Influence

Hurricanes stand along, but their environment can have big impacts on a storm.

Jump To:

General Factors

How is a Hurricane affected by...

Wind Shear

Water Temperature

Other Weather Systems

Hurricanes Meet

Mountains

Atmospheric Dust

Movement Speed

ENSO State (El Nino. La Nina, Neutral)

General Factors:

Multiple factors affect a Hurricane. These can include wind shear, water temperature, other nearby weather systems (including other hurricanes), mountainous terrain, High Pressure, land mass, dust in the atmosphere, dry air, how fast the cyclone is traveling, storm structure, etc. There are many other variables, weather system interactions, timing, distances, etc. that play a role in tropical cyclone formation. Not only is weather what’s happening at ground level around you, but it involves the 3d aspect reaching from ground level to tens of thousands of feet up.

How does Wind Shear factor in?

Wind Shear occurs when wind at different heights in the atmosphere travels in different directions or speeds. For example: the wind at ground level may be a gentle breeze blowing from West to East, while higher up where airplanes travel, around 30,000ft (9,144m), the wind may be blowing strong from North to South. This phenomenon can sometimes be made visible by the movement of clouds on satellite imagery moving atop each other in different directions. While wind shear can help strengthen thunderstorms in some situations, when it comes to Hurricanes wind shear typically hurts the storm system. Hurricanes prefer light wind shear. High wind shear can disrupt a storm's structure, push in dry air, keep an eye from forming or closing off, or substantially weakening it. In some cases all the storms can literally be blown off leaving just the lower level circulation a harmless swirl of clouds with no rain or storms. The more healthy and more organized a hurricane is, the better it can fight wind shear. A storm with a closed eye (eyewall completely encircles the eye) can protect its core compared to a storm without a closed eye that can allow for the disruption of its remaining structure, allow dry air to enter, etc.

How do Water Temperatures affect Hurricanes?

Water temperature is just one of the many ingredients needed for tropical cyclogenesis and intensification, but it is a main one. Every single degree can matter. A temperature range of just 5 degrees can be the difference in supporting a Cat1 and a Cat3 or higher Hurricane (again, there are many factors involved). The sea surface temperature is not the only factor, but also the depth of that heat content. As a tropical cyclone travels, rough seas stir up waters underneath the storm system. This churn can bring up cooler waters from further below the water surface. The speed and track of a storm over this water can influence the storm strength. Should a tropical cyclone sit nearly stationary or travel too slowly, cooler waters can be brought to the surface by rough seas and weaken or limit the storm from intensifying further. A storm passing through a region of water can temporarily reduce the available heat content for the next storm system as well. Near land heavy rain runoff into the Ocean or Gulf of Mexico, for example, can cool waters as well. Along the US Eastern seaboard sits the Gulf Stream current, a warm water transport coming from around the tip of Florida, up off the Carolina coast. Storms near land hitting this current can receive a sudden burst of energy through the warm water heat energy it gives off.

How do Hurricanes react to other Weather Systems?

Hurricanes are basically self contained weather systems. They can be sloppy weak systems to powerful category 5 behemoths. But they are steered through the atmosphere by other weather systems around them. High Pressure (the big blue ‘H’ on weather maps) has a regional clockwise rotation force in the North Atlantic, and along with the trade winds, causes storms to move East to West as travel South of the High, then turn up North along the Western side of High Pressure following that clockwise flow. The stronger the High Pressure the harder it is for the Hurricane to make that North turn. The ‘Bermuda High’ in the Atlantic generally sits near Bermuda helping steer Atlantic storms towards Florida and the Gulf of Mexico or can help steer them up along or near the US East coast and eventually turn them out to sea. Strong Cold Fronts can also push or block Hurricanes. Weather systems could cause a tropical cyclone to stall allowing for intense rainfall and flooding (like Harvey(2017) in Texas and Louisiana, US). Cyclone closer to a High Pressure can cause pressure gradient resulting in strong winds between the two systems. Tropical moisture trail can be linked to a Hurricane feeding it moisture from afar. A Low Pressure developing on the tail end of a Cold Front can eventually become a Tropical Cyclone (sometime seen over the Gulf of Mexico).

What happens when two Hurricanes meet?

On occasion two tropical cyclones will be close enough to interact. This varies by storm structure, size, and other nearby weather conditions but in general a few hundred miles can be close enough for some form of interaction. Two Hurricanes meeting do not create a larger hurricane. But one storm can absorb or destroy the other, both can hurt each other, and sometimes they do a little dance called the Fujiwhara effect where they spin around each other (more common in the Pacific).

What is the effect of Mountains in a Hurricane?

Mountains play an important role with Tropical Cyclones. Mountains can ring out additional heavy rainfall totals as storms rise to cross over mountainous areas resulting in floods and mudslides. They can also substantially weaken tropical systems like tripping someone running. Hispaniola in the Caribbean is an example of this and sometimes referred to as the ‘Hurricane Shredder’ weakening storms that cross directly over the higher terrain of the island. High terrain can, on occasion, actually help a system form by redirecting winds that in just the right circumstances to help a storm form a more complete eyewall.

Atmospheric Dust change things?

Dry dust filled air can affect tropical cyclones. In the Atlantic this is most prevalent with ‘SAL’, Saharan Air Layer where dusty dry air is transported from the Saharan Desert of Northern Africa all the way across the Atlantic through the Caribbean and sometimes up into the US and portions of South America. Well developed tropical systems with an eyewall surrounding the inner core, or eye, can sometimes fight off this dry dust filled air while weaker systems can ingest and weaken further or even fall apart.

Does the speed at which a Hurricane moves matter?

The speed at which a tropical cyclone is traveling can play a role in the formation and strength of a storm. If it is moving too fast then the layers of a tropical system (from water surface to cloud top) can’t align more vertically causing the storm to become weaker or miss out on strengthening. It’s like imparting its own generated wind shear upon itself, hurting the system. If a storm moves too slowly, it may churn up cooler waters further below the Ocean surface and cause the system to weaken as it loses the heat energy from warmer surface waters.

How does ENSO state play a role?

The ENSO state (El Nino Southern Oscillation) consists of either El Nino (warmer), La Nina (cooler) or Neutral (in between) phases of the equatorial Pacific water temperatures. The water temperature in this region affects the weather and climate across the entire globe. For tropical cyclones of the Atlantic, Central and Eastern Pacific, during El Nino years the Atlantic typically sees less activity (due to increased wind shear) and the Central and Eastern Pacific basins see above average activity. During La Nina years the opposite occurs with above average activity in the Atlantic and below average seasons in the Central and Eastern Pacific. Neutral years tend to also be active seasons for the Atlantic, although not as much as La Nina seasons.