Tropical Thoughts on Bob and Danny

Happy Hurricane Bob Day! For many it is a not so happy anniversary but it has been 24 years since the tropical cyclone stormed through Buzzard's Day with 105 MPH winds and 12-15 ft of storm surge.  Let's look back at Bob and take a look at Tropical Storm Danny way out in the Atlantic.  Please see my post from Saturday on my overall late August look at the tropics.

Hurricane Bob August 19, 1991
Bob developed in the Bahama's on August 16, 1991.  It was spawned by a cold front that exited the East Coast and degenerated.  The storm quickly intensified and moved north passing about 35 miles east of the Outer Banks.  The forward motion increased as Bob strengthened into a 115 MPH Category 3 Hurricane.  Cool ocean waters south of New England prevented Bob from keeping this strength (note- not the case this year see below).  Still on August 19 Bob roared into SE New England.   East of the center had very little rain but strong storm surge and strong Category 2 strength winds.  West of the center saw heavy rain.  This is the case with nearly all tropical cyclones due to the counter clockwise circulation.
NWS Boston Hurricane Bob graphic- from NWS Boston twitter feed
Although we faced considerable impacts from Floyd, Irene, and Sandy New England has not faced a direct Hurricane hit since Bob.  Are we due?  There is no such thing.  It all comes down to a combination of atmospheric/oceanic factors.  As you can see in my post from Saturday between 1938-1960 there were 5 direct Hurricane hits, not to mention the extreme flooding from Diane in 1955.  Even if the New England hurricane drought continues another 50 years we will always face a threat between August and October.

A 2013 report by insurance adjusters, in conjunction with the Great Hurricane of 1938's 75th anniversary, concluded that if Bob hit in 2013 it would have caused $35.4 Billion in damage, compared to $1.5 billion in 1991.  The coastline is super developed with valuable property.  Buzzards Bay is particularly vulnerable to storm surge.  Let's also consider that it took several communities 5-7 days to get power back from Irene.  What would a full fledged Hurricane do?

August 19, 2015 Tropical Update
Tropical Storm Danny formed yesterday in the open Atlantic Ocean.  Winds are currently 50 mph with a pressure of 1000 mb.
NHC 11 am est Advisory Tropical Storm Danny
The NHC thinks Danny becomes a Hurricane on Friday.  We'll see but the fact that the storm is small will help.  There are some unfavorable atmospheric factors in Danny's way.  Some guidance suggests these will subside.  First off on infrared satellite the storm does not have much deep convection with it (though it appears to have good structure).
GOES_East Rainbow IR satellite loop (NOAA)
The system may be pulling dry air into its circulation.   Also wind shear is evident in front of the storm.  The water vapor loop very dry air to the north along with strong wind shear.  This is typical of El Nino years in the Atlantic Ocean. 
GOES_East Water Vapor Loop (NOAA)
Let's see where Danny actually ends up in 5 days.  If it looks to be heading north of Puerto Rico it is something to really watch.  If it heads in the Caribbean I cannot see it surviving the hostile environment there.  The shear has been strong all season.  The storm looks to be small so the circulation would be ripped apart by the mountains.  But again if it can get in the SW Atlantic sea surface temperatures are favorable.
North Atlantic SST Anomalies (image Weatherbell)
I'll keep an eye on it.  Enjoy the cooler temps today and tomorrow.  Update on the weekend forecast plus Danny tomorrow.

-Zack Green


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