Leslie And The ACE IndexAdded : Tuesday at 15:25 Tropical Storm Leslie... Yep, we mentioned this last week and we will probably be mentioning it next week too...
Here she is out in the mid Atlantic :-
Not really the most impressive system to look at, even the satellite image isn't anything too exciting :-
What is rather impressive though is the longevity of the system and how global models keep it still out in the mid Atlantic 10 days from now. Here is the T+240hr chart for 10 days time :-
You see, Leslie is stuck between what meteorologists call a rock and hard place. She sits in the middle of two large upper ridges with very little steering. She is also a little too far South to be caught in the upper Westerlies which means she meanders around doing very little for the next week or more.
So what does the ACE index have to do with this? Well, hurricane seasons are constantly monitored and the ACE index (or Accumulated Cyclone Energy) is a handy way of knowing just how active a season has been.
At the moment, the season is running a little above average with an ACE index of 88 (84 being the average for October 1). It should come as no surprise that the system which had the most ACE this season so far in the Atlantic was Hurricane Florence which was a named storm for 15 days, a hurricane for 8 days and a major hurricane for nearly 4 days and generated an ACE score of 37.5.
Global models point to Leslie intensifying into a hurricane in the next few days and it will be interesting to see what her ACE score is this time next week.
The strange thing is that aside from generating swells which are affecting coastal areas on the East coast of the USA and Bermuda, Leslie in fact stays well out in the Atlantic doing very little for the next week or so.
So, whilst the ACE index of the 2018/19 season could end up above average, it will be interesting to see what proportion of that score was given to a system which stayed out in the big pond minding its own business for over a fortnight.
METEOROLOGIST : MARSH |