Ra iv/hc-xxxii/Doc. 2(1), p. World meteorological organization
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| The fact that the system generates deep convection and wind force above 50 kts around a center that shows an eye-like structure is not enough for this storm to be considered a tropical cyclone; even if it shows some sign of warm core, that is again usual for autumnal mid-lattitude cyclogenesis over the ocean (and also in Mediterranean see), when the ocean is much warmer than the air mass involved in the low pressure area.
Above this meteorological fact, we must not forget that the number of tropical cyclones during a season is a number on which people focus more and more with climate change (even if there is better mean to qualify and quatify the activity), specially when we have to deal with the problematic of “more cyclone or not with global warming”. What if a cyclogenesis like grace’s one after the 1st of December? 
So, this hurricane season shows us that, once again, it is important to stick and perhaps to be clearer with the definition of a tropical cyclone for the 2 reasons mentioned in this document (Tropical Cyclone: A warm-core, non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and closed surface wind circulation about a well defined centre.) -if the term “non frontal” is not enough to make a difference between tropical mechanism and mid-latitude mechanism with upper level forcing we have to think to be more precise. -As Ana and Erika told us, we have to track a tropical cyclone even if the center is not well defined ( see below the examples of discussion about Erika.) “AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS BEEN SEARCHING FOR THE CENTER OF THE TROPICAL STORM OVER THE PAST FEW HOURS. THE CIRCULATION HAS BECOME QUITE DISORGANIZED. BUT IT APPEARS THAT THE CENTER HAS REFORMED TO THE SOUTHWEST OF THE PREVIOUSLY ESTIMATED TRACK. HOWEVER THE FLIGHT-LEVEL WINDS SUGGEST THAT THERE MAY BE MULTIPLE CENTERS. SO THE ADVISORY POSITION IS HIGHLY UNCERTAIN AND PROBABLY REPRESENTS A MEAN CENTER. OR THE LOCATION OF THE LOW-LEVEL VORTICITY MAXIMUM.” “VISIBLE SATELLITE IMAGES AND AIR FORCE RESERVE HURRICANE HUNTER DATA SHOW THAT ERIKA IS A POORLY ORGANIZED SYSTEM. THERE ARE MULTIPLE SWIRLS APPARENT ON THE SATELLITE IMAGERY ROTATING IN THE LARGER CIRCULATION ENVELOPE WITH A MEAN CENTER TO THE WEST OF THE DEEP CONVECTION. _________ Directory: pages -> prog -> www -> tcp -> Meetings -> HC32 -> documents documents -> World meteorological organization Meetings -> World meteorological organization Meetings -> Review of the ra IV hurricane operational plan Meetings -> Review of the past hurricane season Meetings -> Review of the past hurricane season documents -> World meteorological organization Download 8.37 Mb. Share with your friends:
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