What is the Relevance of the "Main Development Region" to Hurricane Activity? (credit: NOAA)
DISCUSSION: As a follow-up to the previous article regarding the importance of the Loop Current on Tropical Atlantic hurricane activity and corresponding intensity potential, it makes sense to also discuss the importance of the region of the Tropical Atlantic basin which is designated at the "Main Development Region." The "Main Development Region" (MDR) is the region of the Tropical Atlantic Ocean basin which extends from approximately just offshore from the west coast of Africa and westward towards the western-most sections of the Caribbean Sea. This vast amount of tropical ocean is a region which is often more closely monitored for potential tropical system development during the course of a given Atlantic hurricane season. It is worth noting that despite not being discussed here, there also is a particularly favorable MDR for the Tropical Eastern Pacific Ocean basin as well. However, for the purposes of this discussion, the focus will remain on the MDR across the Tropical Atlantic basin.
In re-focusing into our topic of interest being the Tropical Atlantic basin's MDR, it is important to establish the fact that during any given year, the Tropical Atlantic's MDR often will behave slightly different depending upon the exact oceanic and atmospheric conditions which are in place throughout the course of a given Tropical Atlantic hurricane season. Hence, no one season is ever perfectly identical to another regardless of how similar the evolution of storm formation and given storm intensity may be from one season to another. Thus, when trying to say that one year is reminding oneself of another year based on some given factor, you are more than likely not correct since there are many unique surface, low-level, mid-level, and upper-level atmospheric as well as corresponding oceanic factors which make every single global tropical cyclone season different from the next.
A graphic which perfectly illustrates this point is the one which is attached above (courtesy of the National Oceanic and Atmospheric Administration's Climate Prediction Center office). This graphic attached above shows how and why during the course of the current 2018 Tropical Atlantic hurricane season there has been relatively to no tropical activity for a good portion of what is considered to be the more active parts of a typical year. This lack of tropical storm activity has been largely due to the persistent presence of stronger vertical wind shear as well as a persistent presence of pronounced Saharan Dust across a substantial percentage of the Tropical Atlantic's "Main Development Region" during the large majority of the 2018 Atlantic hurricane season up to this point. Thus, as shown in the above graphic, the combination of unfavorable wind patterns along with the cooler sea-surface temperatures and the persistent Saharan Dust plume progression has predominantly led to a mostly quiet Tropical Atlantic basin here in 2018 for the most part. It is imperative to acknowledge the fact that this could change soon as large-scale conditions are anticipated to improve somewhat in the days and weeks ahead here in September and into early October. So, as always, be sure to stay tuned to our global team at the Global Weather and Climate Center for the very latest!
To learn more about this topic and this topic in reference to the 2018 Tropical Atlantic hurricane season, feel free to click here.
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© 2018 Meteorologist Jordan Rabinowitz
How is the Loop Current Tied to Atlantic Hurricane Intensity? (credit: Meteorologist Jordan Rabinowitz)
DISCUSSION: During the course of a given Tropical Atlantic hurricane season, there are a number of different factors (i.e., both ocean-based and atmosphere-based) which meteorologists will closely monitor. This is due to the fact that with even slight changes in the state of many of these different environmental conditions, there can often be quite substantial changes in the propensity for tropical cyclones to form and/or intensity while moving across different parts of the Tropical Atlantic as just one oceanic basin which will be used as a singular example here. As shown in the graphic attached above (courtesy of the University Center for Atmospheric and the National Oceanic and Atmospheric Administration), you can see a specific oceanic current being depicted here. This ocean current which is known as the Loop Current is effectively a northward extension of the Caribbean Current and the current which later transitions into what are known as the Straits of Florida and eventually becoming the Gulf Stream.
However, across the central and eastern portions of the Gulf of Mexico, the Loop Current will often have one or more "Loop eddies" break away from the main Loop Current just to the east. "Loop eddies" refer to much smaller rotating/pivoting ocean sub-current which allow more isolated areas of warmer upper-ocean water to meander a relatively short distance away from the main Loop Current which will most often gradually progress to the east with time. Due to this factor, when developing tropical storms, intensifying hurricanes, or even mature hurricanes pass over either the Loop Current and/or "Loop eddies", they are quite often given an intensity boost or size boost. This is a result of a given tropical cyclone benefiting from the substantially warmer sea-surface temperatures helping to provide additional fuel for a blossoming tropical storm. Hence, whenever there is a tropical cyclone threat during the late Summer to early Fall time-frame in the vicinity of the Gulf of Mexico, there are often heightened concerns when it comes to nearby tropical storms with the looming presence of the Loop Current.
To learn more about this interesting tropical subject matter courtesy of the National Centers for Coastal Ocean Science, feel free to click here!
To learn more about other high-impact weather stories and/or topics from across the Atlantic Ocean and Caribbean Sea, be sure to click here!
© 2018 Meteorologist Jordan Rabinowitz