Beyond Fay

We are moving into the busiest period of tropical development, with the peak of the hurricane season coming on September 10th. So what can we expect over the next few weeks?

First ENSO:

Currently ENSO is slightly positive, which is often correlated to higher levels of wind shear in the tropical Atlantic. However, it is only slightly positive and coming out of a strong negative phase. A lag is often seen in effects reaching the Atlantic, and thus the higher shear is not impacting the Atlantic as you might expect. Also, the long range forecasts predict ENSO to stay near neutral, so no real inhibiting factors should be felt from ENSO on the tropical Atlantic. Its impact on tropical development in the Atlantic will be near zero.

MJO:

Not forecast to be in a conducive (positive) or inhibiting phase (negative). Near neutral conditions means little influence on tropical development.

SST and TCHP:

Sea Surface Temperatures are now supportive of tropical development throughout the tropical Atlantic. The warmest areas are in the western Caribbean, Gulf of Mexico, Bahamas and surrounding waters, and off the South American coastline into the central Atlantic. Tropical Cyclone Heat Potential is greatest in the same locations. Thus, any storm that gets into the northwestern Caribbean into the Gulf of Mexico look to be the most dangerous.

Shear forecasts:

Shear is forecasted to be conducive for development throughout most of the tropical Atlantic development region, especially the Caribbean and into the Gulf over the next week.

Models and Predictions:

The models are continuing to be aggressive with their tropical development. The European and Canadian models develop the current 94L wave just east of the islands in the Caribbean in the next 2-3 days. They bring this system towards Hispaniola north into the Bahamas and stall it in this area. Again, just like with Fay, a trough tries to pull it north (the one currently moving through the mid-western United States) but pulls out before it can completely grab the system. 94L then stalls and begins to move westward as a ridge builds in! Sounds very familiar. If this were to happen, the only hope would be for the teleconnection from Asia working out, which supports a trough digging off the eastern seaboard in about 9-10 days. This would hopefully grab 94L and pull it north.

However, if 94L does not develop quickly, it could continue to track west through the Caribbean and miss both troughs, moving towards Mexico or the Gulf. I think it might be slow to develop, and thus not move as far north, but this should definitely be watched.

Beyond 94L, a second area of interest (95L) is in the central Atlantic. A broad area of circulation is seen and low levels of convection are present. However, no models predict this system to develop and the system is not sitting over the warmest sea surface temperatures. Shear is near 10 knots and will stay near that value for the next few days, likely keeping it from developing before it pulls north and out to sea.

Further waves are forecasted to move off the African coast over the next two weeks, and some of the models forecast one or more to develop. Considering ENSO and and MJO are not going to be inhibiting or helping factors, shear is to be low, and TCHP is decent, I think an average period of tropical development should occur over the next two weeks. This would mean 1-2 tropical systems should develop in this time frame, which is reasonable.