<p>It really depends on how you define storms. For tropical storms, there are some regions where they are not usually a threat. Likewise, for extratropical storms, there are latitudes where such things are not a concern (such as the tropics). The key to understanding the seasonality to such storms is to understand what controls the seasonality of what drives each.</p>
<p><a href="https://en.wikipedia.org/wiki/Convective_instability#:%7E:text=In%20meteorology%2C%20convective%20instability%20or,disturbances%20dampen%20out%20and%20disappear." rel="nofollow noreferrer">Thunderstorms (broadly speaking) rely on a warm air over cooler air</a>. During spring and summer that is more likely to happen. More in the spring, as the land and air near the land responds pretty quickly to the increase in radiation, whereas the air  further away from the land takes some time to adjust. Air that moves over a cool ocean current will tend to be cooler, so less thunderstorms will usually occur where land is downstream of cool water.</p>
<p><a href="https://en.wikipedia.org/wiki/Extratropical_cyclone#:%7E:text=Extratropical%20cyclones%2C%20sometimes%20called%20mid,over%20much%20of%20the%20Earth." rel="nofollow noreferrer">Extratropical cyclones</a> rely on sharp changes in temperature, which is enhanced during winter. That is, the tropics maintain the amount of radiation that they get, while the higher latitudes get less incoming radiation (0 past the Ant/arctic circle). Large change in radiation means large change in temperature which means more extratropical storms in the winter.</p>
<p>For tropical storms, there is an acronym that I memorized for the necessary (but not sufficient) ingredients for them to develop (the technical term is <a href="https://en.wikipedia.org/wiki/Tropical_cyclogenesis" rel="nofollow noreferrer">tropical cyclogenesis</a>): <strong>LIVERS</strong>.</p>
<ul>
<li><strong>L</strong>atitude- Needs to be small, but not 0</li>
<li><strong>I</strong>nstability- there needs to be a good amount of instability for convection</li>
<li><strong>V</strong>orticity - No vorticity= no spin</li>
<li>(thermal) <strong>E</strong>nergy - The water needs to be warm enough to sustain a tropical cyclone</li>
<li><strong>R</strong>elative Humidity - A (typical) tropical cyclone is moist. <a href="https://journals.ametsoc.org/view/journals/atsc/68/8/2011jas3639.1.xml" rel="nofollow noreferrer">While a dry tropical cyclone is theoretically possible</a>, it is not common, and the barrier for formation is much smaller for a wet tropical cyclone.</li>
<li>(little) <strong>S</strong>hear - An ideal tropical cyclone is symmetrical. Shear disrupts the symmetry (among other issues). That being said, <a href="https://journals.ametsoc.org/view/journals/mwre/146/11/mwr-d-18-0020.1.xml" rel="nofollow noreferrer">it might be easy to overestimate the impact that shear has on weakening an already strengthened tropical cyclone.</a></li>
</ul>
<p>If you consider all of the climate controls for those factors, then you will have a decent grasp of the seasonality of tropical cyclones.</p>
<p>Certainly, storms that are unique to their own locale, such as <a href="https://en.wikipedia.org/wiki/Haboob" rel="nofollow noreferrer">haboobs</a> or the <a href="https://en.wikipedia.org/wiki/Meiyu_front" rel="nofollow noreferrer">Meiyu front</a>, have their own causes and their own seasonality. But in general, if you understand what drives the weather systems, then you can generate how they fluctuate by the season and latitude. Of course, there are exceptions, <a href="https://www.usatoday.com/story/news/world/2020/02/11/baghdad-iraq-snow-winter-storm/4722838002/" rel="nofollow noreferrer">such as the snowfall in Baghdad</a>.</p>

CC BY-SA 4.0
2021-07-14T04:49:20.177Z
So according to that link, extratropical cyclones form between 30-60 latitude, preferentially in December-January for the strongest ones. How does that square with other sources' claims that peak storm season for Japan and Virginia is August-September? Those are both north of 30 degrees.
rwallace
CC BY-SA 4.0
2021-07-14T14:04:41.203Z
Because, the term ‘storm season’ is quite ambiguous. For example, the North Atlantic hurricane season goes from June 1 to November 30., with it peaking between August and October. The peak distribution of typhoons occur in August. And that doesn’t count the Mesoscale Convective Systems/squall lines/derechos, that could contribute to ‘storminess.’
BarocliniCplusplus
CC BY-SA 4.0
2021-07-14T15:12:10.960Z
So comparing e.g. Virginia to Britain, would it be accurate to say that Britain doesn't care about peak hurricane season in August because it's too far north for many hurricanes to reach that far north; Britain thinks peak storm season is December because that's peak for extratropical cyclones...
rwallace
CC BY-SA 4.0
2021-07-14T15:13:19.593Z
but then does Virginia not think of December as peak storm season because a) they get fewer/weaker extratropical cyclones, or b) they get just as many, so just as much December hazard therefrom, but they don't pay so much attention because hurricanes are so much bigger a threat?
rwallace
CC BY-SA 4.0
2021-07-14T15:13:44.427Z
But if it were b) then sailing off the coast of Virginia would be much more dangerous in absolute terms, so I'm guessing the answer is a)?
rwallace
CC BY-SA 4.0
2021-07-14T16:39:38.537Z
I wouldn't say that they don't care about hurricane season, as the UK Met Office does have information about them and makes [seasonal hurricane outlooks](https://www.metoffice.gov.uk/research/weather/tropical-cyclones/seasonal/northatlantic2021).  Having lived, not in Virginia (VA), but both North and South of there, it is more terms of what sort of form will the precipitation take. If you consider precipitation as a measure of storminess, [Norfolk VA](en.wikipedia.org/wiki/Norfolk,_Virginia#Climate) gets more annual precip than [Plymouth, UK](www.plymouth.climatemps.com/precipitation.php).
BarocliniCplusplus
CC BY-SA 4.0
2021-07-15T00:50:39.293Z
Right, in this case what I am actually trying to figure out is hazards for sailing ships, which I suppose would mean wind rather than precipitation? Which latitudes and times of year have the highest hazards for sailing ships?
rwallace
CC BY-SA 4.0
2021-07-14T00:03:02.473Z
2021-07-14T00:03:02.473Z
BarocliniCplusplus
<p>Yes, In he tropics where humidity is more ubiquitous moist air currents feed systems that allow for storms. In temperate climates these storms proliferate where it's warm and humid and die off in winter.</p>

CC BY-SA 4.0
2021-07-14T04:23:11.603Z
2021-07-14T04:23:11.603Z
LazyReader
<p>Anecdotally, where I live in northern Europe, the weather seems to be stormier in winter, and this seems to be backed up by hard data. For example, <a href="https://www.sciencedirect.com/science/article/pii/S0078323411500193?via%3Dihub" rel="nofollow noreferrer">https://www.sciencedirect.com/science/article/pii/S0078323411500193?via%3Dihub</a> discusses the meteorology of the North Sea, confirms storms are more prevalent in winter because of stronger winds. And <a href="https://journals.sagepub.com/doi/full/10.1177/0022526619886061" rel="nofollow noreferrer">https://journals.sagepub.com/doi/full/10.1177/0022526619886061</a> analyzes British coastal trade over the last few centuries, confirms this pattern historically.</p>
<p>But looking at weather patterns in other temperate regions, I seem to be seeing different results; Virginia and Japan are both said to have peak storm season in late summer, August-September.</p>
<p>What's the reason for this difference? I can think of a few possible explanations:</p>
<ul>
<li>The seasonality of storms is different at latitudes 35-40 compared to 50-55.</li>
<li>It's different if you're on the west side of a large continent versus the east side.</li>
<li>It's influenced by quirks of local geography such as the layout of the North Sea versus the Sea of Japan.</li>
<li>The sources are talking about different things. Virginia and Japan are indeed stormiest in winter just like northern Europe if you talk about midrange storms driven by local meteorology; the peak in August-September is not for those kind of storms at all, but for hurricanes that come up from the tropics.</li>
</ul>
<p>What is the explanation for the differing patterns?</p>

CC BY-SA 4.0
2021-07-13T07:29:50.260Z
Hurricanes/Taifuns.
Erik
<meteorology><geography><tropical-cyclone><seasons><mesoscale-meteorology>
Does storm seasonality vary with latitude?
rwallace
# Does storm seasonality vary with latitude?

(Asked by: username_0 on 2021-07-12)

Anecdotally, where I live in northern Europe, the weather seems to be stormier in winter, and this seems to be backed up by hard data. For example, <https://www.sciencedirect.com/science/article/pii/S0078323411500193?via%3Dihub> discusses the meteorology of the North Sea, confirms storms are more prevalent in winter because of stronger winds. And <https://journals.sagepub.com/doi/full/10.1177/0022526619886061> analyzes British coastal trade over the last few centuries, confirms this pattern historically.

But looking at weather patterns in other temperate regions, I seem to be seeing different results; Virginia and Japan are both said to have peak storm season in late summer, August-September.

What's the reason for this difference? I can think of a few possible explanations:

* The seasonality of storms is different at latitudes 35-40 compared to 50-55.
* It's different if you're on the west side of a large continent versus the east side.
* It's influenced by quirks of local geography such as the layout of the North Sea versus the Sea of Japan.
* The sources are talking about different things. Virginia and Japan are indeed stormiest in winter just like northern Europe if you talk about midrange storms driven by local meteorology; the peak in August-September is not for those kind of storms at all, but for hurricanes that come up from the tropics.

What is the explanation for the differing patterns?

**Tags:** meteorology, geography, tropical-cyclone, seasons, mesoscale-meteorology

> **Comments:**
> **username_1**: Hurricanes/Taifuns.  

---

## 2 answers

### Answer by username_2 on 2021-07-14. Score: 3

It really depends on how you define storms. For tropical storms, there are some regions where they are not usually a threat. Likewise, for extratropical storms, there are latitudes where such things are not a concern (such as the tropics). The key to understanding the seasonality to such storms is to understand what controls the seasonality of what drives each.

[Thunderstorms (broadly speaking) rely on a warm air over cooler air](https://en.wikipedia.org/wiki/Convective_instability#:%7E:text=In%20meteorology%2C%20convective%20instability%20or,disturbances%20dampen%20out%20and%20disappear.). During spring and summer that is more likely to happen. More in the spring, as the land and air near the land responds pretty quickly to the increase in radiation, whereas the air further away from the land takes some time to adjust. Air that moves over a cool ocean current will tend to be cooler, so less thunderstorms will usually occur where land is downstream of cool water.

[Extratropical cyclones](https://en.wikipedia.org/wiki/Extratropical_cyclone#:%7E:text=Extratropical%20cyclones%2C%20sometimes%20called%20mid,over%20much%20of%20the%20Earth.) rely on sharp changes in temperature, which is enhanced during winter. That is, the tropics maintain the amount of radiation that they get, while the higher latitudes get less incoming radiation (0 past the Ant/arctic circle). Large change in radiation means large change in temperature which means more extratropical storms in the winter.

For tropical storms, there is an acronym that I memorized for the necessary (but not sufficient) ingredients for them to develop (the technical term is [tropical cyclogenesis](https://en.wikipedia.org/wiki/Tropical_cyclogenesis)): **LIVERS**.

* **L**atitude- Needs to be small, but not 0
* **I**nstability- there needs to be a good amount of instability for convection
* **V**orticity - No vorticity= no spin
* (thermal) **E**nergy - The water needs to be warm enough to sustain a tropical cyclone
* **R**elative Humidity - A (typical) tropical cyclone is moist. [While a dry tropical cyclone is theoretically possible](https://journals.ametsoc.org/view/journals/atsc/68/8/2011jas3639.1.xml), it is not common, and the barrier for formation is much smaller for a wet tropical cyclone.
* (little) **S**hear - An ideal tropical cyclone is symmetrical. Shear disrupts the symmetry (among other issues). That being said, [it might be easy to overestimate the impact that shear has on weakening an already strengthened tropical cyclone.](https://journals.ametsoc.org/view/journals/mwre/146/11/mwr-d-18-0020.1.xml)

If you consider all of the climate controls for those factors, then you will have a decent grasp of the seasonality of tropical cyclones.

Certainly, storms that are unique to their own locale, such as [haboobs](https://en.wikipedia.org/wiki/Haboob) or the [Meiyu front](https://en.wikipedia.org/wiki/Meiyu_front), have their own causes and their own seasonality. But in general, if you understand what drives the weather systems, then you can generate how they fluctuate by the season and latitude. Of course, there are exceptions, [such as the snowfall in Baghdad](https://www.usatoday.com/story/news/world/2020/02/11/baghdad-iraq-snow-winter-storm/4722838002/).

> **Comments:**
> **username_0**: So according to that link, extratropical cyclones form between 30-60 latitude, preferentially in December-January for the strongest ones. How does that square with other sources' claims that peak storm season for Japan and Virginia is August-September? Those are both north of 30 degrees.  
> **username_2**: Because, the term ‘storm season’ is quite ambiguous. For example, the North Atlantic hurricane season goes from June 1 to November 30., with it peaking between August and October. The peak distribution of typhoons occur in August. And that doesn’t count the Mesoscale Convective Systems/squall lines/derechos, that could contribute to ‘storminess.’  
> **username_0**: So comparing e.g. Virginia to Britain, would it be accurate to say that Britain doesn't care about peak hurricane season in August because it's too far north for many hurricanes to reach that far north; Britain thinks peak storm season is December because that's peak for extratropical cyclones...  
> **username_0**: but then does Virginia not think of December as peak storm season because a) they get fewer/weaker extratropical cyclones, or b) they get just as many, so just as much December hazard therefrom, but they don't pay so much attention because hurricanes are so much bigger a threat?  
> **username_0**: But if it were b) then sailing off the coast of Virginia would be much more dangerous in absolute terms, so I'm guessing the answer is a)?  
> **username_2**: I wouldn't say that they don't care about hurricane season, as the UK Met Office does have information about them and makes [seasonal hurricane outlooks](https://www.metoffice.gov.uk/research/weather/tropical-cyclones/seasonal/northatlantic2021).  Having lived, not in Virginia (VA), but both North and South of there, it is more terms of what sort of form will the precipitation take. If you consider precipitation as a measure of storminess, [Norfolk VA](en.wikipedia.org/wiki/Norfolk,_Virginia#Climate) gets more annual precip than [Plymouth, UK](www.plymouth.climatemps.com/precipitation.php).  
> **username_0**: Right, in this case what I am actually trying to figure out is hazards for sailing ships, which I suppose would mean wind rather than precipitation? Which latitudes and times of year have the highest hazards for sailing ships?  

---

### Answer by username_3 on 2021-07-14. Score: 1

Yes, In he tropics where humidity is more ubiquitous moist air currents feed systems that allow for storms. In temperate climates these storms proliferate where it's warm and humid and die off in winter.


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