SUBTROPICAL STORM IN MID APRIL! what if anythign does it ” mean” for 2017 Hurricane season
In case you didn't notice... and by judging from some the reactions you probably have not... a subtropical storm has formed the middle of the Central Atlantic Ocean in the last 12 to 24 hours. While this is a unusual occurrence it's not completely unheard of. We have seen subtropical storms form in mid April in 2003... 1973... 1981 ...and 1992. Most of them have formed in the middle of the Atlantic Ocean and were at one point a large ocean LOW that become trapped and changed from a cold core to a warm core system. Indeed this is exactly what has happened with this system over the last two days.
These visible satellite pictures clearly show the system with the low level circulation but with most of the convection is on one side of the system. It clearly has a frontal boundaries associated with it so it's not completely warm core the but it is also structured somewhat differently from the typical north Atlantic large LOW pressure area.
The midday hurricane models show the system doing a whole lot of nothing as a gets trapped and overwhelmed by the next large Atlantic LOW which is about to form to its northwest.
The WED morning European model shows the position of the subtropical storm early Thursday morning in the Central Atlantic Ocean but a strong front is clearly diving into the system and absorbing it. By Thursday night / Friday morning the tropical system center is filling rapidly and a new deep LOW pressure area has developed to the west and is clearly absorbing the subtropical system. And by Friday night / Saturday we have a large typical new LOW Pressure area in the central north Atlantic which has completely absorbed the sub tropical Low.
Perhaps the next question that comes to mind is what if anything does a early season tropical or subtropical system mean with respect to the upcoming hurricane season? There is actually has no significance of any kind. Of course that doesn't mean you are going to see the typical weather hucksters try to convince you that there is some sort a connection between this of subtropical storm and the upcoming hurricane season. But as you can see from the data there is nothing indicating that whatsoever.
In fact the only tendency that I can see or trend is that if we look at these four seasons we will see that there was a strong bias for hurricane activity to stay away from the Gulf of Mexico and the East Coast and be centered over the central and or eastern portions of the North Atlantic Ocean.
We can start out by taking a look of the 1973 hurricane season. There was a early season subtropical LOW in the middle of the north Atlantic in April. The overall hurricane season at 17 named systems but only one of them was of any significance and there was no activity of any kind worth noting in the Gulf of Mexico Florida or the East Coast. In fact the vast majority of all the activity was over the central and far eastern Atlantic.
In 1981 there were two early season April systems both the which were classified as tropical depressions and both of them were in the Caribbean Basin. For the season there are 22 different systems that featured three significant hurricanes but no significant U.S. activity or landfalls. The vast majority of the systems in 1981 curved out to sea quite early.
In 1992 there was a subtropical storm in mid April in the Western Atlantic Ocean which did absolutely nothing in terms of development. The season featured 1 name systems with one category 5 Hurricane Andrew. Again however the vast majority of the activity was in the central and Eastern Atlantic Ocean
And finally in APRIL 2003 a tropical storm did form in the central Atlantic and it tracked east towards the Azores in the middle of April. There were 21 name storms that year which feature one category 3... one category 4 ...and one category 5 hurricane ISABEL . Only hurricane Isabel was of any significance to the U.S. And the vast majority of the systems again stayed out across the central and Eastern Atlantic Ocean.