Specialty insurance and reinsurance firm Aspen Insurance has reported gross written premium of $495.6m for the third quarter of 2011, up 19.2% compared with $415.8m for the third quarter of 2010.

The company’s net income after tax was $22.2m or $0.23 per diluted share for the third quarter of 2011, which included $55m or $0.75 per diluted share of net losses resulting from the natural catastrophe events that occurred during the third quarter of 2011.

The net was also attributed to increases to loss estimates for the US severe weather related events that occurred in the second quarter of 2011 and the Japan earthquake that occurred in the first same year.

The company posted operating income of $56.5m or $0.70 per diluted share in the third quarter of 2011 compared with $72m or $0.79 per diluted share for the same period last year.

Aspen Insurance net income and operating income was down by 76.1% and 21.5%, respectively, reflecting the effect of catastrophes occurred in Japan and US during the year.

A decline of 32.6% was also seen in the underwriting profit, which was $26.7m for the third quarter 2011 compared with $39.6m for the equivalent period previous year.

The company expects gross written premium for 2011 to be unchanged from its last guidance at $2.1b plus/minus 5% with premium ceded between 11% and 14% of gross earned premium.