Sunday, March 26, 2017

A first glimpse at the 2017 hurricane season.


With a possible subtropical system developing in the Caribbean, the system could become named, it could even become a full born tropical system . I thought I would post some thoughts I have on the upcoming  2017 Atlantic Hurricane season. This isn't going to go into a lot of detail. There is still a lot of data that has to come in before I can state how things look to go. My official tropical outlook will be released most likely at the end of April.

The first day of the Atlantic Hurricane Season begins on June 1st.  So there is plenty of time to look at the data and trends.

Even though there isn't a lot to go by yet, looking at the current Sea Surface Temperatures (SST)can give us a clue and a few answers.

Here is a look at SST as of 3/26/2017; in it we can see two things. First, is the developing El Nino. The second is the cool water west of Africa, and warm waters off the East Coast of the US. 
 
 

 
 
 
 

The analog years I've been looking at are 1951, 1953, 1957, 1972, 1997, and 2015. Number 1 was 1972 and number 2 was 1997.
 


 
 
The Pacific:

Looking at the tropical Pacific, we see warming in ENSO regions one and two. The current ENSO neutral conditions look to continue for the rest of Spring, then we will transition toward El Nino this Summer , and most likely be in an El Nino this Fall.

History tells us that El Nino's typically inhibit Atlantic tropical activity. The warm SST in the Pacific causes the air to rise over the tropical Pacific. Since weather in the Northern Hemisphere tends to go west to east, that  warm rising air in the Pacific sinks over the Atlantic; this helps stabilizes the atmosphere over the tropical Atlantic. More in the way of stable air leads to less in the way of thunder storm activity.  El Nino's  also tend to cause stronger winds to come off of Central America, these winds extend into the tropical development zone of the Atlantic. The winds shear the tops off of developing tropical cyclones, making it harder for hurricanes to develop. During El Nino years we also tend to see the Atlantic trade winds blow faster. This causes any thunderstorms that do develop to move faster , again leading to fewer hurricanes.

It is still uncertain if El Nino develops, or if it does if the atmosphere will respond quick enough to make a difference.

The Atlantic:

We have cool SSTs west of Africa in the prime development zone.  Tropical cyclones need warm SST's in order to develop. Cooler tropical waters lead to unfavorable hurricane conditions. This along with a developing El Nino means  long track Cape Verde tropical systems will have a hard time this year.

This time of year it's hard to make long term predictions. Why? Because this time of year is always a time of transition.  

 ACE:

It's becoming obvious that the upcoming season will have less ACE points than we saw in 2016.

An article by Weatherbell's Joe Bastardi was shared to me. Here is a few graphics from Bastardi's post. These will prove the point I'm making.
Image credit Joe Bastardi, Weatherbell Analytics
Mean sea level pressures of the 1950's
Image credit Joe Bastardi, Weatherbell Analytics
mean sea level pressure from 2006 to 2016
Image credit Joe Bastardi, Weatherbell Analytics
Image credit Joe Bastardi, Weatherbell Analytics
Image credit Joe Bastardi, Weatherbell Analytics

In the images you can see the warmer than normal SST off the Southeast U.S. and Caribbean

Colder than normal SST off the Northeast and North Atlantic.

So you have higher pressures in the north and lower pressures in the tropical development zone of the Atlantic .

Mean sea level pressures of the 1950's were higher than normal in the north, normal in the Atlantic, and lower than normal in the Caribbean. 

All of this causes tropical storms to  come close to the U.S. Southeast Coast and move up the coast.

SST and mean sea level pressure from 2006 to 2016. This period has seen no official major hurricane strikes on the East Coast, (But I personally count Sandy as a major hit, based on her impact).  
 

This year will have some similarities to last season.

The SST's are warmer off the East Coast into the Caribbean and Gulf. So, any tropical systems that do develop will develop on the western side of the Atlantic. The closer the storms form to the U.S. the greater the odds for landfalling tropical cyclones on the East and Gulf Coast of the U.S.

My early thoughts on the upcoming hurricane season  is for a average to slightly below average season. Something similar to1972, 1997, or 2015. So  I'm leaning toward 10-12 tropical systems, with 3-4 hurricanes with 1 major hurricane.

The warmer waters off the East Coast, would also help tropical systems retain strength or even intensify as they move up the coast. This would be worrisome, because the impacts could be similar to what we saw during the 1950's.   

That's it for now.


 


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