Tropical Weather Discussion 6/12-6/18

It’s early in the 2017 North Atlantic Hurricane Season.  The season officially began on June 1, but Tropical Storm Arlene developed in April so the next named storm will be Bret.  This list was previously used during the 2011 season.  The list of names for this season is listed below.  Irma is on the list for the first time, replacing Irene.  Irene was retired due to the extensive damage she caused throughout the Atlantic basin.

On average, 1 tropical cyclone develops in June every other year.  These systems tend to develop in the Western Caribbean Sea or the Gulf of Mexico.  Occasionally storms will develop in the SW Atlantic Ocean at the tail end of a frontal boundary that stalls.    Usually, a weak tropical wave will pass without incident through the Atlantic and Eastern Caribbean before reaching the warm waters of the Western Caribbean Sea.  For a variety of reasons, this area is favorable for Tropical Cyclone development.

Tropical Cyclone Origin and Tracks June 11-20 (image NHC)

The first reason why this area is favored is Sea Surface Temperatures are well above the 80 F threshold generally required to generate tropical cyclones.   Another reason is the shape of the coastline in Central America.  The concave nature of the coast allows for thunderstorm development.  The warm waters then allow low pressure to form and a TC is born.   Here are the current sea surface temperatures in the Western Caribbean and the Gulf of Mexico.

Sea Surface Temperatures 6-11-17 8 PM (image Weatherbell)

The brown/gray hue in the Bay of Campeche and the Gulf of Tehuantepec is interesting.  Looking at the visible satellite we see a well-defined circulation in the Gulf of Tehuantepec moving NW into Mexico.

NOAA GOES_East Wide Atlantic Visible Satellite

That feature is  Tropical Storm Calvin.  This will move inland and drop 10-15″ of rain in Southern Mexico.  Although the circulation will dissipate over Southern Mexico, lower than normal pressures will remain in the Western Caribbean and Gulf of Mexico by the end of this week.  There will be a chance at development early next week in the region.  The ECMWF (Euro) and the GEM (Canadian) are the most bullish about TC development at this time.  It’s early, but it will have to be tracked over the next 5-7 days.

The EURO is hinting at a weak tropical wave developing but it’s way too early for storms coming off the West Coast of Africa.  This Tropical Weather Outlook blog will occur more regularly as we get deeper into the heart of Hurricane Season.  I’ll check back in this weekend with some additional thoughts.

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