Invest 90L Likely to Become a Tropical Depression or Tropical Storm in the Caribbean

November 16,2016
A tropical depression or storm is likely to develop in the Caribbean Sea late this week or this weekend in what may be the final chapter of the 2016 Atlantic hurricane season.
(MORE: How the 2016 Hurricane Season Stacks Up, So Far | Hurricane Central)
Clusters of showers and thunderstorms associated with a broad area of low pressure have been intermittently flaring up the past couple of days in the southwest Caribbean, between Central America and Jamaica. This is an area that is a typical hotbed for November tropical cyclone activity, and forecast guidance has suggested the potential for development in this area for many days.
The NHC has designated the area of disturbed weather "Invest 90L". This is a naming convention used to identify features they are monitoring for potential future development into a tropical depression or a tropical storm.
(MORE: What is an Invest?) 

Current Satellite Image: Caribbean Sea

Sea-surface temperatures in the southwest Caribbean Sea are running about 0.5 to 1.5 degrees Celsius above average for this time of year, according to a NOAA/ESRL analysis.
Also, wind shear – the change in wind speed and/or direction with height that typically rips apart tropical disturbances trying to become depressions – is at a minimum over this area of disturbed weather.
Both of those factors are favorable for the possible development of a tropical depression or storm in the days ahead.

Current Satellite, Wind Shear

The NHC has given Invest 90L a high chance of development into a tropical cyclone within the next five days, most likely occurring during the weekend.
(MORE: 4 Reasons Why It's Not Time to Put Your Hurricane Kit into Storage)

Area of low pressure may develop in the western Caribbean late this week.

If a tropical depression or storm does form over the weekend, it's not clear yet if it would simply sit and stall in the southwest Caribbean Sea, move westward into central America, or stay over water for a lengthy period of time before potentially affecting other locations in the Caribbean. Either way, this will be a slow-moving system.
All interests in the western Caribbean Islands and central America should monitor the progress of this system closely.
If another tropical storm forms this calendar year, it's name would be "Otto." Otherwise, we'll have to wait for "Arlene" next spring or summer.

A Worrisome Threat: Rainfall Flooding

Given the slow movement, this area of disturbed weather may wring out torrential rain from Central America to parts of Hispañola and Jamaica.
This may particularly be the case as moisture interacts with a sluggish frontal boundary from the western Atlantic Ocean southward into the Caribbean Sea late in the week.
All eyes will be on Haiti for this heavy rain potential, still struggling after Hurricane Matthew, and after a renewed round of flooding last week.
It is becoming less likely, though, that torrential rainfall will reach Hispañola, but the likelihood of 1-3 inches of rainfall remains.

November Named Storms Aren't Unusual in the Atlantic Basin

As waters cool farther north and east, and upper-level winds strengthen, the area where tropical cyclones can form shrinks.
In November, tropical cyclones typically form where the waters are warmest. This typically is in the western Caribbean Sea, where you see two clusters of storm origins below.

Tropical cyclone origin points for November.

Although the Gulf of Mexico and Bay of Campeche stay relatively warm, the jet stream shifts south, bringing with it cold fronts. The environment tends to become increasingly hostile due to stronger wind shear, dry air intrusions and cooler air.
Occasionally, tropical systems can spin off of one of these decaying fronts in the western Atlantic or Caribbean.

November tropical storm and hurricane impacts in the United States

According to NOAA's best track database, there have been 36 Atlantic tropical cyclones of at least tropical storm strength in November from 1950 through 2015. Twenty of those became hurricanes.
Just eight years ago, Hurricane Paloma reached Category-4 intensity, the second-strongest November hurricane of record, damaging or destroying nearly every building on Cayman Brac, according to the National Hurricane Center's final report. "Paloma" was retired from the Atlantic hurricane name list following this event.
(MORE: Retired Atlantic Hurricane Names)
In the period of record from 1851 to 2014, no tropical storm or hurricane has impacted the western Gulf Coast from Texas to Mississippi.
To the southeast, systems that do develop across the Caribbean Sea can gain some organization, as the area has supported such late-season hurricanes as Kate in 1985 and Michelle in 2001. The former became the latest landfalling hurricane in Florida’s history on Nov. 21.
Since 1851, Florida has been impacted by eight tropical storms and hurricanes in November. The only other states with more than one November impact were also in the Southeast: Alabama, Georgia and North Carolina.
Typically, November tropical systems follow upper-level flow and cold fronts northeastward into the Atlantic Ocean.

Typical Tropical Tracks for November.

In 2015, Hurricane Kate was an early-November oddity, forming from a tropical wave that first soaked the Lesser Antilles, then becoming the farthest north hurricane so late in the season on record north of Bermuda.
By the way, Atlantic Basin tropical storms even form in December, and January, on rare occasions.
Check back with us at weather.com for the latest on this potential late-season tropical system.

MORE: Late Season Hurricanes