<p>Yes, two or even more rarely, three tropical storms or hurricanes / typhoons can merge, and have done so in nearly all the major ocean basins where sea surface temperatures exceed 27 deg C. As far as I know this has never been observed in the South Atlantic (can anyone confirm this?). The result of a tropical storm merger is initially determined by 'conservation of angular momentum'. As the storm progresses, it either weakens or strengthens in the usual way, That is, according to (a) the available latent heat of evaporation, which in turn is a function of sea surface temperature beneath the storm footprint, and (b) whether kinetic energy is dissipated as friction over land.  </p>

CC BY-SA 3.0
2015-10-02T11:27:18.837Z
2015-10-02T11:27:18.837Z
Gordon Stanger
<p>I was just reading <a href="https://en.wikipedia.org/wiki/1964_Atlantic_hurricane_season#Hurricane_Ethel">this</a> about how Hurricane Ethel could have merged with Hurricane Dora in 1964.</p>

<p>Has such a merge ever happened before in history? If so, what was the result? Would storms become twice as powerful? Or would they disrupt and dissipate each other?</p>

<p>They don't have to be hurricanes or typhoons <em>per se</em>, just large storms. I would think the low pressure regions of two storms would tend to attract each other if they were nearby, but it's apparently rare or unheard of because a quick google search showed nothing.</p>

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2016-10-21T02:10:27.630Z
Early tropical cycylones generally form as localized vortices merge (look up vortical hot towers).  But for large storms to merge, their structures would have to merge, and generally that would disrupt their rather fragile cores, and almost certainly weaker a TC for a long while.  In theory the increased warm core\decreased pressure could lead a stronger storm eventually.  But TCs can grow quite rapidly on their own in favorable conditions, such that the disruption a merger would cause would probably not be the extraordinary event you'd think.
JeopardyTempest
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2016-10-21T02:18:13.010Z
Now, on the other hand, baroclinic systems can and regularly do merge and intensify, as they are driven by their temperature gradients, not the warm core at the center of a TC.  The warm core needs continual nearby vigorous updrafts, and secondary pressure areas typically disrupt the necessary convergence to maintain this.  Extratropical lows just need the temperature gradient, and so doesn't require continual convection to sustain... generally mergers can combine their gradients easily without much disruption to the storm.
JeopardyTempest
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2016-10-21T02:29:48.497Z
So 2 TCs merging don't generally occur favorably.
JeopardyTempest
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2017-03-24T15:06:35.713Z
@gansub I can't say I have formal research, no. I have spent my share of time applying tropical meteorology. My focus has always been Atlantic (and occasionally EPac\WPac) storms, where it seems, from my experience, that when storms are closely located, they're disrupted, similar to how developing storms typically struggle with multiple centers. But I'm willing to be wrong, and will certainly defer if you're more expert. Indeed I never took my coursework on into operations or research, so I certainly could miss things not being involved daily. I'd be interested to see examples of such mergers
JeopardyTempest
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2017-03-24T17:47:53.750Z
@gansub, but seems it would be a question of expertise when research lacks, as it did for me. I believe I was mistaken and had considered this a new question without answers when I commented, which is one me. Your idealized/basin climatology information is great, and more helpful than anything I said. I'll add further comments there...
JeopardyTempest
CC BY-SA 3.0
2015-09-07T02:07:59.533Z
@gansub great reference, you should turn it into an answer :)
casey
<meteorology><tropical-cyclone>
Have two hurricanes ever merged? And what was the result?
DrZ214
# Have two hurricanes ever merged? And what was the result?

(Asked by: username_0 on 2015-09-06)

I was just reading [this](https://en.wikipedia.org/wiki/1964_Atlantic_hurricane_season#Hurricane_Ethel) about how Hurricane Ethel could have merged with Hurricane Dora in 1964.

Has such a merge ever happened before in history? If so, what was the result? Would storms become twice as powerful? Or would they disrupt and dissipate each other?

They don't have to be hurricanes or typhoons *per se*, just large storms. I would think the low pressure regions of two storms would tend to attract each other if they were nearby, but it's apparently rare or unheard of because a quick google search showed nothing.

**Tags:** meteorology, tropical-cyclone

> **Comments:**
> **username_2**: @gansub great reference, you should turn it into an answer :)  
> **username_1**: Early tropical cycylones generally form as localized vortices merge (look up vortical hot towers).  But for large storms to merge, their structures would have to merge, and generally that would disrupt their rather fragile cores, and almost certainly weaker a TC for a long while.  In theory the increased warm core\decreased pressure could lead a stronger storm eventually.  But TCs can grow quite rapidly on their own in favorable conditions, such that the disruption a merger would cause would probably not be the extraordinary event you'd think.  
> **username_1**: Now, on the other hand, baroclinic systems can and regularly do merge and intensify, as they are driven by their temperature gradients, not the warm core at the center of a TC.  The warm core needs continual nearby vigorous updrafts, and secondary pressure areas typically disrupt the necessary convergence to maintain this.  Extratropical lows just need the temperature gradient, and so doesn't require continual convection to sustain... generally mergers can combine their gradients easily without much disruption to the storm.  
> **username_1**: So 2 TCs merging don't generally occur favorably.  
> **username_1**: @gansub I can't say I have formal research, no. I have spent my share of time applying tropical meteorology. My focus has always been Atlantic (and occasionally EPac\WPac) storms, where it seems, from my experience, that when storms are closely located, they're disrupted, similar to how developing storms typically struggle with multiple centers. But I'm willing to be wrong, and will certainly defer if you're more expert. Indeed I never took my coursework on into operations or research, so I certainly could miss things not being involved daily. I'd be interested to see examples of such mergers  
> **username_1**: @gansub, but seems it would be a question of expertise when research lacks, as it did for me. I believe I was mistaken and had considered this a new question without answers when I commented, which is one me. Your idealized/basin climatology information is great, and more helpful than anything I said. I'll add further comments there...  

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## 1 answers

### Answer by username_3 on 2015-10-02. Score: 3

Yes, two or even more rarely, three tropical storms or hurricanes / typhoons can merge, and have done so in nearly all the major ocean basins where sea surface temperatures exceed 27 deg C. As far as I know this has never been observed in the South Atlantic (can anyone confirm this?). The result of a tropical storm merger is initially determined by 'conservation of angular momentum'. As the storm progresses, it either weakens or strengthens in the usual way, That is, according to (a) the available latent heat of evaporation, which in turn is a function of sea surface temperature beneath the storm footprint, and (b) whether kinetic energy is dissipated as friction over land.


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