Yasi Cyclone

Pre-Landfall 1 | Summary
Posting Date: January 31, 2011, 12:00:00 PM

As of the Australia’s Bureau of Meteorology 11:00 EST advisory, Cyclone Yasi is about 1630 kilometers east northeast of Mackay and moving west at 30 km. Gust wind speeds are currently 205 kilometers per hour. A cyclone watch is in effect for 900 kilometers of Queensland’s coast, stretching from the island communities from Cooktown to Yeppoon and inland between Georgetown and Moranbah. Yasi, which only became a cyclone on Saturday, strengthened rapidly since its formation. On Sunday, the storm passed north of Vanuatu, bringing strong winds and high waves. Presently, Yasi—a moderately-sized storm with cyclone-force winds extending outward 55 kilometers—remains over seas with warmer-than-average surface temperature and is experiencing low-to-moderate wind shear conditions. While in this favorable environment, the storm should continue to gradually strengthen, possibly nearing Category 4 strength by Wednesday afternoon when it is forecast to make landfall in northern Queensland. Queensland is in serious danger of another round of extreme flooding this week. In addition to the storm's damaging winds and storm surge, Yasi will bring torrential rains to already saturated soil. Although cyclone Yasi is currently expected to impact areas to the north of Brisbane and areas heavily flooded earlier in the month, a more southerly turn in storm track could dramatically change the flooding potential. Precipitation estimates are on the order of 200-400 mm with amounts as high as half a meter are possible. A moderate forward speed of 30 km/h should limit the most extreme precipitation scenarios. The latest TRMM (Tropical Rainfall Measuring Mission) meteorological data indicates rainfall rates near 20 mm/hr in the eye wall and 200-400 mm in the wake of the storm. Storm surge also poses a threat, particularly if Yasi strikes at high tide. In Townsville, the difference between low and high tide is about 3 meters while in Cairns, it is as high as 3.5 meters. The final surge heights will depend on the state of the tide. The extent of any damage will largely depend on Yasi’s future track and intensity, about which there remains some uncertainty. Most of the forecast models have Yasi passing between Innisfail and Mackay. The BOM’s most likely track, however, indicates that Yasi will pass to the east of Bowen and Proserpine. The coastal cities of Cairns and Townsville (150 and 200k residents respectively) are both forecast to experience destructive or very destructive winds from Yasi. In comparison to Cairns and Townsville , the area that lies in-between these two cities is not as populated, meaning that the wind damage potential could be moderate if Yasi makes landfall between the two cities. However, if the scenario takes Yasi toward either regional city, the wind damage could be significant. At Category 3 or 4 wind speeds, damage is expected to be significant. Structural damage to houses and buildings may occur, particularly to rooftops, while windows and cladding on engineered structures could be damaged by impact from debris. Many trees will likely be uprooted and snapped, blocking roadways or damaging homes and automobiles. However, strong building codes have been in place since the 1960s in north Queensland, and they will help mitigate the effects of high winds and associated debris. An especially strong La Niña event is affecting Australia, bringing precipitation-induced flooding and increasing the frequency and potential intensity of cyclones, due in part to near record-level sea surface temperatures north of Australia. As reported in the latest BOM climate statement and flood summary, the past four months (September - December) have been the rainiest such period in Queensland's history. Comparisons to Cyclone Larry, a powerful 2006 storm that wrought AUD $1 billion in damage, are inevitable. The track of Larry and the forecasted track of Yasi are quite similar; however, Yasi will likely be a larger, but a somewhat less intense storm. The AIR Tropical Cyclone team will continue to monitor the storm and provide updates as warranted.

Pre-Landfall 1 | Downloads
Posting Date: January 31, 2011, 12:00:00 PM