Monday, August 17, 2015

The Tropics are waking up

The Tropics in the Atlantic are waking up. NHC is keeping their eyes on three features.
  1. There is an area of low pressure off the West Coast of Africa
  2. A Tropical Wave in the middle of the ocean
  3. Tropical Wave over Eastern Cuba/Western Haiti.
 Lets eliminate the middle wave as it appears it may fall apart over the next 24-48 hours.

We begin with the area of low pressure in the Far Eastern Atlantic.
As of Monday night this is what NHC was saying:

Showers and thunderstorms associated with an area of low pressure
located several hundred miles southwest of the Cape Verde Islands
are gradually becoming better organized.  Environmental conditions
appear conducive for additional development of this system, and a
tropical depression will likely form within the next few days while
the system moves west-northwestward at 10 to 15 mph.
* Formation chance through 48 hours...medium...60 percent
* Formation chance through 5 days...high...80 percent

On the Satellite loop, you can see the dark blue, orange and red areas. This indicates where the strongest storms can be found. Keep an eye on this over the next few days as it will be key as to how quickly it may turn into a possible named system.

Because this area is getting better organized, NHC has named it Invest 96L.  Invest because they want to INVESTigate it further. Once named an Invest, they can dedicate more time and resources. 96 for the 6th system to be called an Invest (they always start with 90). And L for the AtLantic Basin.

Where to watch?
If it were to develop, it would do so in the area highlighted in red.

It would still be East of the Lesser Antilles. If it stays on this track it would drop beneficial rain over the islands.

From Cuba, through Jamaica, Hispaniola, and the Lesser Antilles they are all in the midst of a severe drought, so any rain is welcome.

What's steering it?

High pressure will remain firm in the Atlantic throughout the week.

Most of the models agree the low will continue to move west at around 10 - 15 mph.

At this speed, even if it does develop it should still be hundreds of miles away from the windward islands by the weekend.

What does it have working for it?
Even though the Atlantic waters in the Eastern Atlantic are not that warm, there is sufficient heat for it to grow.

The minimum temp required for cyclogenesis is 80°.

You can see by our graphic that waters off the African coast are just above that threshold.

Hot water is like jet fuel for these tropical engines allowing them the chance to get stronger.

What's working against it?

  • There is plenty of Saharan Dust just north of the low. This could inhibit any organization in the days ahead. 
  • El Niño in the Pacific Ocean is causing strong upper level winds over the Atlantic that could keep it in check. There is plenty of time to watch this low

Tropical Wave over Hispaniola:
Tropical waves are very difficult to forecast. They can grow fast or fall apart rather quickly.

Right now there's a wave over Hispaniola.  There's also an Upper Low just ahead of it.

If both of these disturbances do not fall apart, they will help to draw some moisture our way and could lead to pockets of rain by Tuesday night and Wednesday.

Our in house model suggests we could see areas with more than 2 inches over 2 days.

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