Lots of maybes in the Atlantic, but no immediate development contenders

No tropical threats expected for the US in the week ahead

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The theme of the past few weeks continues across the Atlantic with several systems struggling to gain footing as dry and sinking air quickly squashes organized storminess.

The welcome news means we could escape the first full week of September – a typically busy week of the hurricane season – without any organized tropical systems in the Atlantic, the first time that’s happened in 30 years.

NHC lowers development odds for Caribbean cruiser

The disturbance we’ve been following since last Tuesday that’s now moving quickly through the central Caribbean again shed its associated storminess overnight. Models remain generally tepid on development as it plows westward, but there’s a narrow window as it nears Central America where it could try to organize. In general, the slowing of trade winds in the western Caribbean supports more thunderstorm growth – a process known as convergence, whereby winds pile up – and wind shear should stay fairly light and conducive. But given model trends and past struggles, don’t expect this to develop quickly.

Regardless, the upshot will be heavy rains and a multi-day flood threat spreading into portions of Belize, Guatemala, northern Honduras, and southern Mexico this weekend into early next week.

Low pressure tracks from the European forecast model ensemble system through Sunday morning. Most scenarios depict a weak system moving inland across Central America this weekend. Credit: Weathernerds.org.

There’s a small chance of redevelopment in the southern Gulf of Mexico next week, but for now those odds remain low. The more likely scenario is movement deeper into Mexico or the toward the eastern Pacific for next week.

The system poses no threat to South Florida.

Deep Atlantic perks up for late next week

The Hurricane Center has tagged two disturbances today out in the wide open Atlantic. Although we could see some slow development with either system into next week, neither will be headed toward any land areas and computer models show little in the way of robust development.

That said, our primary global models do indicate the possibility of the deep Atlantic perking up by the latter part of next week into next weekend (the weekend of September 14th). They don’t agree yet on where development could occur, but the general trend shows a noticeable reduction in wind shear and a drop off in the dry conditions plaguing the eastern Atlantic.

Wind shear departure from average forecast for middle to late September (September 13-18) from the European forecast model ensemble system (left) and the American GFS forecast model ensemble system (right). Both models show a noticeable reduction in wind shear by around the middle part of the month. Credit: TropicalTidbits.com.

This is also broadly consistent with the return of the rising branch of the Madden-Julian Oscillation, or MJO, which could bring more favorable conditions back into the Atlantic writ-large for the end of the month.

Areas of rising (blue/cool colors) and sinking (red/warm colors) air straddling the equator (between 15°N and 15°S) by global longitude (x-axis) from early August (top of the chart) through October 5th (bottom of the chart). The time vs. longitude chart is known as a Hovmoller diagram and shows the global progression of weather features. The forecast charts indicates the sinking air plaguing the Atlantic will be replaced by the rising air branch (part of the Madden-Julian Oscillation or MJO) by late September (favored zone shown on the plot). The last time the Atlantic was in this favored zone was back in July. Credit: ECMWF.

We’ll have more to say on this change of pace soon.


About the Author
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Michael Lowry is Local 10's Hurricane Specialist and Storm Surge Expert.

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