Typical Synoptic
Situation
Summer (from November to March)
The high pressure systems at this time of year often lie in the Great
Australian Bight and the Tasman Sea. Between these systems lies low pressures
that are often associated with cold fronts. The cold fronts rapidly move along
the New South Wales coastline. They are often known as the Southerly Busters and
they occur approximately every 5 days. The effect of the Southerly Busters on
the inland region of the Hunter Valley is minimal in comparison to the
coast.
Trough lines, which often extend southward from Queensland,
are a common occurrence over the Hunter region at this time of year. These low
pressure troughs often bring unstable weather, such as rain events and
thunderstorms.
Winter (from April to October)
The Hunter region at this time of year is often dominated
by the mid latitude westerlies. These winds are usually west to southwest in the
upper Hunter, but due to the topography of the Hunter Valley, these winds often
become northwestely by the time they reach the lower Hunter and the coast. The
terrain of the Hunter Valley creates a funnelling flow effect on the
winds.
Cold fronts pass through every so
often, commonly approaching the Hunter region from the southwest. These cold
fronts can bring showers to the inland areas and the ranges. They also bring
snow at times to higher grounds.
Rainfall
The rainfall is within 1000 – 1300 mm (40 - 62 in) per
annum on the coast. The rainfall from the coast drops the further you go inland.
Around Maitland/Cessnock (Lower Hunter) the rainfall is between 800 – 950 mm (32
- 38 in). Singleton (mid Hunter) and the surrounding areas receive around 700 mm
(28 in) and the areas around Scone (Upper Hunter) receive close to 650 mm (26
in). The highest rainfalls of the Hunter occur around the Barrington Tops. Some
of the elevated and southeastern parts of the tops receives 1500 mm (60 in) or
more. The driest region of the Hunter Valley is around the areas of Merriwa,
where the average yearly rainfall is as low as 580 mm (23 in). In general
rainfall decreases in the main valley the further away from the coast, but it
increases with the elevation.
Temperatures
The temperatures vary between the coast and the inland
areas all year. Generally in the winter the temperatures inland are cooler then
the coast, but due to the effect of the sea breezes on the coast, the
temperatures are warmer inland during the summer. Daytime averages during the
winter vary from around 14-15°C (57-59°F) around the Murrurundi area, to 15-16°C
(59-61°F) around Scone and 16-18°C (61-64°F) around the lower Hunter and the
coast. Average overnight temperatures during winter range from as low as 2°C
(36°F) in Murrurundi to milder 9°C (48°F) averages on the coast.
Summer daytime averages are around 30-32°C (86-90°F) in the
Upper Hunter, to around 28°C-30°C (82-86°F) in the Lower Hunter. Towards the
coast it is around 27°C (81°F). Temperatures of around 38°C (100°F) near the
coast are not very common, but in the upper Hunter it can reach 42°C (108°F) at
times during the warmer months (November to March). During heatwaves, it is
common for the inland to record 3-5 days of temperatures above 35°C (95°F).
Jerrys Plains, near Singleton, records the highest temperatures along with
Richmond in Sydney metropolitan between the coast and the ranges in New South
Wales. It has been known to reach 45°C (113°F) on rare occasions and it can have
up to five consecutive days at a time where the temperature reaches above 38°C
(100°F). It is typical on a hot summer day for the coast and the Lower Hunter to
receive a refreshing sea breeze by the afternoon or evening. Sometimes the sea
breeze can penetrate westwards and reach as far as Scone.
Temperatures around the Barrington Tops and other higher
mountain areas would be considerably cooler then anywhere else in the Hunter due
to the high elevations. Unfortunately, there is no climatic data to indicate
this, although it can be estimated that average daytime temperatures on the
Barrington Tops at about 1500m would be around 6°C (43°F) during winter and
around 20-23°C (68°F) during the summer.
Frost, Snow and
Thunderstorms
There is approximately 30 days of frost a year in the upper
Hunter. Places near the slopes and valleys receive around 40 to 45 frosts per
year. The number of days of frost reduces to around 15 to 20 days per year
towards the lower Hunter, while the coast receives 0 to 2 frosts per year on
average. At times the frost can become severe, especially in the upper Hunter
and on the ranges.
Snow mainly occurs about the Barrington Tops and some of
the higher mountain areas in the Upper Hunter. Snowfalls above 1200m (4000ft)
during the winter are not uncommon, however, due to the lack of reliable
climatic data, it cannot be certain how many days a year would it snow. Over the
years, I have worked out that it snows on average about 2 times a year to levels
as low as 1000m (3300ft). On very rare occasions snow has settled as low as 400m
(1300ft). The Liverpool ranges (approx. 800m/2600ft) around Murrurundi can
appear to be snow capped for a day or two at times, but this only occurs
approximately every two to three years.
There are approximately 30-40 thunderstorm days per year
for the Upper Hunter, while the coast has about 20-30 days per year. Most of the
thunderstorms occur during the storm season which is October to April. At times
these thunderstorms can be very severe. They can produce large hail, strong
winds, heavy rain and even tornados.
