Applied to CMIP5 data, significant TC formation distribution errors were apparent for a number of models, including frequent formation in the South Atlantic and eastern South Pacific (where TCs rarely or never form), and a lack of TC formation in the central North Atlantic. Those southern regions are in reality too dry (RH700<40%) for TC formation, but are moist in the models, allowing frequent formation. The opposite is true in the central North Atlantic where TC formation is frequent in reality, but too dry in the models.
Results from seven models with good southern hemisphere TC formation distributions, are being analysed for changes in TC formation boundaries between the historical (1970—2000) and future (2070—2100, RCP8.5 scenario) climate. Preliminary results suggest little change in the boundaries will be identified, except in the eastern South Indian Ocean basin where there is general consensus between the models of an equatorward migration of the RH700 boundary that will thin the already narrow latitudinal band in which TCs form. Reduced TC detection numbers in this region support the result.