Tuesday, August 8, 2017

Franklin Strengthening in the Western Caribbean; Tropical Storm to Strike the Yucatan with Heavy Rain, Gusty Conditions

Jonathan Belles
Published: August 7,2017

August is historically the beginning of the annual ramp up of hurricane season in the Atlantic, and right on cue, Tropical Storm Franklin has formed in the western Caribbean.
Franklin is expected to be a rainmaker, but it has the potential to quickly be a wind producer too.
A second area of lower pressures is being watched in the central Atlantic.
Here is our latest thinking:
(MORE: Hurricane Central)

Mexican Rainmaker: Tropical Storm Franklin

Here's the latest from the National Hurricane Center:
  • Tropical Storm Franklin is located about 325 miles east-southeast of the Chetumal, Mexico.
  • The system is forecast to strengthen over the next couple of days.
  • Heavy rain is expected to be the main threat, but gusty winds and increased seas are also likely. 
  • Franklin should stay well south of the Mexico/Texas border. 
  • Tropical storm warnings have been issued for Mexico from Chetumal northward and around the Yucatan Peninsula to Campeche.

Current Storm Status
Shower and thunderstorm activity has continued to organize in association with Franklin as it moves through the western Caribbean Sea. A backward "C" shape has developed on satellite as of Monday morning, indicating that the system is organizing and is intensifying.
The environment around Franklin is improving and it is likely that the system will become a robust tropical storm before reaching the Yucatan peninsula. There is an outside shot that Franklin could become a hurricane prior to landfall.
The hurricane hunters will fly a reconnaissance mission into Franklin on Monday, if necessary, to figure out how strong winds have gotten.
(MORE: Final 2017 Atlantic Hurricane Forecast Update: More Active Season Predicted)
In the near-term, Tropical Storm Franklin will bring locally heavy rain and gusty winds to the Cayman Islands and Honduras into early Monday. Belize and the eastern Mexican coasts should expect rainfall to begin midday Monday with rainfall spreading inland through the day.
The northwestern Caribbean and the southwestern Gulf of Mexico will likely 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.
Tropical storm warnings have been issued for Mexico's Yucatan Peninsula. Tropical storm conditions are also possible in Belize from Belize City northward to the Mexican border and along Mexico's Gulf of Mexico coast from south of Campeche to Sabancuy.
Winds of 40 mph or greater may begin in the Yucatan peninsula as soon as Monday afternoon.

Current Tropical Storm Watches and Warnings
A tropical storm warning means that winds in excess of 40 mph are expected within 36 hours and that preparations for the storm should be rushed to completion.
A tropical storm watch means that winds in excess of 40 mph are possible over the next 48 hours.
Residents of the Yucatan Peninsula can expect 3 to 6 inches of rain with locally higher amounts. The northeastern coast of Mexico will likely see rainfall amounts in excess of 3 inches through Thursday.

Forecast Rainfall
In addition to the heavy rain, seas will also increase to choppy conditions north and east of the tropical storm's center. Waves in excess of 10 feet could reach the eastern Yucatan coast, including Cozumel and Cancun, by mid to late day Tuesday. Northeastern Mexico will see seas increase during the middle of the week to more than 12 feet.
(MORE: Water is a Tropical Storm's Deadliest Threat)
Seas will increase in southern Texas on Wednesday and Thursday. The threat of rip currents will also increase in southern Texas and northern Mexico.

Projected Path and Intensity
When this tropical storm or potential hurricane reaches the southwest Gulf of Mexico (Bay of Campeche), it could strengthen significantly once it reaches the warm waters there according to a few computer models.
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.

Caribbean System Steering
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 midway between Africa and the Lesser Antilles as Invest 99L.
As of Sunday evening, the NHC says Invest 99L has a low 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 somewhat conducive to the formation of a tropical depression or tropical storm. 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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