approximate age of well over 50 years.

5.2 Synoptical analysis

  • European weather maps (Fig. 9) show a low-pressure area, of just below 990 hPa, south of Ireland, and in combination with a powerful ridge of high pressure, a southern flow over the Low Countries is generated.
  • The enhancement of thermal contrasts over western Europe fuelled the development a thermal low.
  • Less than 30 min later, the cyclone arrives in the Netherlands, passing in 6 h towards the eastern parts of the Netherlands.
  • The characteristic spatial scales at which such high values occur are too small for the density of the observing network to be measured.

5.3 Similarities and differences between the 1674 and the 2010 events

  • From the meteorological perspective, many similarities can be observed between the 1674 and the 2010 situation.
  • The direction of movement of the squall line, from SSW to NNE, is similar and matches the direction of movement of the strongest squall lines in the modern climatology of the Netherlands.
  • With the rapid approach of the frontal system, a dark band of clouds was observed (Groenland et al., 2010), similar to what was reported in 1674 by a source (Buisman, 2000) from the town of Medemblik (44 km NNE of Amsterdam).
  • The lack of sufficient detail in the observations prevents confirmation or reconstruction of these structures.

6 Discussion and conclusions

  • Estimates of the number of people severely injured or dead due to this storm are lacking.
  • The lack of estimate of the loss of life makes it seem that the impact of this storm was most profound in terms of material loss, but the human cost must have been extensive.
  • It has been argued that the nave of the Dom cathedral might have been more vulnerable because of the lack of flying buttresses and because of having a roof supported by a wooden structure rather than an overarching stone structure (den Tonkelaar, 1980).
  • The damage caused by the 1925 event can be traced from the southeastern part of the Netherlands in the NNE direction to the eastern parts of the Netherlands over an interrupted path several tens of kilometres wide.
  • It is interesting that the confusion on the cause of the damage (tornado vs. straight-line winds) is commented on by Fujita and Wakimoto (1981) who indicate that “this type of damage has often been reported as tornado damage” rather than as due to straight-line winds from a downdraft.

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Nat. Hazards Earth Syst. Sci., 17, 157–170, 2017
www.nat-hazards-earth-syst-sci.net/17/157/2017/
doi:10.5194/nhess-17-157-2017
© Author(s) 2017. CC Attribution 3.0 License.
A reconstruction of 1 August 1674 thunderstorms
over the Low Countries
Gerard van der Schrier and Rob Groenland
Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
Correspondence to: Gerard van der Schrier (schrier@knmi.nl)
Received: 9 August 2016 Discussion started: 7 September 2016
Revised: 14 December 2016 Accepted: 29 December 2016 Published: 10 February 2017
Abstract. On 1 August 1674 an active cold front moved
over the Low Countries. The accompanying thunderstorms
along the squall line were abnormally active, leading to large-
scale damage in Europe, from northern France to the north-
ern parts of Holland where damages were particularly severe.
Using reported and pictured observations of damages and
modern meteorological concepts, the reconstruction of the
storm points to an exceptionally severe squall line. The ori-
entation and the velocity of the squall line are reconstructed
and shows a developed bow-echo structure. An estimate of
the strength of the strongest wind gusts is 55–90 m s
1
and is based on an assessment of the damages caused by this
event. A rough estimate of the return time of this event, based
on observed hail size, is between 1000 and 10 000 years. This
storm is compared to a more recent storm which was similar
in dynamics but much less devastating. Special attention is
given to the city of Utrecht which was hit hardest, and where
the impact of this storm is still recognizable in the cityscape.
1 Introduction
Wednesday 1 August 1674 (new/Gregorian calendar) ended
in thunder and lightning over the Netherlands, which is not
uncommon for a typical warm and humid Dutch summer
day. Different from other days was that the meteorologi-
cal conditions of this day led to the formation of a line of
thunderstorms along the cold front which developed to ex-
tremely severe levels. During the passage of this line, wind
gusts caused severe damages over an area from northern
France, into (what was called in the 17th century) the Span-
ish Netherlands and the Dutch Republic. The passage of the
front was noted as far east as Hamburg (northern Germany;
see Fig. 1 for the location of mentioned places). The dam-
age was overwhelming in the Netherlands and this storm was
referred to at the time (in Dutch) as “het Schrickelik Tem-
peest”, or the Terrible Tempest.
Using modern insights in mesoscale meteorology and by
gathering impact-related evidence and accounts from various
sources, we take a fresh look at this day, analyse the event
and make an estimate of its severity in terms the strength of
the wind gusts and its return period. Here we argue that this
event is characterized by strong straight line winds resulting
from downbursts. This contrasts with the popular view that a
single tornado caused this damage. However, we argue in this
study that vortices, embedded within the frontal structure, are
likely to have been present. In addition to a description of a
historic event, the reconstruction and analysis of this summer
storm event illustrates the impact of a storm of this ferocity
that is rare enough not to be captured by the modern weather
radar archives (which are a few decades long) but apparently
not unlikely to occur. The quantification of the strength of
the wind gust associated with this event may provide a per-
spective on the disruption to society in case such a rare event
would occur again.
A summary of the storm event is given by the newspaper
“The Dutch Mercurius” of August 1674 (Hollandsche Mer-
curius, 1674):
On the first day of this month, in the evening
around 8 o’clock nearly throughout all of Holland
a terrible thunderstorm passes, mixed with Thun-
der and Lightning, Winds, rain and hail. Severe
damage in Amsterdam occurred, where the power-
ful winds overturned most of the trees, many ships
broke adrift from the quay of which nine sunk and
several houses lost their facades. Hardly any house
Published by Copernicus Publications on behalf of the European Geosciences Union.

158 G. van der Schrier and R. Groenland: 1674 summer storm over Holland
Figure 1. Cities, towns and villages mentioned in the text.
The numbers in the map refer to (1) Alkmaar, (2) Amsterdam,
(3) Antwerp, (4) Brussels, (5) Delft, (6) Fontainebleu, (7) Frankfurt
am Main, (8) Haarlem, (9) Hamburg, (10) Hilversum, (11) Ilpen-
dam, (12) Koog aan de Zaan, (13) Leiden, (14) Neerkant, (15) Stras-
bourg, (16) Texel, (17) Utrecht, (18) Vethuizen.
was found that had no damage to its tiles, win-
dows or something else. Several windmills were
overturned by the wind (. . . ) As it was all prayers
day, many men were outside, and many of them
were never seen again. Several other towns in Hol-
land suffered damage as well, though not as much
as Amsterdam. On the island of Texel, the furious
winds drove many ships on the beach or were sunk.
The largest damage happened in Utrecht because
in a quarter of an hour most of the houses lost their
facades and roofs. (. . . ) These thunderstorms were
not only in Holland but also in other provinces. In
Brussels, hail stones fell which were as large as
marbles, many trees were removed from the Earth,
but also many house facades were overthrown. The
bridge in Antwerp, which lay over the river Scheld,
was destroyed by the strong winds, and the ships
drifted away on the river. In Hamburg and in the
area of the river Elbe this thunderstorm was felt
as well. In Strasbourg, hailstones fell as large as a
baby’s head.
Figure 2. Drawing of the ruin of the Dom cathedral following the
1674 storm by Herman Saftleven (Utrecht City Archive no. 28635).
The viewpoint of the artist is from the undamaged part of the Cathe-
dral overlooking the area with the collapsed nave towards the Dom
tower.
The storm caused an enormous amount of damage in the
Dutch provinces of Holland and Utrecht (located in the west
and central parts of the Netherlands). Especially Utrecht city
and surrounding villages were hit hard, where church towers
from five surrounding villages were partly or completely de-
stroyed based on newspaper accounts (Haerlemsche Courant,
1674).
The Dom cathedral in Utrecht probably suffered most
from the storm. Although the church had seen storm damage
from earlier storms, this time the nave of the church, between
the tower and the transept, collapsed (Fig. 2).
2 Accounts and descriptions of the storm
2.1 Used sources
There are several newspapers and a pamphlet which provide
descriptions of this storm and its damage (Sweerts, 1674;
Haerlemsche Courant, 1674; Hollandsche Mercurius, 1674;
Nat. Hazards Earth Syst. Sci., 17, 157–170, 2017 www.nat-hazards-earth-syst-sci.net/17/157/2017/

G. van der Schrier and R. Groenland: 1674 summer storm over Holland 159
Amsterdamse Courant, 1674). Although details in these ac-
counts differ, the general structure and a considerable amount
of the wording in these articles are similar. This indicates that
the three newspapers and the pamphlet should be regarded as
one source rather than four independent sources.
The exact circumstances during and after the storm
are well known due to the publication of Gerrit Jansz.
Kooch (1674), skipper and merchant (1597/98–1683). Kooch
(1674) painted a picture of the damage in the Netherlands
in a poem of 138 couplets. He also collected some informa-
tion about the damage in (what is now called) Flanders (Bel-
gium). Its sources include official publications on the storm
(likely including the newspaper articles mentioned above),
but he also wrote to people and used his network of friends
and family to gather damage reports. Furthermore, he asked
carpenters and roofers about the extent of the damage and he
investigated himself the extent of the damage by interview-
ing people who he then introduced in his poem. The rhyme
begins with Kooch’s personal account of the impact of the
storm on his surroundings in Amsterdam and then gives de-
scriptions of damages from Flanders, following the path of
the storm northward until it leaves Holland over the North
Sea. Some additional information on Kooch is provided by
Pfeifer (2015).
Drawings by the landscape painter Her-
man Saftleven (1609–1685) were commissioned by
Utrecht city council to record the damage in and around the
city in great detail. The sheer amount of drawings depicting
the damage of the storm in the vicinity of Utrecht (over 25
are available in the Utrecht city archives
1
while some
60 drawings are known to exist; A. F. E. Kipp, personal
communication, 2016) indicate the widespread character of
the damage this storm produced. An inventory of Saftleven’s
known drawings of the ruins in and around the city is
provided by Kipp (1974) and reproduced by Graafhuis and
Snoep (1974). Some of these drawings depict damage within
the city walls (18 focusing on the Dom Cathedral, five of
other subjects) but most (45 in total) depict damage in the
vicinity of the city, outside the walls.
In the summaries of local histories of all Dutch cities and
villages compiled by van der Aa (1839), damage due to the
events surrounding the 1674 storm is frequently mentioned.
In a historical description of events by
Joh. Lodew. Gottfrieds (Gottfried, 1700), published
in 1700, the storm of 1674 and the damage it caused is
described to some detail.
Finally, Buisman (2000), in his impressively detailed de-
scription of each single season in 1000 years of weather in
the Low Countries, collected a vast amount of descriptions
of this storm from city archives, official records and diaries.
A similar collection of sources for descriptions of the storm
and its damage is provided by Graafhuis and Snoep (1974)
and Graafhuis (1974).
1
http://www.hetutrechtsarchief.nl/
2.2 Summary of contemporary descriptions of the
storm and its damage
The short duration of the storm is made clear in Kooch’s ac-
count of the damage in Amsterdam. His personal experience
was that the storm passed in a short half hour (strophe 10).
Later, one of his sources claims that the storm passed over
Amsterdam in a quarter of an hour (strophe 80 and 81) and
that no house would have been undamaged if the storm were
to have lasted a full hour. Sweerts (1674) writes that in less
than half an hour the whole town of Utrecht was turned to
ruins.
The passing of this system saw unusually strong gusts
which are described in Kooch’s report, accounting numerous
cases of people, small boats and carriages taken up into the
air. The impact of the storm on the landscape is also made
clear by Kooch (1674, strophe 42–44) in which a farmer fails
to recognize the surroundings of his grass land after the pas-
sage of the storm, with not only the haystacks blown away,
but the trees along the borders of his land and church towers
of a nearby town as well.
The destructive force of the gusts was illustrated by the
nature of the damage: churches collapsed, church choirs and
spires were damaged or destroyed, wind mills were over-
turned, pieces of lead used as roofing (some of them 150
pounds in weight) were blown off completely and roofs
of houses were ripped off. One account from the city of
Hilversum (Kooch, 1674, strophe 45 and 46) is indicative
of the enormous damage which affected this town where
50 homes were levelled and others badly damaged, causing
many deaths (van der Aa, 1839).
There are several reports from the water-rich province of
North Holland about boats that did not survive the storm. An
example from the area near Ilpendam (north of Amsterdam),
was of two farmers who were first blown out of the boat and
then the boat was taken up by the winds, flying “over several
fields”. The boat was shattered to pieces when the farmers
found it again (Kooch, 1674, strophe 119 and 120).
The amount of rain (Kooch, 1674, strophe 91–95) must
have been exceptional. It was described as “the rain was over-
whelming”, “as if buckets were emptied”, “it came streaming
down the streets”, and “the rain, which came like the Deluge,
flooded the houses, ruined the walls and spoiled the grain that
was left on the fields”. Kooch also reports on the remark-
able size of the hail stones. Other reports of large hail stones
come from northern France, Belgium and the Netherlands
(Hollandsche Mercurius, 1674; Buisman, 2000).
A compilation of all damage reports is shown in Fig. 3.
Multiple reports for one city or village are shown as one re-
port. The figure clearly shows the path, from North France
over Flanders into the western part of the Netherlands. Got-
tfried (1700) notes that the storm was violent in North
France, with the hail and winds causing severe damage
to grain fields, grapes and orchards. The Royal Palace of
Fontainebleau was “severely damaged” as well. The figure
www.nat-hazards-earth-syst-sci.net/17/157/2017/ Nat. Hazards Earth Syst. Sci., 17, 157–170, 2017

160 G. van der Schrier and R. Groenland: 1674 summer storm over Holland
Figure 3. Damage reports compiled from various sources related to
the 4 August 1674 storm.
shows hardly any damage in the eastern parts of the Nether-
lands. Although these parts were relatively sparsely popu-
lated, no damage reports for some larger cities have been
found which were related to this storm.
It is interesting that in the westernmost parts of North and
South Holland almost no damage was seen (Fig. 3). This re-
markable feature is also noted by Kooch (1674, strophe 114),
mentioning Alkmaar and Haarlem. Inquiries with the histori-
cal societies of the cities Leiden and Delft, close to the North
Sea coast but more south than Haarlem, show that no damage
is known that is related to this storm (Historical Societies of
Delft and Leiden, personal communication, 2016).
At smaller spatial scales, the contrasts in damage are also
striking. Kooch (1674, strophe 110) notes that in Amster-
dam harbour the ships broke from their moorings and drifted
away, while empty barrels on the quay were unaffected. What
is striking about the drawings of Saftleven (Fig. 4) is that the
houses around the cathedral square, visible in the background
of the drawing, still appear to be intact. Even the facades are
intact and the pinnacles on the facades appear undamaged.
A tree apparently survived the storm. Kooch notes some of
these contrasts (strophe 77) when describing how a poorly
maintained little house, weakened to the point that it could
be brought down “with bare hands” was undamaged by the
storm.
The thunderstorms produced a long track of massive de-
struction through the province of North-Holland, without los-
ing strength. Damage was reported as far as the northern part
of Holland at Texel Island.
3 Meteorological interpretation
3.1 Reconstruction
The widespread damage in the east–west direction and the
rapid passing of the storm point to a narrow frontal structure
passing over the Low Countries. Such cold fronts are com-
mon in the summer season, replacing warm humid air with
cooler air.
A few sources match the passage of the front to the time
of day. Between 18:00 and 19:00 LT (local time) the storm
passed Antwerp (Kooch, 1674, strophe 12) to arrive between
19:00 and 19:30 LT at Utrecht (Sweerts, 1674) and just be-
fore 20:00 LT (Kooch, 1674, strophe 80) or around 20:00 LT
the front passed Amsterdam (Hollandsche Mercurius, 1674).
The front passed Koog aan de Zaan between 20:00 and
21:00 LT (Buisman, 2000), which is northwest of Amster-
dam. The direction in which the front moved is estimated to
be parallel to the line on the west side of the damage reports
over the province Holland (north of 52
N). Note that even
in the small Dutch Republic there were different time zones;
these timings are adjusted. When using the distances between
the centres of Antwerp, Utrecht, and Amsterdam, and the un-
certainties in the timing of the passage of the front, lower and
upper bounds of the average speed can be calculated between
these cities. For Antwerp–Utrecht and Antwerp–Amsterdam,
the lower bounds are 70 and 60 km h
1
respectively (up-
per bounds are unrealistic at > 150 km h
1
). For Utrecht–
Amsterdam, the upper bound is 78 km h
1
(lower bound is
unrealistic at 26 km h
1
).
Decomposing these estimates into the direction parallel to
the movement of the squall line and one perpendicular to
it, the average speed of the frontal system on the west side
of the front (passing through Antwerp) is about 60 km h
1
.
More to the east, passing trough Utrecht, the speed is about
65 km h
1
. These estimates can only be made consistent
with each other by using speeds close to the lower bounds
for the Antwerp–Amsterdam and Antwerp–Utrecht sections,
and close to the upper bound for the Utrecht–Amsterdam sec-
tion. These diverging estimates of the average speed of the
frontal system are consistent with a situation that an accel-
erating part of the squall line passed Utrecht while the west-
ern part of the squall line, travelling at lower speed passed
through the area west of Amsterdam.
The distance between Amsterdam and Koog a/d Zaan is
too small ( 4 km) and the timing estimates have too large
uncertainties to be of much use.
An accelerating central part of the squall line and an area
west of the squall line without significant damage point to
Nat. Hazards Earth Syst. Sci., 17, 157–170, 2017 www.nat-hazards-earth-syst-sci.net/17/157/2017/

G. van der Schrier and R. Groenland: 1674 summer storm over Holland 161
Figure 4. Drawing of the ruin of the Dom cathedral following the 1674 storm by Herman Saftleven (Utrecht City Archive no. 28637 and
no. 28630, both views from the southeast).
the existence of a bow echo. A bow echo is formed when
the band of convective thunderstorms is combined with a
rear-inflow jet. When this rain-cooled downdraft of a thun-
derstorm reaches the Earth’s surface, it spreads horizontally
and most rapidly in the direction in which the front pro-
gresses, producing straight-line winds. The rear-inflow jet
advects high-momentum winds from aloft, further enhanc-
ing the wind speeds at the surface. Within these areas of con-
vective downdraft, or downbursts, smaller pockets of intense
winds exist which are referred to as microbursts. Microbursts
are characterized by spatial scales of approximately 4 km.
Still smaller areas of extreme wind within microbursts are
called burst swaths, which range from 40 to 140 m (Fujita and
Wakimoto, 1981). The strong heterogeneity at small spatial
scales of the storm damages are in line with this concept.
When the rear inflow jet bends the frontal system, bookend
vortices develop on either side of the jet which are advected
along with the front. The cyclonic vortex in the west will be
strong due to the interaction with the Coriolis force, making
the winds on the west side of the vortex much weaker, ex-
plaining the absence of damage in towns like Haarlem and
Alkmaar (which are to the west-northwest of Amsterdam
close to the North Sea coastline). The stronger winds due
to the bookend vortex at the west end of the squall line could
have contributed to the vast damages in Holland. The book-
end vortex at the eastern end lacks the interaction with the
Coriolis force and is much weaker, making the distinction be-
tween areas with or without damage further inland less clear
than at the west side of the bow echo.
3.2 Is there evidence of embedded vortices?
Apart from the bookend vortex of the squall line, the straight-
line wind associated with the bow echo may have embedded
vortices which are produced by horizontal shear. There are
no observations of a whirlwind in the accounts of Kooch (or
elsewhere). However, the direction in which church spires
fell in the city of Utrecht may indicate embedded vortices.
While the nave of the Dom cathedral and the towers of the
Nicolaaskerk fell in a northerly direction (in the same direc-
tion as the movement of the front), the drawings of Saftleven
show that the two towers of the Pieterskerk (200 m to the
ENE) were blown down in the direction of the nave and
choir of the church (Fig. 5, left panel). One account (Haer-
lemsche Courant, 1674) confirms that the church spires fell
through the roof of the Pieterskerk. The nave and choir of the
Pieterskerk faced east, indicating that the winds were perpen-
dicular to the direction in which the squall line moved and to
the direction of the straight-line winds.
The Jacobikerk, about 680 m northwest of the Dom cathe-
dral, had a spire of nearly 80 m height in 1674. Gottfried
(1700) writes that the spire fell between the church and the
surrounding houses without damaging any of these houses.
The most likely place for the spire to fall is then west or
even southwest of the Jacobikerk where a large square was
present. Adjoining the spire of the Jacobikerk, at the east
side, was a (much) smaller tower containing the carillon. The
bells of this tower fell through the church roof, destroying the
arches. The position of the bells after the collapse of the spire
has been documented (Kipp, 1974) and the damaged arches
have never been repaired. A view of the direction in which
the spire of the Jacobikerk fell is given in the right panel of
Fig. 5. This indicates a southwesterly fall direction. The dam-
www.nat-hazards-earth-syst-sci.net/17/157/2017/ Nat. Hazards Earth Syst. Sci., 17, 157–170, 2017

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Journal ArticleDOI
TL;DR: In this paper, a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, were proposed to cover a wide range of horizontal dimensions of airflow.
Abstract: In order to cover a wide range of horizontal dimensions of airflow, the paper proposes a series of five scales, maso, meso, miso (to be read as my-so), moso and muso arranged in the order of the vowels, A, E, I, O, U. The dimensions decrease by two orders of magnitude per scale, beginning with the planet's equator length chosen to be the maximum dimension of masoscale for each planet. Mesoscale highs and lows were described on the basis of mesoanalyses, while sub-mesoscale disturbances were depicted by cataloging over 20,000 photographs of wind effects taken from low-flying aircraft during the past 15 years. Various motion thus classified into these scales led to a conclusion that extreme winds induced by thunderstorms are associated with misoscale and mososcale airflow spawned by the parent, mesoscale disturbances.

668 citations


Additional excerpts

  • ...One relates the observed damage to a wind strength via the Fujita scale (Fujita, 1958, 1981)....

    [...]

01 Jan 1970

158 citations


"A reconstruction of the August 1st ..." refers background in this paper

  • ...The Netherlands has no climatology of hail, so the accounts of the size of hail stones cannot be compared to modern measurements. A climatology of severe hail, covering the period 1930-2006 is available in Finland (Tuovinen et al., 2009). Tuovinen et al. (2009) have collected accounts of severe hail (diameter of 2 cm or more) by newspaper report, storm spotters and eyewitness reports....

    [...]

  • ...The nave and choir of the Pieterskerk are facing east, indicating that the winds were perpendicular to the direction in which the squall line moved and to the direction of the straight line winds. The Jacobikerk, about 680 m northwest of the Dom cathedral, had a spire reaching up to nearly 80 m height in 1674. Gottfried (1700) writes that the spire fell down between the church and the surrounding houses without damaging any of these houses....

    [...]

  • ...The size (∼diameter) is a more useful, although Knight and Knight (2005) comment on the issues of quantifying hail size by a diameter (given that severe hail is usually not very symmetric)....

    [...]

  • ...The analysis of Wurman and Alexander (2005) suggests that damages scaled between the F2 and F3 scale relates to 5 second wind gusts of approx....

    [...]

  • ...There are anecdotes mentioning people getting injured, like hail stones bruising people caught in the fields (Kooch, 1674, strophe 72), or people getting hit by falling trees or other debris. Gottfried (1700) mentiones the death of more than 1000 people blown in the water and drowned within a 30 distance of less than ‘half a mile’ from Amsterdam....

    [...]

Journal ArticleDOI
TL;DR: A Doppler On Wheels (DOW) mobile radar followed this tornado and observed the tornado at ranges between 1.7 and 8.0 km during various stages of the tornado's life as discussed by the authors.
Abstract: A violent supercell tornado passed through the town of Spencer, South Dakota, on the evening of 30 May 1998 producing large gradients in damage severity. The tornado was rated at F4 intensity by damage survey teams. A Doppler On Wheels (DOW) mobile radar followed this tornado and observed the tornado at ranges between 1.7 and 8.0 km during various stages of the tornado's life. The DOW was deployed less than 4.0 km from the town of Spencer between 0134 and 0145 UTC, and during this time period, the tornado passed through Spencer, and peak Doppler velocity measurements exceeded 100 m s−1. Data gathered from the DOW during this time period contained high spatial resolution sample volumes of approximately 34 m × 34 m × 37 m along with frequent volume updates every 45–50 s. The high-resolution Doppler velocity data gathered from low-level elevation scans, when sample volumes are between 20 and 40 m AGL, are compared to extensive ground and aerial damage surveys performed by the National Weather Servic...

152 citations


Additional excerpts

  • ...The analysis of Wurman and Alexander (2005) suggests that damages scaled between the F2 and F3 scale relates to 5 second wind gusts of approx....

    [...]

Journal ArticleDOI
TL;DR: A climatology of severe hailstones (2 cm in diameter or larger) in Finland was constructed by collecting newspaper, storm-spotter, and eyewitness reports as discussed by the authors.
Abstract: A climatology of severe hail (2 cm in diameter or larger) in Finland was constructed by collecting newspaper, storm-spotter, and eyewitness reports. The climatology covered the warm season (1 May–14 September) during the 77-yr period of 1930–2006. Altogether, 240 severe-hail cases were found. The maximum reported severe-hail size was mainly 4 cm in diameter or less (65% of the cases), with the number of cases decreasing as hail size increased. In a few extreme cases, 7–8-cm (baseball sized) hailstones have been reported in Finland. Most of the severe-hail cases (84%) occurred from late June through early August, with July being the peak month (almost 66% of the cases). Most severe hail fell during the afternoon and early evening hours 1400–2000 local time (LT). Larger hailstones (4 cm or larger) tended to occur a little later (1600–2000 LT) than smaller (2–3.9 cm) hailstones (1400–1800 LT). Most severe-hail cases occurred in southern and western Finland, generally decreasing to the north, with th...

83 citations

Frequently Asked Questions (1)
Q1. What have the authors contributed in "A reconstruction of 1 august 1674 thunderstorms over the low countries" ?

In this paper, an analysis of the effects of a large scale storm on the Dutch coast is presented.