Peak of Huricane Season Approaching, Any Action?

The vast majority of tropical cyclones that impact New England occur in August and September.  There have also been a few in October, most notably Sandy in 2012.  We have seen impacts in July and November as well (Arthur 2014, Noel 2007) but the highest potential for a strong storm is now. 

Personal Table of New England Storms of note

Irene was a tropical storm that dropped tremendous rain on Vermont and its winds knocked down thousands of trees and power lines in Eastern New England.  Power was out for 5 days for many areas in MA/RI.  That was eye opening as the past tells us much stronger storms have impacted the region.  These storms bring a variety of impacts to the region.  The Hurricane of 1938 is the GOAT as it hit without warning, at high tide, moving at 50+ MPH with sustained winds of 120 MPH.

Woods Hole, Hurricane of 1938 (image NOAA/NWS Boston)

Westerly, RI Brightmans Pond (Providence Journal, NWS Boston)

Here is the NWS Boston's overview of the storm put together in 2013 for the 75th anniversary of the storm.  The good news is that nothing in the Atlantic Ocean at the moment is even remotely capable for producing a storm like that.  In fact it has been a very quiet season with only 3 named storms.  Ana formed in May, Bill in June, and Claudette in July. 

2015 Atlantic Hurricane Season tracks (wikipedia)

All of the storms have formed close to land.  Why would that be?  In the Pacific Ocean a strong El Nino event has developed and that has enhanced tropical cyclone activity in that basin while suppressing activity in the Atlantic.  Here is the sea surface temperature anomaly chart.

OSPO Sea Surface Temperature Anomaly Chart 8-13-15

It's not hard to pick out the warmth in the Pacific.  While the Atlantic looks to be favorable strong winds aloft are ripping across the Caribbean Sea into the Eastern Atlantic.  Here is a graphic off the GOES_East satellite to illustrate the point (taken from the spaghetti model web page)

University of Wisconsin wind shear tendency chart

Although the wind shear relaxes a bit in the central Atlantic there is still dry, dusty air out there.  The dust comes from the Sahara Desert.

University of Wisconsin Meteosat-9 Saharan Air Layer

There are some waves trying to eat away at this dry air.  They will have a tough time but its possible one or two can form into a Tropical Cyclone.  In 1997 a major Hurricane was able to form in early September from a wave near the Cape Verde Islands.  1997 was the last time we saw an El Nino event this strong so it works a good analog. 

August 16, 1997 Sea Surface Temperature Anomaly (OSPO/NOAA)

Although there are differences, the general appearance remains the same.  Hurricane Bob was able form in 1991 during an El Nino.  It formed in the Bahama's and strengthened as it moved up the east coast. The weather pattern in week 2 appears to favor tropical development off the east coast and several global models and ensemble products indicate this.  I AM NOT PREDICTING A STORM LIKE BOB.  I am merely saying there could be "Danny" near the United States in the 6-10 day period.

RMOP Friday August 21, 8 PM

One thing that favors tropical development near the United States is a persistent ridge of high pressure in the NW Atlantic.  If some thunderstorms can get under this ridge they are usually blocked from moving anywhere too quickly.  Waters are warm near the East Coast so an area of low pressure forms and off we go.  The top analog according to the 6-10 upper air pattern is August 27, 1962.

CPC 6-10 upper air analog

We find Hurricane Alma forming in the Bahama's on August 26, 1962.

Hurricane Alma, August 26-30 1962

The 1962 Hurricane season was very quiet, much like 2015 thus far.  New England was also in a drought in 1962 so Alma brought a lot of beneficial rain to the region. 

Hurricane Alma rainfall (NHC/NOAA)

Of course the next analog on the list is August 13, 2002 and no storms are found in that time period.  The third date on the list is August 30, 1952.  Here we find Hurricane Able which formed from a tropical wave but did not really strengthen until it got under the ridge in the western Atlantic.

Hurricane Able August 18-September 3, 1952

In summary the Atlantic basin has been quiet which is consistent with strong El Nino events.  We are entering the time of year where New England sees its strongest tropical cyclones.  The week two upper air pattern seems to favor an atmospheric environment where a tropical system could (should?) form near the US.  Just something to keep an eye on.

For part 1 of today's post on the heat/humidity please click here.

Thanks for reading
-Zack Green