Tropics Come Alive: Tracking the Cape Verde Train

Its amazing how much a week changes everything in the tropics. Last week this time, we were looking at pretty tranquil conditions across the Atlantic basin, but tonight, the tropics are definitely alive as I'm tracking three systems out across the Atlantic: Hurricane Danielle, Tropical Storm Earl, and Invest 97L. It definitely appears that Cape Verde season has finally come and that the heart of the hurricane season has begun.

Hurricane Danielle

Figure 2 - Latest Hurricane Danielle Satellite

According to the latest information from the NHC at 11PM EST, Hurricane Danielle continues to remain a strong Category 2 storm packing winds around 110 mph with minimum central pressure around 965mb. In the past few hours, Danielle has become better organized and stronger as the eyewall has contracted and become more symmetrical while convection continues to deepen in the eyewall. In my opinion, Danielle should be a major hurricane right now given current satellite presentation and the latest trends in organization. During the day, dry air had gotten entrained into the storm from the southeast, but the storm has quickly cycled out the dry air and restrengthened. 

As for the future, it seems pretty clear. Danielle has now entered a weakness in the subtropical ridge that had been driving the storm across the Atlantic and should begin to move northerly in the next 12 to 24 hours as a deep trough continues to cut across the Northern Atlantic and pull the storm out to sea. It should become a major hurricane tomorrow morning and should remain so for another 24 hours before it encounters pretty hostile upper level winds from the trough. The only impacts to any land areas will be some pretty strong swells hitting Bermuda and the shores the Eastern United States over the next 3 to 5 days before the system gets pulled well out to sea and towards Europe down the road as an extra-tropical storm.

Tropical Storm Earl

Figure 3 - Latest Tropical Storm Earl Satellite

According to the latest information from the NHC at 11 PM EST, Tropical Storm Earl continues to maintain 45 mph and a minimum central pressure around 1003mb. Satellite this evening shows two main convective clusters in association with this storm with a pretty broad circulation. In doing some analysis tonight, I believe the circulation center is located between these two convective clusters. During the past couple days since it became a tropical cyclone, Earl has been and continues to battle dry air surrounding the storm. Water vapor imagery shows that the storm has begun to moisten the atmosphere around it, so this may not be a problem for much longer. As it stands right now, Tropical Storm Earl appears to be somewhat disorganized tonight as it struggles against dry air and convection doesn't exhibit the classic low level spiral pattern typical of a strengthening tropical storm.

The forecast for Earl is a bit more tricky than with Danielle. Over the next 3 days or so, Earl will continue to ride the periphery of the subtropical ridge that steered Danielle across the Central Atlantic. By early next week, it should approach the same area Danielle encountered the weakness in the ridge. The big question remains whether or not the weakness will still exist when Earl arrives on the scene. This will depend on how strong Danielle is at the time and how quickly Danielle recurves. 

If Danielle leaves the picture quickly, this could allow the subtropical ridge to build back in over Tropical Storm Earl and force it to move WNW where it becomes even more uncertain. If Danielle is strong and moves slower, Earl will feel the "pull" from Danielle and will follow the so-called leader.

For now it remains too uncertain to be sure and the latest forecast track from the NHC reflects this.



Invest 97L

Yet another strong tropical wave moved off the African coast yesterday and has already begun organizing, much like Danielle and Earl did. A recent ASCAT pass showed a defined low level circulation in association with the system, but displaced to the east of the convection. Recent microwave imagery shows pretty decent spiral banding. The NHC currently gives the system a high chance (60%) of becoming a tropical depression in the next couple days. I believe the chances are higher considering it has a well defined low level circulation and spiral banding is becoming established.

Right now its too soon to tell what the future holds for this system as its just entered the picture and computer models are very spread out at this time.