Possible NT cyclone for Xmas Day

An intensifying tropical low just over 200km north of Darwin off the Top End coast is expected to develop into a tropical cyclone early on Christmas Day. If it forms, it will be named Grant. A Cyclone Watch is current for coastal areas from Dundee Beach to Nhulunbuy, including Darwin.

While models are uncertain about the intensity and movement of this system, heavy rain is predicted for the north coast of the NT due to its slow-moving nature and proximity to the coast. Over 400mm is possible over the next few days with flooding likely.

If this tropical low develops into a tropical cyclone, it will be the third in the Australian region so far this season. Earlier in the month, Cyclone Alenga (named by Mauritius) drifted into the Australian Region of Responsibility but dissipated well off the coast with no impact on the west coast. The second of the season was a very shortlived Cyclone Fina in the Coral Sea, several hundreds of kiometres off the QLD coast.While this system had no direct impact on the coast, it is going to have a major influence on coastal conditions in southern QLD over the Christmas weekend. Cyclonic swell will coincide with a King Tide to produce waves of 8-10 foot extending to parts of northern NSW aswell. This will be a very dangerous time for holiday-makers wanting to go swimming, surfing and rock fishing, and there is a threat of beach erosion and inundation of low-lying areas.

Severe weather is also expected for south-eastern Australia during the Christmas period with a major thunderstorm outbreak! A hot, humid airmass is combining with a deepening trough to trigger widespread thunderstorms in TAS, VIC, southern NSW and the ACT on Christmas Day (including Melbourne and Canberra), moving north through central and northern NSW (including Sydney) on Boxing Day. Damaging winds, flash flooding and large hail are all possible!

Severe storms strike Perth with record breaking December rain!

Severe thunderstorms struck much of WA's southwest last night leading to widespread local flooding. Perth was soaked by a massive 44mm, with 37.8mm falling in just 46 minutes- this was greater than a 1 in 100 year event and, the equivalent of 3 times the December monthly average rainfall in just 46 minutes! It was also Perth's wettest December daily rainfall total in 60 years!

Surrounding areas were also awash with heavy rainfall Mandurah 69mm (heaviest December rain on record), Serpentine 37mm, Rottnest Island 36, Perth Airport 35 and Swanbourne 30mm.

The worst affected region was the Great Southern district with a large number of towns recording their heaviest December rainfall on record including: Narrogin (84.4mm), Wishbone (81.6mm), Dumbleyung (71mm), Rushy Pool (70mm), Katanning (61.8mm) and many others.

Williams had the highest rainfall in this event with a massive 125.6mm- the highest rain total ever recorded anywhere in the South West Land Division in December! This resulted in widespread flooding leading to evacuations.

The low pressure system responsible for the heavy rain and severe thunderstorms is moving eastwards today so rain has already eased for the west coast. Since 9am this morning, another 20-40mm has already been recorded in parts of the Wheatbelt, Goldfields and Southeast Coastal districts. As the system reaches the SA border it is expected to weaken, bringing patchy light rain to that state.

Widespread cloud cover due to rain and storms will capped maximums today with temperatures as much 13 below average for this time of year. Newdegate and Narrogin reached just 16 and 17 degrees today, respectively.

Summer is typically very dry for Perth with the city averaging only 12.8mm during December. This year has been very unusual for Perth and much of south-western WA with the city already receiving 75.8mm- now just 5mm short of its wettest December on record! 2011 marks a huge turnaround in rainfall from December 2010 when Perth recorded only 3.4mm.

First cyclone of the season in Australian waters likely to fizzle

Infared Image from Japan Meteorological Agency satellite MTSAT via Bureau of Meteorology- TC Alenga is the bright green/red system in the top left corner.

We could see the first tropical cyclone of the 2011-12 season in Australian waters with TC Alenga entering the Australian region of responsibility some time today.

It's situated in the central Indian Ocean and moving east southeast at 13kmh. It's expected to weaken on Thursday and Friday, and then dissipate well off the west coast of Australia due to unfavourable sea surface temperatures and atmospheric conditions. At this stage, the only influence that this system might have on the Australian mainland is rain for parts of the west coast like the Gascoyne/Pilbara due to increased moisture from the outflow of the cyclone.

I'll keep you posted!

Cold start to summer for Sydney!

Sydneysiders should make the most of today and Tuesday as they are likely to be the warmest days in a while!

Today is already shaping up to be a pleasant sunny day with 26-30 degrees with Tuesday forecast to reach 27-31 degrees.

After a warm night on Tuesday, the beginning of Wednesday will be a balmy 28-31 degrees before showers turn up from the late morning or early afternoon. There is also the potential for thunderstorms which may be severe. The wet weather will provide some cooling but a southerly change due on Wednesday night will lead to a significant temperature drop on Thursday.

Consequently, the first day of summer will feel like more like winter for Sydney with showers and just 20-21 degrees! Cooler than average summer temperatures in the low twenties are forecast to linger for at least another week from Thursday.

This cold and wet change for Sydney is part of a larger system that will affect most of NSW on Wednesday/Thursday. Of particular concern is the rain that is expected to fall over flood affected parts of north-west NSW with up to 50mm possible. While this rain event won't be as severe as last week, it is likely to lead to secondary flood peaks on some rivers.

Sydney bakes in hottest day this spring!

It was a scorcher in Sydney today with temperatures as much as 14 above the November average! The city reached a scorching 37.2 degrees today- a massive 13 degrees above the November average maximum and its hottest day so far this spring!

Penrith was the hottest in Sydney's west with 38.7 degrees. Other notable mentions include Sydney Airport (37.9), Bankstown (37.3) and Campbelltown (37.4).

It's not often that Sydney city reaches the mid-30s in spring, but it's even rarer for the city to be as hot as the western suburbs. The main reason why the city and coastal suburbs usually experience cooler conditions than the west on a hot day is the seabreeze. But today hot NW winds were gusting to 50-60kmh which was strong enough to effectively cap the seabreeze for most of the day, allowing the mercury to rise well above the forecast maximum of 32 degrees, and November average maximum of 24 degrees.

Relief!

Fortunately, relief arrived with a southerly change this evening dropping temperatures by around 10 degrees in 20 minutes! Overnight temperatures should dip below 20 degrees, much more comfortable than the 26-27 degree night that sleepless Sydneysiders sweated through last Wednesday.

Rest of the week?

The rest of the working week will be more bearable with a sunny 26-31 degree day on Tuesday. Wednesday is forecast to reach 25-29 degrees with a stronger southerly change and showers and storms during the afternoon. This will lead to a cooler 23-24 degrees on Thursday with one or two showers. Friday will warm back up to 27-31 degrees with a possible morning shower. Hotter weather is expected next weekend though, with temperatures potentially reaching the mid-30s once again.

Temperatures were even hotter in the western NSW today with Bourke sweating through 41.5 degrees.

Showers making way for a warm weekend in Sydney!

After its driest October in 4 years with just 37.4mm, Sydney has kicked off November in typical erratic spring fashion- sunshine, a southerly buster and widespread showers! Yesterday the city and west enjoyed  a sunny day with 24-27 degrees before a southerly change delivered winds up to 40-50kmh. Late afternoon cloud increased across the city with showers developing overnight.

Moist south-easterly winds have delivered the heaviest falls to coastal suburbs, especially the northern beaches, with lighter falls further west. To 9am this morning: Avalon 25mm, Cronulla 17mm, Chatswood 14mm, City 11mm, Homebush 10mm and Penrith 3.6mm. The mercury will also struggle to get to 20 degrees today across most suburbs. But this gloomy weather will be short lived!

Showers are easing and becoming isolated on Thursday afternoon with dry and partly cloudy skies on Friday with 23-35 degrees. The weekend is heating up on both days with a muggy 27-31 degrees on Saturday with a hot 30-34 degrees on Sunday, around 6-7 degrees above average for November.

Early next week it's expected to stay warm although less comfortable with rising humidity and unstable conditions with the chance of showers and storms. A trough is expected to trigger showers and storms through inland parts of NSW on Sunday and there is a chance that some of these showers and storms may drift towards Sydney as early as Sunday afternoon/evening.

Unseasonal rain and storms in WA!

Record breaking rain hits inland WA...
October ended with record breaking rainfall for normally dry central and northern parts WA. In the past week areas of the Interior and Goldfields picked up 50-100mm of rainfall while parts of the Kimberley have seen over 100mm.

Wiluna in the northern Goldfields received 38mm to 9am Tuesday morning, its heaviest November day of rain in over 100 years of records! Nearby Packsaddle Farm saw 64.8mm on the same day, its heaviest November day of rain since records began in 1995. Both Giles and Warburton in the Interior picked up over 70mm for the month, most of it in the last week, which is almost 5 times their monthly October average rainfall!

Many inland parts of WA would typically receive no more than 20mm on average for the month of October so this heavy rain is unusual for this time of year.

WA Rainfall totals (mm) Week ending 1st November 2011. Source: Bureau of Meteorology

Perth and southern WA next...
While the heavy rain and storms have been concentrated in central and northern parts of the state over the last few days, it will start to ease from tomorrow with the focus shifting further south. Widespread rain and potentially severe storms are expected for southern parts of the state on Thursday.

Perth is a chance to see a storm on Wednesday afternoon but the greatest risk is on Thursday with severe storms possible in Perth with the potential of flash flooding.

On Friday the rain and storms will shift eastwards across the state providing a break for Perth, but lighter showers are still expected in the city for the rest of the week from frontal activity.