Paul’s Low Headed Back to Gulf of Carpentaria

The Australian Bureau of Meteorology (ABM) continues to monitor the low pressure system that was tropical storm Paul. The ABM issued an update on Paul’s low at 4:56 p.m. CST local time (3:26 UTC), Wednesday, March 31, which would be 11:26 p.m. on March 30 for U.S. Eastern Daylight Time (the U.S. East coast is 14 1/2 hours behind Darwin, Australia’s time). Paul’s center was still over land on March 31 but is forecast to move into the southwestern Gulf of Carpentaria on April 1.

As a result, there is now a cyclone Watch in effect for coastal and island communities from Cape Shield to the Northern Territory/Queensland border, including Groote Eylandt. The Cyclone Watch from Nhulunbuy to Cape Shield was cancelled. However, there is a Severe Weather Warning for damaging wind gusts and heavy rainfall in the Roper-McArthur and Arnhem Districts.

TRMM captured a satellite image of Paul’s rainfall on March 30 at 1707 UTC (1:07 p.m. EDT). At that time, Paul’s rainfall was mostly light to moderate (between 20 and 40 millimeters or .78 to 1.57 inches per hour) over land and the isolated areas of heavy rain (as much as 2 inches per hour) were confined over the waters of the Gulf of Carpentaria.

Having been hit by two tropical cyclones so far this season, Queensland had been the center of tropical cyclone activity, but with the recent arrival of Tropical Cyclone Paul, it is now the Northern Territory’s turn to experience heavy rains and gusty winds.

Paul originated from a low pressure circulation embedded within the monsoon trough over the Arufura Sea between the northern coast of Australia and New Guinea. As the circulation drifted southward towards northern Australia it intensified slowly and only became a Category 1 cyclone on the evening of March 28, 2010 (local time) when the center was right over the northeast coast of the Northern Territory where it brought wind gusts of up to 110 kph (~70 mph, equivalent to a tropical storm on the US Saffir-Simpson scale).

TRMM data was used to create a 3-D perspective of the storm from data from TRMM’s Precipitation Radar instrument. The most prominent feature is a deep convective tower, which penetrates up to 9 miles (15 km) high. This corresponds with an area of intense rain in the northwestern eyewall evident in the TRMM’s image of horizontal rainfall. These tall towers are associated with convective bursts and can be a sign of future strengthening as they indicate areas where heat, known as latent heat, is being released into the storm.

This heating is what drives the storm’s circulation. Despite Paul’s proximity to land, it was able to intensify into a Category 2 cyclone (equivalent to a minimal Category 1 hurricane) by the following morning with wind gusts of up to 140 kph (~85 mph). Paul is hovering over land along the coast and is expected to weaken slowly over the next day or so; however, it could eventually re-emerge over the very warm waters of the Gulf of Carpentaria and re-intensify.