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Thursday, February 19, 2015

Extreme Weather: Severe Tropical Cyclones Lam and Marcia make Australian landfall

Double Trouble: Two severe tropical cyclones are converging on the Australian coast. Tropical Cyclone Marcia developed in the Coral Sea off the Queensland Coast. Tropical Cyclone Lam developed in the warm waters of the Gulf of Carpentaria before moving north and west into the Arafura Sea.

This map from bureau of Meteorology shows Tropical Cyclone Lam hitting the Northern Territory and Tropical Cyclone Marcia about to make landfall between Mackay and Yeppoon on the Queensland coast.

Severe Tropical cyclone Marcia is the 4th recorded category 5 storm to make landfall on the Queensland coast. Previous category 5 storms included Cyclone Yasi in 2011, Cyclone Innisfail in 1918 and Cycline Mahina in 1899. See a list of Australia's worst tropical cyclones at Australian Geographic.

Follow the live reporting at the Brisbane Times or live reporting at the Guardian.

In the South Pacific the intensity of tropical cyclones is measured using the Australian tropical cyclone intensity scale, which is slightly different to the Saffir–Simpson hurricane wind scale used for North Atlantic hurricanes, here are the likely impacts of category 4 and category 5 storms under the Australian intensity classification system:

Category 3: Some roof and structural damage. Some caravans destroyed. Power failures likely. A Category 3 cyclone's strongest winds are very destructive winds with typical gusts over open flat land of 165 to 224 km/hr.

Category 4: Significant roofing loss and structural damage. Many caravans destroyed and blown away. Dangerous airborne debris. Widespread power failures. A Category 4 cyclone's strongest winds are very destructive winds with typical gusts over open flat land of 225- 279 km/h.

Category 5: Extremely dangerous with widespread destruction. A Category 5 cyclone's strongest winds are very destructive winds with typical gusts over open flat land of more than 280 km/h

This composite video from satellite images compiled by shows the rapid development over time of both cyclone systems.

TC Lam hits Northern Territory

TC Lam is was upgraded to Category 4 intensity on Thursday evening, with winds with gusts greater than 230 kilometres per hour. The warning zone is Goulburn Island to Numbulwar, including Nhulunbuy, Groote Eylandt and adjacent inland areas to Bulman.

The cyclone is expected to make landfall between Milingimbi and Gapuwiyak overnight on Thursday and early Friday morning, and then expected to weaken as it moves inland over Arnhem Land.

The remote community on Elco Island has been sheltering in a large workshop shed since Thursday morning. The eye of the cyclone passed over Elco Island about 9pm Thursday with power lost, and wind gusts at 205kph. Several hundred people in the community of Galiwinku on Elcho Island are experiencing the brunt of Cyclone Lam as the storm moves towards the Northern Territory mainland.

Earlier on Thursday, hundreds of people from the Aboriginal community of Warruwi were evacuated to Darwin on helicopters and planes.

Power is now out in Galiwinku, Gapiwiyak, Millingimbi. The Maningrida shelter is open.

Update 11:00am Friday 20/2 CST. Cyclone downgraded to category 2 with wind gusts of 155kph, 90 kms NNE of Bulman according to ABC News 24 (@ABCNews24)

An AFP report indicated that substantial damage had been caused to buildings and downed power lines and roads made impassable by debris and flooding. "Initial indications are that there has been substantial damage, initial reports are the airstrip is still intact but covered with debris," regional police commander Bruce Porter said of the Elcho Island community. "There are downed power lines. There are a number of trees down and many roads are impassable and we do have a number of buildings and houses that have been severely damaged."

Porter advised that reports from other isolated communities suggested structural damage in Milingimbi and Ramingining but Gapuwiyak appeared to have escaped with limited damage. There are no reports of major injuries.

Storm surge for tropical cyclone Lam was estimated to be about 0.4 metres at Nhulunbuyby according to the European based Global Disaster Alert Co-ordination System (GDACS). But the animation of storm surge shows an impact through all of the shallow waters of the Gulf of Carpentaria up to West Papua. An interesting ripple effect over a wide area affecting a long stretch of coastline.

GDACS assessed this storm as having a low vulnerability impact as the population affected by cyclone-strength winds (>120km/h) was estimated at about one thousand. The storm was classified under Saffir-Simpson as Category 1, with Maximum sustained wind speed: 148 km/h. The calculations by GDAC were based on advisory number 7 of tropical cyclone LAM-15 issued at 19 Feb 2015 18:00:00 (GDACS Event ID 1000144)

GDACS issued a red alert for floods and flash floods. Rainfall was estimated to reach values between 800 and 850 mm, with high likelihood for floods and flash floods with torrential rain reaching values between 33 and 41 mm/h.

TC Marcia landfall north of Yeppoon

TC Marcia is likely to make landfall as a category 5 intensity storm with a very destructive core with gusts to 295 km/h. During Thursday the severe tropical cyclone developed in intensity very quickly going from a category two storm at 11:00am to a category four at 6:00pm. The Bureau of Meteorology is predicting the storm to intensify to a Category 5 storm before landfall. Landfall is expected around 8am Friday in sparsely populated region between St Lawrence and Gladstone.

Peter Hannam, writing in the Sydney Morning Herald, describes how Cyclone Marcia took forecasters by surprise. He describes how meteorologists were tracking the storm at category 1 strength at midday Thursday, with sustained winds of just over 100km/h. But by about 4pm the forecasters noticed the cyclone slowing in speed and suddenly it rapidly gained in intensity. Data showed that projected wind speed for Marcia had leaped to as much as 230km/h, putting it into the category 5 range. The heat capacity was there in higher than average sea surface temperatures and upper air conditions allowed it to suck in more warm air from south east and increase its rotation. (See image of Pacific Winds feeding tropical cyclone Marcia bottom of this page) Slower movement of the cyclone, though more rapid rotation, provided the right conditions for a very rapid intensification to category 4 then category 5 levels catching forecasters, and most of the public, by surprise.

Marcia's Impact

Warnings have been issued for destructive winds, heavy rainfall, abnormally high tides and dangerous surf, for people in the Southeast Coast and parts of the Wide Bay and Burnett and Darling Downs and Granite Belt Forecast Districts. Locations which may also be affected include Warwick, Gold Coast, Toowoomba, the Lockyer Valley, Ipswich, Brisbane, Caboolture, the Sunshine Coast, Kingaroy and Gympie. A flood watch is current for these areas.

A dangerous storm tide of up to 2.5 metres is warned between Sarina and Double Island Point.

Open evacuation centres are stationed at Sarina Cultural Centre, St Lawrence Bowls Club, Yeppoon Cyclone Shelter and Gladstone Entertainment and Convention Centre. More than 100 state schools will be closed on Friday due to the arrival of Tropical Cyclone Marcia.

Just before 6am on Friday Police closed the evacuation centre at St Lawrence as it was not cleared for a Category 5 cyclone. Residents were taken to the evacuation centre at Sarina. Emergency Services have also evacuated more than 100 people on Lady Elliot island off the state's central coast.

Shortly after 7am, the new Queensland Premier Anastacia Palaszczuk warned residents in Yeppoon and Rockhampton area, directly in the path of the storm, to stay inside and take no risks.

"Over the next few hours, many thousands of Queenslanders are going to go through a harrowing and terrifying experience and I want those people to know we are with you every step of the way, we will be standing by your side," she said. "This is a severe cyclone, I want everyone to take all the precautions they possibly can take."

Update 11:30am Friday 20/2 AEST. Cyclone downgraded to category 4 with wind gusts of 250kph, 40kms north of #Yeppoon according to ABC News 24 (@ABCNews24)

At 1pm Friday Tropical cyclone Marcia had decreased in intensity to a Category 3 storm as the eye of the cyclone hovered over the regional city of Rockhampton for about 3 hours delivering 100mm of rain.

Initial report from AFP from Yeppoon damage to houses and flooding and 30,000 people without power in the area. Initial assessments are saying there has been significant damage to buildings in Yeppoon and Rockhampton. One person estimated a third of all houses in Yeppoon have suffered damage, according to ABC News 24.

7 news reports that Yeppoon hit hard by Cyclone Marcia. (Youtube)

It now seems some regional dams are filled to capacity and spilling on Friday night. This includes Gladstone's Awonga Dam. The automatic spill gates on the Callide Dam have opened and the toen of Jambin downstream is being urgently evacuated. Banana Shire Mayor Ron Carige told people in low lying areas of Jambin to evacuate to the school, according to ABC News.

Higgins stormchasing reports:
9PM URGENT ALERT for Jambin residents urged to evacuate to the Jambin State School due to high flood waters coming from Callide Dam. HSC is observing 10 meter rapid rises and inflows into Callide Dam.

A separate trough is bringing rain to northern NSW and south east Queensland with rainfall of over 200mm being recorded on the Sunshine coast since 9am Friday. Brisbane has received 50-50mm of rain. As Tropical Cyclone Marcia moves south it will interact with this trough system increasing rainfall and flash flooding around the creeks in Brisbane.

One hopes that everyone in the path of these storms are well battened down with their emergency kits.

It is the middle of the cyclone season and these are the first major cyclones to make landfall.

Cyclone Marcia Storm surge

Marcia crossed the coast about 8am, about 100km north of Yeppoon as a category five storm travelling south likely to pass slightly to the west of Yeppoon and weaken slightly to category 3 as it passes directly over Rockhampton. The storm surge was likely to be about 2.6 metres on top of a high tide occurring at 9am. At a second press conference (Youtube) around 10am Premier Annastacia Palaszczuk warned that storm surge may be as high as 3.0 metres and that Yeppoon would go into lockdown.

The European based Global Disaster Alert Co-ordination System (GDACS) provided a rapid escalation of the likely storm surge, as the intensity of the storm rapidly increased. An initial storm surge height of 0.6m was projected for Port Alma. This was increased to 1.2m twenty hours later. The estimated storm surge at 7am Friday was again increased to 2.1 metres in height based on the storm being (Australian) category 4 storm.

Based on advisory number 5 of tropical cyclone MARCIA-15 issued at 19 Feb 2015 18:00:00 (GDACS Event ID 1000145) GDACS provided the following impact estimate:

Population affected by cyclone-strength winds (>120km/h): 140,000
Saffir-Simpson Category: Category 3
Maximum sustained wind speed: 204 km/h
The maximum Storm surge height is 2.1m in Port Alma, Australia. This height is estimated for 20 Feb 2015 07:00:00.

GDACS also warned of heavy rainfall, flooding and flash flooding issuing orange alerts for these dangers.

Based upon eTRaP data provided by NOAA/NESDIS with reference date 19/02/2015 18:00 UTC, torrential rain is forecast reaching values between 200 and 250 mm with values between 17 and 25 mm/h. Medium likelihood for floods and flash floods is estimated. This includes for Brisbane, the Sunshine Coast and the Goldcoast as the cyclone works its way south over the coast.

Warmer than normal sea surface temperatures

One of the driving forces for the formation of Tropical cyclones and their intensity is sea surface temperatures. Here are the maps from the Australian Bureau of Meteorology Sea Temperature and Currents for the Northern Territory and Queensland showing why these cyclones can develop into severe cat 3 to cat 5 storms.

Here is the most recent 7 day global sea surface temperature anomaly chart, also from BOM Sea Temperature analysis page, showing warmer than normal waters right round Australia. But it is the tropical temperature waters in the Arafura and Coral Sea that really drives cyclone intensity and moisture uptake making for more intense storms.

Climate scientists have been telling us that when you warm the climate you get storms with greater intensity. While we may not be able to attribute any one storm as being associated with climate change, we know the basic conditions for their formation and fuelling are altering by a warmer climate system, particularly sea surface temperatures.

These severe Tropical Cyclones carry the risk to life and health of human populations, damage to houses and infrastructure, and damage to agriculture and food crops. The economic disruption can trickle through to the rise in fruit such as bananas which are transported to southern states.

Cyclone Yasi, as the previous category 5 storm to hit Queensland in 2011, caused extensive damage to the Great Barrier Reef according to research survey conducted afterwards and detailed in a report = Impacts of Tropical Cyclone Yasi on the Great Barrier Reef (PDF).

This report stated; "The damage from TC Yasi was extensive. Overall, coral damage was reported across an area of approximately 89,090 km2 of the Great Barrier Reef Marine Park. In total, approximately 15 per cent of the total reef area in the Marine Park sustained some coral damage and six per cent was severely damaged. Most of the damage occurred between Cairns and Townsville. Reefs beyond the northern limit of the destructive wind band (around Port Douglas) appear to have escaped severe damage, although tourism operators reported minor damage at some sites, especially those characterised by high cover of fragile branching and plate corals."

The economic damage caused by Yasi amounted to $800 million in damages, particularly to the roads and transport network, Agricultural production of bananas and sugar cane was particularly badly hit.

Simon Torok from CSIRO has published an interesting blog article today detailing five questions about tropical cyclones that you need answered. This details what the science says that cyclones in the south Pacific region are likely on average to reduce in frequency, but increase in intensity due to climate change. It also explains that rising sea surface temperatures and a warmer atmosphere mean more moisture can be carried, so increasing intensity of storm systems. Increased coastal flooding and storm surges are likely impacts.

Assessing the impact of extreme weather events like bushfires and cyclones on ecosystems is also very important. Readr Connecting cyclones and carbon emissions in our northern savannas on Mark Grant's blog. Cyclones can cause major damage to vegetation and carbon storage capability. Read the study at Environmental Research Letters: Impacts of an extreme cyclone event on landscape-scale savanna fire, productivity and greenhouse gas emissions (abstract)

Pacific Winds feeding tropical cyclone Marcia

A near real time map of surface winds from this site.

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