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  • Writer's pictureBryan Norcross

Something to watch at the end of the week

NOTE: I’m experimenting with ChatGPT 4.0. The first part of the post below was written by me with GPT checking the spelling, etc. ChatGPT wrote the Key Points Expanded section, though I had to tune up its part for clarity and to remove some fancy words that GPT seemed to like. See what you think.

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The tropics are on pause for now. Saharan dust is dominating the tropical Atlantic. Even though robust tropical disturbances are moving off Africa, they can't develop as they move west. Dust normally peaks in late June and July, so this is not unexpected. So far this year, there has been somewhat less dust than normal, but now the density of the dust is about average.



The National Hurricane Center is identifying one of the African disturbances that we'll have to watch at the end of the week when it reaches the western Caribbean. The atmospheric pattern is forecast to be conducive for development at that time, and the system will have moved past the dust.



The Hurricane Center is giving the disturbance a low chance of developing at this point. The timeframe we're talking about is over next weekend. A blocking high-pressure system is forecast to set up across the southern US. This should keep any development well to the south.


Tropical Storm Alberto and the two disturbances that couldn't quite get organized are the kinds of systems we expect to see in June. If a disturbance that originated over Africa is able to develop, it most often happens after it passes the Caribbean Islands.


For now, there is nothing to look at, but we will keep an eye on it this week. Long-range computer forecast models indicate that the overall atmospheric pattern might be more conducive for development around the end of the month or the beginning of July. We'll see.


Key Points Expanded


What is Saharan Dust and How Does it Affect Tropical Weather?

Saharan dust consists of tiny particles from the Sahara Desert that are lifted into the atmosphere by strong winds. This dust can travel thousands of miles across the Atlantic, reaching as far as the Americas. When Saharan dust is present in the atmosphere, it creates a dry and stable layer, making it difficult for thunderstorms to organize and grow into tropical storms or hurricanes. This phenomenon is called the Saharan Air Layer (SAL).


Why Is There Less Dust Than Normal This Year?

This year, there has been somewhat less Saharan dust than usual. This fluctuation can be attributed to various atmospheric conditions and changes in wind patterns. Factors such as the strength and position of the large high-pressure system that dominates the Atlantic, as well as the temperature and humidity levels over the Sahara, can influence the amount of dust lifted into the atmosphere. Currently, the dust levels have returned to about average.


How Do Tropical Disturbances Develop?

Tropical disturbances, often starting as clusters of thunderstorms, can develop into more organized systems like tropical depressions, storms, or hurricanes under the right conditions. Key factors for development include warm ocean-water temperatures, conducive upper winds, and high humidity in the middle of the atmosphere. When these conditions are met, the disturbances can consolidate and strengthen as they move over the ocean.


Long-Range Predictions from the Climate Prediction Center

The Climate Prediction Center (CPC) formulates long-range predictions using a combination of global climate models and observational data. These models incorporate various atmospheric and oceanic variables, such as ocean-water temperatures, wind patterns, and moisture levels. By running atmospheric simulations multiple times to imagine different scenarios, the CPC can provide probabilistic forecasts for tropical weather development. Historical data and current observations are also used to refine these predictions. The result tells us where and when to look for potential tropical activity up to 3 weeks in advance.

 

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