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Tropical Tracker: A busy Eastern Pacific a sign of things to come for the Atlantic?

Dry air, Saharan dust keeping Atlantic tame for now

The Eastern Pacific currently has one tropical depression and two areas with a high likelihood for development.
The Eastern Pacific currently has one tropical depression and two areas with a high likelihood for development.

ORLANDO, Fla. – As we talked about in last week’s edition of the Tropical Tracker, the Atlantic remains relatively unfavorable for tropical development. We do have Tropical Storm Josephine, but that is expected to run into dry air and shear and may dissipate all together. Either way, it appears to be a non-factor for Florida.

Josephine did become the earliest “J” storm on record beating out Jose of 2005. While we continue to outpace the record season of 2005, the accumulated cyclone energy from ’05 remains far and away higher as most of the storms in 2020 to date have been weak and short-lived. ACE is calculated by using the intensity and duration of the storm once it reaches tropical storm status.

The current ACE through Aug. 12 is 23.1, which is well above the average ACE to date of 11. For perspective, the ACE to date in 2005 was a whopping 70.1. Through the “J” storm in ’05 we already had three hurricanes, two of them being major including Category 5 Hurricane Emily.

Current state of the Atlantic:

Even though we have been on a record tear this season, storms, including hurricanes Isaias and Hanna, have had trouble intensifying. That is all because of the wind shear, dry air and dust still present in the Atlantic. Dust normally rules the roost from June through early August and is one of the reasons why tropical activity is typically relatively low in the first couple of months of hurricane season.

This isn't a good sign, however, that we have been able to generate so many storms even when the Atlantic hasn't been that conducive to supporting them. As we move toward the climatological peak of hurricane season, middle of August through early October, things that deter tropical development like the Saharan dust tend to go away.

Dust forecast into early next week. Dust is still helping to keep storms at bay even though it's not as thick as what it was June.   The Saharan dust typically begins to lose its grip in the middle of August.
Dust forecast into early next week. Dust is still helping to keep storms at bay even though it's not as thick as what it was June. The Saharan dust typically begins to lose its grip in the middle of August.

Dust and dry air may try and hang on into next week closer to Africa, but the atmosphere may become more conducive in the Caribbean and Gulf of Mexico. It will be interesting to see how much of the dry air we can hang on to as things look to ramp up over the next week or two. More on that below.

A bad sign of things to come?

After a really quiet start to the Eastern Pacific hurricane season, it’s gone nuts in the past week. As expected, the convectively enhanced phase of the Madden-Julian Oscillation is currently in the Eastern Pacific. Why do we care about that part of the world? Typically when the Eastern Pacific is active, the Atlantic is quiet and vice versa.

The Eastern Pacific currently has one tropical depression and two areas with a high likelihood for development.
The Eastern Pacific currently has one tropical depression and two areas with a high likelihood for development.

When this enhanced phase is over a particular basin, thunderstorm activity increases and the potential for tropical development goes up given other favorable conditions.

MJO's enhanced phase is currently helping to ignite the Eastern Pacific hurricane season.
MJO's enhanced phase is currently helping to ignite the Eastern Pacific hurricane season.

During the next several days to week, rising air associated with the MJO is expected to move over the Gulf of Mexico and Caribbean. The enhanced phase will gradually move across the Atlantic and over Africa through the middle of September. This could cause a significant burst of tropical activity in the Atlantic from the third week of August through at least the middle of September. This could start in the Gulf/Caribbean and then transition to more storms rolling off of Africa. The green on the model below from tropicaltidbits.com shows the progression of where rising motion, needed for thunderstorm activity, is maximized.

Green shaded areas are rising air anomalies. Green shaded areas favor thunderstorm development. Image from tropicaltidbits.com
Green shaded areas are rising air anomalies. Green shaded areas favor thunderstorm development. Image from tropicaltidbits.com
Green shaded areas are rising air anomalies. Green shaded areas favor thunderstorm development. Image from tropicaltidbits.com
Green shaded areas are rising air anomalies. Green shaded areas favor thunderstorm development. Image from tropicaltidbits.com

We are, of course, getting into peak season anyway, but enhanced thunderstorm activity from the MJO combined with peak climatology could create a really nasty period in the tropics through the middle of September. It is impossible to tell at this time if land will be impacted, but it’s something we will obviously be pinpointing closely as we enter the busiest time of the year. Here’s to hoping for the continued fish storms.


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