The springtime Tasmanian winds are wild and sometimes destructive, but why are they a common feature?

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Tasmanians and the cold go together like a roaring fire and a good book.

Down jackets, UGG boots, and thermal clothing are all common winter wardrobe items, and many snowmen have taken a trip to Kunanyi / Mount Wellington on a car windshield.

Roofs, trees and power lines were blown down when strong winds blew Hobart in early spring.(

ABC News: Bailey Kenzie

)

However, our cold tolerance is limited and on August 31, with the winter supposed to be over, we start dreaming of days at the beach and showing off our pale legs in shorts.

But spring has other plans. Keep your winter woolens outside and prepare your kites, as spring is the windiest season in Tasmania.

Let’s examine why this is the case by presenting and dissecting some of the major players in Tasmania’s weather and climate variability and explain their movements in spring.

Two cars crushed by a large gum tree overturned by strong winds
Trees can represent a dangerous danger during strong spring winds.(

ABC News: Edith Bevin

)

We will discuss cold fronts, anticyclones, the subtropical ridge, the 1940s, the southern ring mode and sea breezes.

Cold fronts are a common feature of Tasmania’s climate and are usually associated with unstable (convective) weather – they bring strong southwest winds, cooler temperatures, and precipitation.

Cold fronts are a key player in spring and can bring damaging or destructive winds and precipitation (or hail with colder systems).

The table below shows the wind gust data recorded overnight through September 7.

Site

Maximum wind gust speed

kunanyi / mount Wellington

148 km / h

Maatsuyker Island

139 km / h

Scotts Woodpecker

120 km / h

Mount Hartz

119 km / h

Cap Bruny

117 km / h

Hobart

109 km / h

The ability of cold fronts to pass through Tasmania depends on the location of high pressure systems – another very common weather factor in Australia (and Tasmania).

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High pressure systems are generally associated with more stable weather conditions and have the ability to prevent cold fronts from crossing the state.

A higher pressure band known as the Subtropical Ridge sits above Australia year round.

During the cooler months, usually May through October, the subtropical ridge stretches across the Australian mainland, leaving Tasmania exposed to many cold fronts that cross the state from the southwest.

Giant surf off Burnie's wharf catches the wind
A giant surf off the Burnie Wharf catches the wind.(

ABC Northern Tasmania: Rick Eaves

)

During the warmer months, usually November through April, the subtropical ridge generally migrates south and prevents most cold fronts from disturbing Tasmanians during our beach time.

However, there is still one passing which sometimes results in snow on kunanyi / mt Wellington and other elevated areas in December.

Snow covers the ground and the trees
It was early summer, but snow covered the ground at the Great Lake Hotel in Miena last December.(

Provided: John Warden

)

So we discussed high pressure systems and cold fronts, but what contributes to the windy weather in the spring?

Most Tasmanians have heard the phrase Roaring 40s, referring to a strong band of winds from the west, called westerly winds, which howl around the Earth between latitudes of 40 to 50 degrees.

An aerial view of a house with the roof removed
Roofs, trampolines, small pets are all sensitive when the winds are blowing.(

Submitted: Rohan Puri

)

For reference, Tasmania is between 40 and 44 degrees latitude.

Due to the lack of land (read: windbreaks) west of Tasmania, we usually carry the weight of these Roaring 40s; especially when there are no high pressure systems to protect us from their fury.

The Southern Ring Mode (SAM) is an index that measures the belt of westerly winds that surrounds Antarctica (the Roaring 40s are one of these winds).

When the SAM index is positive, the winds contract to move closer to the Antarctic continent and therefore do not push as strongly over Tasmania.

However, when SAM is negative, the westerly winds push further north and bring stronger winds over Tasmania.

So if we combine a negative SAM event with our usual springtime, we can be in a pretty windy time!

Finally, the warmer months are associated with sea breezes, which can reach 30-40 km / h.

Sea breezes usually occur when there is a lack of driving winds (i.e. we are under a high pressure system), and the temperature of the earth is much warmer than the temperature of the sea.

The wind will blow from the cooler sea surface towards warmer land temperatures, usually in the early afternoon, and last until the evening when the land begins to cool.

So if we encounter a warm spring day and there is no wind from larger systems, there may still be wind due to the sea breeze.

Yacht beached at Dodge's Ferry.
It is not uncommon for yachts to break moorings when strong winds rock the state.(

Facebook: MAST

)

In conclusion, spring experiences windy weather for many reasons.

It is important to consider the location of the subtropical ridge, cold fronts, Roaring 40s, SAM index and even sea breezes.

So remember, just because winter is “officially” over doesn’t mean the weather gods will play along. Always be prepared.


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