Sunday, August 6, 2017

Caribbean System Could Develop Into a Tropical Depression or Storm; Watching Atlantic Disturbance

Chris Dolce
Published: August 6,2017

August is historically the beginning of the annual ramp up of hurricane season in the Atlantic, and right on cue, there are a couple of areas to watch in the Atlantic basin during the new week ahead.
A system currently passing through the Caribbean has the best odds for development early this week and is likely to impact land. Here's what to expect.
(MORE: Hurricane Central)

Caribbean Area to Watch: Invest 90L

Shower and thunderstorm activity has continued to organized in association with a strong tropical wave that is moving through the western Caribbean Sea.
The NHC has dubbed this tropical wave Invest 90L. This is a naming convention used to identify features that could form into a tropical depression or tropical storm.
(MORE: What is an Invest?)
In the near-term, Invest 90L will bring locally heavy rain and gusty winds to Jamaica and the Cayman Islands on Sunday.
Some forecast guidance suggests the tropical wave may contribute to the development of low pressure in the northwest Caribbean or the southwest Gulf of Mexico (Bay of Campeche) early this week. As a result, the NHC has given this system a high chance of development into a tropical depression or tropical storm during the next five days as it moves to the west-northwest.
The next storm name in the Atlantic is Franklin.

Current Satellite
The hurricane hunters will fly a reconnaissance mission into Invest 90L on Monday, if necessary. It is possible that tropical storm watches or warnings may be issued on Sunday or Monday for portions of Mexico, Belize or Honduras if this system becomes better organized.
Even without development, the northwestern Caribbean and the southwestern Gulf of Mexico could see an increase in stormy weather early this week, which may result in locally heavy rainfall and flooding for Mexico's Yucatan Peninsula and Central America.
Should this potential future tropical depression or tropical storm reach the southwest Gulf of Mexico (Bay of Campeche), it could strengthen significantly.
The vast majority of forecast guidance suggests that high pressure in the southern U.S. should remain strong enough that any system that does develop will likely push into northeast Mexico and not directly affect the U.S. That said, residents of the western Gulf Coast, particularly south Texas, should continue to check back for updates to this forecast as it remains several days away.

Atlantic Area to Watch: Invest 99L

In addition to the Caribbean system, there is another region farther away in the Atlantic that's being monitored for the development of a tropical depression or tropical storm. The NHC has designated this area of disturbed weather in the central Atlantic between Africa and the Lesser Antilles as Invest 99L.
As of Sunday morning, the NHC says Invest 99L has a medium chance of developing into a tropical depression during the week ahead.

Atlantic Area to Watch
Invest 99L is forecast to move west or west-northwest along the southern periphery of high pressure during the next five days toward the central Atlantic.
The NHC says atmospheric conditions are conducive to the formation of a tropical depression or tropical storm during the next two to three days. After that time, conditions will be less hospitable for tropical cyclone development.
By the middle of this week, Invest 99L could be near the Lesser Antilles (eastern Caribbean) where it may lead to an uptick in locally heavy rain and gusty winds.
It's far too early to know where this potential tropical depression or tropical storm may head beyond that point later this week or next weekend, assuming it does develop.
There is plenty of time to monitor its progress, so check back for updates.
We've now entered the portion of hurricane season when every potential system must be watched closely for development and potential impacts to land. About 80 percent of all hurricanes in the Atlantic have developed from August through October.
(MORE: Most Notorious Part of Hurricane Season is Here)
It has been almost five years since a hurricane made landfall in the United States during August. The last one was Hurricane Isaac, which struck Louisiana on Aug. 28, 2012.

Five Named Storms So Far, But It Really Hasn't Been That Active

As mentioned before, the Atlantic has already seen five tropical storms through Aug. 2. On average, the fifth named storm does not arrive until Aug. 31, based on the 1966-2009 average.
While we are far ahead of the average pace for named storms, that doesn't tell the whole story.
2017 named storm tracks through Aug. 2.
A better way to measure the pace of a hurricane season is to use the ACE (Accumulated Cyclone Energy) index, which is calculated by adding each tropical storm or hurricane's wind speed through its life cycle.
Long-lived, intense hurricanes have a high ACE index, while short-lived, weak tropical storms have a low value. The ACE of a season is the sum of the ACE for each storm and takes into account the number, strength and duration of all tropical storms and hurricanes in the season. A season's ACE value doesn't necessarily reflect the severity of impacts to land in a given season.
Since all five named storms were weak and didn't last long, this season's ACE index is fairly low so far. The ACE index through Aug. 2 was the lowest for that date since 2009, according to Dr. Phil Klotzbach, a tropical scientist at Colorado State University.
Klotzbach added that the combined ACE for the first five named storms this season is the lowest for any first five storms on record in a given year.
MORE: Weirdest Hurricane and Tropical Storm Tracks

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