The Atlantic
Hurricane Season runs from June 1st through November 30th.
Sea Surface Temperatures (SST):
The sea
surface temperatures in the eastern tropical Pacific are still cooler than
average. Things are similar in the
Atlantic Basin. The eastern Atlantic off the coast of Africa is cooler than
average, while the western Atlantic, Caribbean, and northern Atlantic are
warmer than average.
Four above images courtesy of WeatherBell Analytics.
El Nino Southern Oscillation (ENSO):
The ENSO
plays a huge role in tropical cyclone activity in the Atlantic basin. The
question many are asking is will we see La Nina, El Nino, or neural conditions
in the tropical Pacific? The 2017
hurricane season featured a weak La Nina, as a result last year's season was
twice as active compared to average.
While the Sea Surface Temperatures ( SSTs) in the ENSO zones 1/2 and 3
are cooler than average; we have seen SSTs start to rise over recent weeks.
Above images courtesy of the Climate Protection Center
Atlantic Multidecadal Oscillation (AMO):
Looking at
the SSTs in the Atlantic. The AMO is in a transition, looks to be turning into
a negative phase. Typically during a negative phase tropical activity in the
Atlantic Basin is lessened. This is because the SST in the Main Development Region
(MDR) are cooler. But there have been exceptions. Last year was a hyperactive
season. But most of the tropical cyclones formed outside the MDR. This could be the same for this season,
because those cooler SSTs off the West Coast of Africa are cooler than average.
1951,1954,
1976,1996,1997, 2006,2014
These are
the analogs I came up that resemble the current conditions with respect to SST,
geopotential height and sea level pressure patterns around the world. 1951 and
2006 are the two closest matches.
I think
we're going to see the La Nina conditions make a transition to an weak El Nino,
most likely a El Nino Modoki. El Nino years typically result in fewer tropical
cyclones forming in the Atlantic Basin. But a Modoki is different. Instead of
forming in the eastern Pacific it forms in the Central Pacific. This subtle
difference allows for a higher storm frequency, it also appears to increase the
odds for Tropical Cyclones impacting the Gulf of Mexico.
Accumulated Cyclone Energy (ACE):
ACE is a
mathematical formula that is used to judge how much wind energy will be
available for tropical storm development for the entire season. The higher the
number the greater the chance for increased hurricane activity and stronger
hurricanes. Basically ACE is a blend of
the number, strength and duration of tropical cyclones , in an effort to
determine how destructive the season could be. 2017 ended up with an approximate ACE of about
226. Here is a chart showing the top 10 ACE Atlantic hurricane seasons.
Based on my
thoughts of a weak El Nino or Modoki forming by the heart of hurricane season
ACE will be much lower than last year.
50-85 is my call.
End Result:
As far as
Impact, last year we had a very active year with 17 named storms, 10
hurricanes, 6 major hurricanes As I said
in last year's tropical outlook, the US coast saw several landfalls , Cindy,
Emily, Philippe and Nate, including two major hurricanes Harvey and Irma.
For 2018
things shouldn't get as intense. But we're going to still be at risk of
tropical cyclones in the western Atlantic and Caribbean. I think the East Coast will be at less risk
than last year for tropical impacts, with many of the Atlantic storms staying
east of the US East Coast. But for the Caribbean into the Gulf of Mexico there
will be a greater risk for tropical mischief, due to my thoughts on a Modoki El
Nino developing.
The number
of named tropical cyclones will be 10-13, 5-6 will become hurricanes, 1-2 will
become major hurricanes (category 3,4,and 5). There will be a risk for 1-2 US land falling storms especially in the Gulf
of Mexico.
Summer thoughts:
It was a
cool spring. When we look at past years,
Temperatures that were below average in April lead to cooler than
average Mays. The current pattern would support the validity of that idea.
PDO:
The warmth
off the West Coast will help promote a ridge over the west and a trough in the
East.
When we look
at the analog years, they would suggest temperatures in the Northeast would be average to slightly below average
for the June through August timeframe.
At the same time precipitation amounts would be average to slightly
above average.
Soil
Moisture is above average for this time of year. All the moisture will give us a nice buffer
when we enter Summer. High levels of
soil Moisture tend to lead to less heat waves.
I don't
think it will be an excessively hot Summer with severe drought problems in the
Middle Atlantic and Northeast.
Things very
well could turn cooler for the end of September into October.
