Weather@home: Mexico

As part of the RECLIM-UK (Regional Climate Projections Initiative Mexico – UK) project in which University of Oxford, UNAM, CICESE, and LORAX are partners, and sponsored by the British Council, we are now investigating the influence of the anthropogenic activity on the anomalous winter season over the northwest of Mexico and the anomalous wet summer 2005 over the southeast of Mexico.

Figure 1. Seasonal precipitation (mm d-1) in the NAM [North America Monsoon] core region (from CLICOM dataset)

Winter 2004 was a very wet winter in California and in the core of the North America Monsoon (NAM) region – the 2nd wettest in the last 30 years (Figure 1), whereas summer 2005 was one of the driest monsoon seasons in Mexico, with very few hurricanes in the Eastern Pacific.

Figure 2. Tropical system’s trajectories during the 2005 hurricane season over the Atlantic (data from the National Hurricane Center, image from Wikipedia)

However in the Atlantic, summer 2005 registered the most active hurricane season (Figure 2), with 15 hurricanes (the mean for this basin is 6 hurricanes per year). Wilma, the most intense hurricane of this basin, in terms of wind speed, made landfall in Cancún, causing structure losses in Cancún estimated at between $2 to $5 billion dollars (as reported by Crawford & Co.).

Hurricane Stan produced heavy rainfall events in Veracruz and flash floods in large parts of south of México and Central America. The continuous passage of the tropical cyclonic systems during 2005 on the Gulf of Mexico translated into one of the wettest years in Veracruz and in the last 30 years (Figure 3). Hurricane Katrina made landfall in the east coast of USA, producing claim insurance losses estimated at $71  billion dollars. The total losses of that year after the passage of Katrina, Rita and Wilma were estimated at $117 billion dollars (as reported by Swiss Re).

Figure 3. Total annual  precipitation  in Veracruz, Veracruz and Tapachula, Chiapas (from CLICOM dataset)

The oceanic-atmospheric system during the winter of 2004 were those of a very weak El Niño and during the summer of 2005 those of a very weak La Niña, therefore ENSO [El Niño Southern Oscillation] does not explain per se the extreme rainfalls over the monsoon region during the winter, nor the intensity and number of hurricanes over the Atlantic in summer 2005. Hence we want to investigate the role of the anthropogenic activity on this particular period.