How HOT the Perth can be?(ZT)

钟声 · 发表于 2007-1-28 09:51:41

ERTH'S SUMMER</h1></center> <center><img src="http://members.iinet.net.au/%7Ejacob/sn.gif" /></center> <img src="http://members.iinet.net.au/cgi-bin/nph-count?link=/jacob/summer.html&width=5&show=no" />

 
Summers in Perth are generally hot and dry, the major weather
influences during summer in Perth is the sea breeze and the development
of a low pressure trough down the west coast.

A typical summer situation is when a large high in the Great
Australian Bight forms, which directs hot and gusty easterly winds from
inland Australia to Perth, and a trough starts to develop down the west
coast, temperatures are usually in the 30's and only a late weak sea
breeze may arise.

During the next 24 hours the trough of low pressure down the west
coast starts to deepen, winds become more to the north-east and the
mornings are hot, with usually an earlier sea breeze bringing some
relief.

The position of the trough is usually the deciding factor in how hot
it gets and what time the sea breeze reaches the city. It can mean the
difference of a 40 C day or a much cooler day of 25 C to 30 C.

However, the trough can also be responsible in giving much needed
rain to Perth. Sometimes it can become active and produce thunderstorms
particularly to the north and east of Perth, and on rare occasions
bring storms to Perth it self.

Some of Perth's hottest days on record occurred back in 1991. The
heat on this occasion began on the 29th January, 1991, and the maximum
temperature reached 40.1 C, the next day was the first day of school
for the new year, and students had to cope in extreme heat when the top
hit 43.2 C. Weather forecasters expected that the trough would move
inland sometime during the next 24 hours, and predicted at maximum of
39 C for the next day, however it got much hotter. That day was the
31st January, 1991, Perth sizzled overnight with a minimum of 25.5 C
recorded at 5.55am, then the temperature began to climb, by 9am it was
already 38 C, at 11am it was 42 C, at 1pm it was 44 C, and the new all
time record was 45.8 C at 1.50pm, the sea breeze then came in and gave
some small relief.

The 45.8 C record defeated the old record of 44.7 C which occurred
on the 12th January, 1978, however only a few weeks later record heat
was back.

It was the 23rd February, 1991, a large high pressure system was
situated in the eastern half of the Great Australian Bight, and
Tropical Cyclone Daphne was situated to the north of the state, between
the two, very hot and strong north-easterly winds were present. Perth's
minimum temperature was 25.2 C at 1am, at 7am it was 28.1 C, by 9am it
was 35.3 C, at midday it was already 43.2 C and then the all time new
record was established at 1.50pm with a top of 46.2 C, which beat the
old record of 45.8 C some few weeks earlier.

February, 1996 will be remembered as another hot period by Perth
residents, when the heat wave record of 16 days in a row of
temperatures over 32 C was established, with a number of days during
that period getting over the 38 C mark.

Even though Perth is known as a dry city during the summer, it can
still have extreme rainfalls on a particular day if a thunderstorm or
an ex-tropical cyclone hits the city.

Some notable days was the 54.6 mm on the 21st January, 1982, the
50.5 mm on the 16th February, 1955, the 87.1 mm on the 17th February,
1955, the 64.8 mm on the 22nd February, 1986 and the all time Perth
record occurred in summer when 120.6 mm was dumped on the city on the
8th February, 1992. However extreme rainfall such as these during Perth
summers are very rare.

Averages and extremes in Perth for the summer months:

 
<pre> DEC JAN FEB Av.MAX 27.4 30.0 30.5 Av.MIN 16.5 18.3 18.7 Hi.MAX 42.3 45.8 46.2 Hi.MIN 27.1 27.8 29.3 Lo.MAX 14.9 19.6 19.0 Lo.MIN 8.6 9.2 8.7 Av.RAIN 14.0 8.0 12.0 </pre>