earth science

Post-tropical cyclone

Post-tropical cyclone is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Post-tropical cyclone rather than just read about it. In short: A post-tropical cyclone is a former tropical cyclone that no longer possesses enough tropical qualities to be considered a tropical cyclone. The word may refer to a former tropical cyclone undergoing extratropical transition or a tropical cyclone degenerating into a remnant low.

Key takeaways

Post-tropical cyclone belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Post-tropical cyclone to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Post-tropical cyclone from memory before moving on to harder problems.

Reference excerpt

A post-tropical cyclone is a former tropical cyclone that no longer possesses enough tropical qualities to be considered a tropical cyclone. The word may refer to a former tropical cyclone undergoing extratropical transition or a tropical cyclone degenerating into a remnant low. A tropical cyclone degenerating into a trough or wave, or having its low level circulation dissipate overland, lacks a cyclonic circulation and is referred as remnants instead of a post-tropical cyclone. However, post-tropical cyclones or remnants can continue producing high winds and heavy rains.

Classification/Other post-tropical cyclones

Classes Two classes of post-tropical cyclones exist

Extratropical cyclone, which is frontal, sometimes still retains winds of hurricane or tropical storm force. Hurricane Paulette (2020) provides a recent example of an extratropical cyclone, in which it no longer has a warm core in higher latitudes when it was over Nova Scotia and all points north in its trajectory. Remnant low, which is non-frontal, has maximum sustained winds of less than 34 knots, and mainly consists of stable stratocumulus with little to no convective activity. These shallow systems may meander for some time before opening into a trough of low pressure, or by being absorbed into an extratropical cyclone.

Other post-tropical cyclones Not all systems fall into the above two classes. According to the guideline, a system without frontal characteristics but with maximum winds above 34 knots may not be designated as a remnant low. It should be merely described as post-tropical. A few examples falling into this grey area are listed below.

Eugene (2011) Michael (2012) Nadine (2012) Humberto (2013) Joaquin (2015) Matthew (2016) Jerry (2019) Paulette (2020) Guambe (2021) Linda (2021) Batsirai (2022) Emnati (2022) Blas (2022) Frank (2022) Howard (2022) Kay (2022) However, there has been an occasion that the United States National Hurricane Center went against that definition and designated Calvin (2011) as a 35-knot remnant low. Also, if a tropical cyclone degenerates into a tropical wave or trough, then it does not qualify as a post-tropical cyclone. It would be referred as the "remnants of (tropical cyclone name)". Météo-France classifies systems in the South-West Indian Ocean undergoing an extratropical transition or losing tropical characteristics as "post-tropical depressions", since the 2012–13 cyclone season. They would be re-classified as extratropical depressions after completing the process.

Formation A post-tropical cyclone is formed when the typical characteristics of a tropical cyclone are replaced with those of extratropical cyclones, otherwise known as extratropical transition. After the initial formation, a post-tropical cyclone has the potential to gain strength and intensity by forming an extratropical storm. If a post-tropical cyclone does become an extratropical storm, it will eventually decay through the process of occlusion.

Impacts The re-intensification of a post-tropical cyclone can cause dangerous conditions in North Atlantic shipping routes with high seas and winds comparable to those of hurricanes.

Origin The terminology was initiated by Meteorologist Peter Bowyer of the Canadian Hurricane Centre in 1998 during Tropical Storm Bonnie. In 2008, the National Hurricane Center used this term for Tropical Storm Laura to address the limitation of the two classes (extratropical/remnant low) mentioned above. The term was later adopted by the National Weather Service on May 15, 2010.

Synonym The Bureau of Meteorology in Australia refers to a former tropical cyclone as an "ex-tropical cyclone". An example is ex-tropical cyclone Oswald.

Illustrations

Worked examples

Example 1 — a first encounter with Post-tropical cyclone

Start with the simplest possible case. Write down what Post-tropical cyclone claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Post-tropical cyclone before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Post-tropical cyclone ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Post-tropical cyclone

In research: Post-tropical cyclone appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Post-tropical cyclone in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Post-tropical cyclone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Meteorological phenomena, Tropical cyclone meteorology, Tropical cyclones, so understanding it makes those chapters shorter.
In everyday life: Look for Post-tropical cyclone outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Post-tropical cyclone in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Post-tropical cyclone means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Post-tropical cyclone out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Post-tropical cyclone in simple terms?

Why does Post-tropical cyclone matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Post-tropical cyclone?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Post-tropical cyclone.