Tropical Storm HeleneAdded : Friday at 16:25 The meteorologists out there would have seen this little feature showing up on the models a few days ago. It's not like we've ignored it, or decided not to say anything about it. But, in our science, we know there are certain features that models handle badly. We tend to wait until there is either consensus or continuity in the forecasts before taking a closer look.
OK, here is Tropical Storm Helene at the moment :-
Previous model runs struggled with Joyce which is nearby and a sort of Fujiwhara effect between the two of them. By tomorrow, Helene moves North and catches a ride on the upper level winds :-
At this point, Helene is still a symmetric warm core low (i.e tropical) based on the mesoscale GFS ► model :-
By Saturday, Helene is by herself out in the mid Atlantic affecting the Azores as a rather potent Tropical Storm. At this point though, the system begins to switch to an asymmetric warm core low which means that the process of extra-tropical transition is well underway. Also, the upper level steering becomes far more fragmented as an incoming upper trough begins to draw Helene into the circulation :-
This is where most of the models start to disagree and for good reason. Some models take Helene East towards Portugal, whilst some take remnants of her across Central and Southern England. The main model cluster though absorbs her into the primary low circulation and takes her West across Ireland or a little further to the West of Ireland.
The GFS ► at the moment brings Helene into the Southwest approaches on Sunday night :-
At this point, the system is completely extra-tropical with cold core characteristics.
So, an interesting little system and we will take a closer look at this over the weekend.
METEOROLOGIST : MARSH |