This is a quick tropical-storm update for the group as activity in the Atlantic Ocean heats up this week.

You might have noticed named storm Danny is no longer a threat and has been discontinued by the National Hurricane Center (NHC). Instead, it is now an open tropical wave as it approaches the southern shores of Hispaniola. However, there is a very slight chance that this open tropical wave could become better organized once again as it approaches the southern Gulf of Mexico this weekend, but this is a long shot at this point in time.

The new concern is a tropical wave that emerged off the West Coast of Africa last week. This tropic wave is currently has a 90% chance of development according the NHC and should be named storm Erika by tomorrow. The low pressure system is located about 1,250 miles east of the southern Lesser Antilles.

Why should soon to be named Erika be more of a concern than Danny?

First, this tropical wave is at a higher latitude. Danny started out at a latitude of 10.6 degrees north while this new tropical wave is at a latitude of 14.6 degrees north, which is a better location for intensification. Further, climatology indicates that this latitude is more likely to create a U.S. threating storm.

Secondly, Danny also was surrounded by dry, dusty air which limited its development in size and intensity. This new tropical wave will not have to fight as much of this dry, dusty air.

DannyDust

Dust and dry air as Danny was forming last week.

Dust824

Dust and dry air as TD5 is trying to organize.

Notice how much less dust and dry air is around this tropical wave versus the dust and dry air around Danny last week.

Thirdly, an upper-level trough has brought a taste of fall to much of the East Coast. As the trough slowly lifts out of the East Coast this week, upper-level winds will be much more conductive to less shear in the Atlantic Ocean.

 

0_5dayHeights

ECMWF 5 day anomaly chart which suggests cooler temperatures lower air pressure (blue area) along the East Coast of the U.S.

Day5

ECMWF next weeks (Day 5 – 10) anomaly chart which suggests warmer temperatures and higher air pressure (orange area) along the east coast of the U.S.

As you can see, next week’s forecasted weather pattern is much different than this week’s. Although there is some uncertainty in the track and intensity with any named storm forecast. Overall, next week’s weather should allow what will be Erika to track much further northwest ward toward the Bahamas as a hurricane. In fact, Erika could be a major hurricane by the time it reaches the Bahamas on August 30th given the warm sea surface temperatures near the islands. It is a bit early to determine how much of a U.S. landfalling threat Erika will be, but most storms near the Bahamas need to be watched, and this will be the case the first week of September.

HWRFERIKA_824

0z Aug 24 HWRF model Run Erika

The HWRF model, which did a great job with the intensification of Danny late last week, This model now provides a view of my general thinking as Erika tracks towards the Bahamas.
HWRF modeled 126 hour forecasted wind speeds of soon to be Erika.

Named Storm Fred could also develop behind Erika later this week, but let’s worry about Erika first.

Updates as needed or ask if you have questions.