Atlantic Major Hurricanes Rapidly Intensifying with an Open Eyewall

[Cyclenall]

I remembered one from a few years ago but forgot which, so I asked a few "AI" prompts this question and I doubt the correctness of at least two:

ChatGPT:

Atlantic major hurricanes that rapidly intensify with an open eyewall are those that exhibit a phenomenon where the eyewall of the hurricane remains open and develops significantly in a short period, leading to a rapid increase in wind speeds and central pressure. This process is often associated with extremely favorable environmental conditions such as low wind shear, warm sea surface temperatures, and high atmospheric moisture.

One notable example in recent years is Hurricane Michael (2018):

Hurricane Michael (2018): Michael rapidly intensified from a Category 2 to a Category 5 hurricane in just 24 hours before making landfall on the Florida Panhandle. During this intensification phase, the hurricane maintained an open eyewall, which contributed to its rapid strengthening and devastating impacts.

This phenomenon of rapid intensification with an open eyewall underscores the complexity and intensity of tropical cyclones under optimal atmospheric conditions, posing significant challenges for forecasting and disaster preparedness efforts.

I wrote the same question in weeks ago and it gave me 4 examples at least half were wrong (Matthew/Florence) afaik. I looked at Michael's official report and found nothing about the eyewall being open while RI was in progress. I thought it may have.

Using Brave's AI which most times has been pathetic gave me simply a generic why hurricanes RI and listed Opal/Humberto. I find the prompts will correlate RI to any TC with an open eyewall - ludicrous. I may make a separate topic on how these lame AI prompts are handling hard specific tropical meteorology questions; so far I'm underwhelmed. This is this tool's bread and butter and its failing badly (should have access to most of the TC databases and knowledge).

Atlantic major hurricanes can rapidly intensify, especially when they have an open eyewall . Factors such as warm ocean temperatures, distance from the equator, unstable lapse rate, and low vertical wind shear contribute to this rapid intensification.

[Ubuntwo]

AI hallucination is a notorious problem - but Michael did have an open eyewall for a portion of its rapid intensification, per VDMs.

[Cyclenall]

I revisited this with the improving LLMs so I posed the question to Grok 3:

There is no definitive record in the available data of an Atlantic major hurricane (Category 3 or higher) that underwent rapid intensification (RI, defined as an increase in maximum sustained winds of at least 30 knots or ~35 mph in 24 hours) while maintaining an **open eyewall**. An open eyewall typically indicates a less organized storm structure, often associated with weaker hurricanes or those undergoing disruption due to environmental factors like wind shear or eyewall replacement cycles (ERCs). Rapid intensification, on the other hand, is usually linked to a well-defined, closed eyewall that supports the storm’s strengthening through efficient energy transfer from warm ocean waters.

### Key Points from the Data:
1. **Rapid Intensification and Eyewall Structure**:
- RI is often associated with a robust, closed eyewall where thunderstorms are organized symmetrically around the storm’s center, allowing for efficient intensification.[](https://www.maritime-executive.com/edit ... ore-common)[](https://source.colostate.edu/are-hurric ... e-rapidly/)
- An open eyewall, where the eyewall is incomplete or asymmetric, typically hinders rapid intensification due to reduced organization and weaker inflow of warm, moist air. Storms with open eyewalls are often undergoing structural changes (e.g., ERCs) or are impacted by external factors like wind shear, which disrupt the storm’s core.[](https://www.foxweather.com/learn/eyewal ... s-typhoons)

2. **Hurricanes Studied**:
- The search results highlight several Atlantic major hurricanes that underwent RI, such as Hurricanes Laura (2020), Michael (2018), Harvey, Irma, Maria (2017), Milton (2024), and Wilma (2005). However, none of these are explicitly described as having an open eyewall during their RI phase.[](https://www.maritime-executive.com/edit ... ore-common)[](https://www.severe-weather.eu/global-we ... states-mk/)[](https://eos.org/articles/atlantic-hurri ... ing-faster)
- For example, Hurricane Milton (2024) developed a **pinhole eye** during its RI, indicating a highly organized, closed eyewall structure.[](https://www.severe-weather.eu/global-we ... states-mk/)
- Hurricane Irma (2017) underwent RI with two rapid eyewall replacement cycles, but these cycles typically involve the formation of a new, closed secondary eyewall, not an open one.[](https://journals.ametsoc.org/view/journ ... 0185.1.xml)

3. **Eyewall Replacement Cycles (ERCs)**:
- ERCs, common in strong hurricanes, can temporarily disrupt the eyewall structure as a new eyewall forms outside the original one. During this process, the inner eyewall may weaken or appear less defined, but the storm as a whole doesn’t typically maintain an open eyewall throughout RI. Instead, the new eyewall consolidates, often leading to a closed structure that supports further intensification or stabilization.[](https://journals.ametsoc.org/view/journ ... 0185.1.xml)[](https://www.foxweather.com/learn/eyewal ... s-typhoons)

4. **Environmental and Structural Constraints**:
- Rapid intensification requires favorable conditions like high sea surface temperatures, low wind shear, and high moisture, which promote a symmetric, closed eyewall.[](https://www.maritime-executive.com/edit ... ore-common)[](https://www.gfdl.noaa.gov/global-warmin ... urricanes/)
- An open eyewall is often a sign of environmental stress (e.g., wind shear) or internal dynamics (e.g., ERCs), which are generally incompatible with the sustained, rapid strengthening seen in RI.[](https://www.maritime-executive.com/edit ... ore-common)[](https://eesm.science.energy.gov/researc ... ocean-over)

### Critical Analysis:
- The absence of documented cases in the provided data suggests that RI with an open eyewall is either extremely rare or not well-documented due to observational limitations. Pre-satellite era (before the 1970s) data is less reliable, and even modern observations might not always capture transient open eyewall states during RI.[](https://www.gfdl.noaa.gov/global-warmin ... urricanes/)
- It’s possible that a storm could briefly exhibit an open eyewall during the early stages of RI, especially if transitioning from a disorganized state, but this would likely be short-lived as the eyewall closes to sustain intensification.
- The data’s focus on major hurricanes (Category 3+) that undergo RI emphasizes storms with well-defined structures, so cases with open eyewalls might be underrepresented or not explicitly noted.

### Conclusion:
No Atlantic major hurricanes are explicitly documented in the provided references as having rapidly intensified while maintaining an open eyewall. Rapid intensification typically occurs with a closed, well-organized eyewall, as seen in storms like Milton, Laura, and Wilma. If you’re looking for a specific storm or suspect a rare case might exist, further analysis of individual storm reports (e.g., National Hurricane Center archives) or radar/satellite imagery from less-documented storms could be explored. Would you like me to dig deeper into a specific hurricane or time period?

I've just started testing out Grok and found already its very verbose. It missed Micheal 2018 and the other unknown one I recall a few years ago that would be easily forgotten.

Google Gemini 2.5 Flash:

## The Elusive Link: Rapid Intensification and Open Eyewalls in Atlantic Major Hurricanes

Pinpointing Atlantic major hurricanes that have undergone rapid intensification while simultaneously possessing an open eyewall is a complex task, as readily available comprehensive lists explicitly linking these two specific characteristics are limited. While many major hurricanes experience rapid intensification, and eyewall structures can evolve significantly during a storm's lifecycle, the co-occurrence of a defined "open eyewall" specifically during the period of most rapid strengthening is not always a consistently documented feature in general summaries.

Rapid intensification (RI) is a well-established meteorological phenomenon defined by a tropical cyclone's maximum sustained winds increasing by at least 30 knots (approximately 35 mph) within a 24-hour period. An open eyewall, conversely, describes an eyewall that does not fully encircle the storm's center, often indicating a storm undergoing structural changes, which can include both weakening or, in some transitional phases, strengthening.

While the typical process during significant intensification involves the formation and contraction of a symmetric and closed eyewall, some research and post-storm analyses of notable hurricanes suggest that structural asymmetries, potentially including periods of an open eyewall, can occur during or in conjunction with rapid intensification.

For instance, studies on hurricanes like **Helene (2006)** have noted eyewall *expansion* during its rapid intensification phase, a structural change that could imply a less than perfectly closed eyewall. Similarly, analyses of **Hurricane Dorian (2019)** during its intensification mentioned the role of eyewall formation and asymmetric rainfall structures, which might correlate with periods where the eyewall was not completely closed. **Hurricane Michael (2018)** also exhibited evolving, sometimes polygonal, eyewall shapes during its rapid intensification, another form of asymmetry.

Furthermore, intense hurricanes, including those that have rapidly intensified, often undergo eyewall replacement cycles. This process involves the formation of a new, larger outer eyewall and the dissipation of the original inner eyewall. During the transition phase of an eyewall replacement cycle, the inner eyewall can appear "open" or become less defined before the outer eyewall fully consolidates and contracts. **Hurricane Opal (1995)** and **Hurricane Lee (2023)** are examples of intense hurricanes that underwent rapid intensification and experienced eyewall replacement cycles, suggesting potential periods of a non-closed inner eyewall during or after their most rapid strengthening phase.

However, it is crucial to note that explicit documentation in meteorological reports and research specifically stating "this major hurricane rapidly intensified and had an open eyewall during that precise time" is not commonly compiled into easily accessible lists. Detailed analysis of satellite and radar imagery, along with in-situ observations from reconnaissance aircraft during the rapid intensification period of individual storms, would be necessary to definitively confirm the presence and characteristics of the eyewall at that specific time.

Therefore, while the dynamics of rapid intensification can involve complex structural changes that might include periods of an open or asymmetric eyewall, a comprehensive list of Atlantic major hurricanes definitively meeting both criteria simultaneously is not readily available and would require in-depth meteorological case studies of individual storms. Based on current information, hurricanes like Helene (2006), Dorian (2019), Michael (2018), Opal (1995), and Lee (2023) are potential candidates where such a phenomenon might have occurred at some point during their rapid intensification or subsequent structural evolution, but further detailed analysis is needed for definitive confirmation.

There is some neat reasoning as 2.5 Flash is known for, Helene from 2006 being brought up is intriguing. What I like is reading the thinking dropdown which goes through its process. Here is part of it; I bolded the section why these models are having a tough time with this one:

The search results from step 4 provided some potentially relevant information. Specifically, the search for "Hurricane Helene 2006 rapid intensification eyewall" yielded a result stating that Hurricane Helene (2006) exhibited eyewall expansion during its rapid intensification period, which is a structural change and could imply an open or at least non-symmetric eyewall. The search for "Hurricane Dorian 2019 rapid intensification eyewall" discussed eyewall formation and its link to RI, and also mentioned asymmetric rainfall structures during RI, which might correlate with an open eyewall. The search for "Hurricane Michael 2018 rapid intensification eyewall" mentioned polygonal eyewall evolution during RI, another form of asymmetry. The search for "Hurricane Opal 1995 rapid intensification eyewall" indicated a small, 10 n mi diameter eye at peak intensity after rapid intensification and mentioned an eyewall contraction cycle followed by the diminishment of the inner eyewall as an outer eyewall became more dominant, which is related to eyewall replacement cycles and can involve a temporary open appearance of the inner eyewall. Hurricane Lee (2023) is noted for rapid intensification and undergoing eyewall replacement cycles.

While none of the results explicitly state "major hurricane X rapidly intensified with an open eyewall", the information about eyewall expansion, asymmetric structures, and eyewall replacement cycles during rapid intensification in major hurricanes like Helene, Dorian, Michael, Opal, and Lee suggests that an open eyewall might have been present at some point during their intensification phase, particularly during periods of structural change like eyewall replacement cycles or expansion.

To provide a more definitive answer, the next step should focus on examining detailed analyses or reports of these specific hurricanes during their rapid intensification periods to find explicit descriptions or visual evidence (like satellite or radar imagery analysis) of their eyewall structure, specifically looking for mentions or depictions of an "open eyewall".

Updated plan:
Examine detailed reports or analyses of Hurricanes Helene (2006), Dorian (2019), Michael (2018), Opal (1995), and Lee (2023) during their rapid intensification phases to find explicit mentions or visual evidence of an open eyewall.
If explicit mentions are found, compile the list of these hurricanes.
If explicit mentions are not readily found, explain that while some major hurricanes have shown asymmetric or evolving eyewall structures during rapid intensification that could imply periods of an open eyewall, readily available documentation specifically linking "rapid intensification" and "open eyewall" for major Atlantic hurricanes in a comprehensive list is limited, and further in-depth meteorological analysis of individual storms would be required for a definitive list.
Based on the completed steps and the analysis of the search results, it is challenging to provide a definitive, comprehensive list of Atlantic major hurricanes that have explicitly been documented as having an open eyewall specifically during their period of rapid intensification.

Here's a summary of what the search results indicate:

Rapid Intensification (RI): This is well-defined as a significant increase in wind speed over a short period (typically 30 knots in 24 hours). Many Atlantic major hurricanes have undergone RI.
Open Eyewall: This refers to an eyewall that does not completely encircle the eye and is often associated with changes in intensity or structure.
Connection between RI and Eyewall Structure: The search results highlight that eyewall structure does change during intensification. Some studies mention eyewall contraction as typical during RI, while others point to exceptions like eyewall expansion (Helene 2006) or the development of asymmetric or polygonal eyewalls (Michael 2018, Dorian 2019) during intensification. Eyewall replacement cycles, which can temporarily result in a weakened or open inner eyewall, are also noted as occurring in intense hurricanes and sometimes in conjunction with RI (Opal 1995, Lee 2023).
However, the provided search snippets do not offer a clear list or explicit confirmation for numerous major hurricanes where an "open eyewall" was a defined characteristic precisely during the rapid intensification phase. While structural changes that could lead to an open appearance are mentioned, "open eyewall" isn't consistently used in the summaries of these major hurricanes' rapid intensification periods.

To create a truly definitive list would require a detailed examination of individual storm analyses, including (ideally) access to high-resolution satellite and radar imagery and detailed meteorological reports for the specific hours or days when rapid intensification was occurring, looking for explicit descriptions or visual evidence of an open eyewall during that precise timeframe. This level of detailed analysis is beyond the scope of this tool.

Therefore, while it is likely that some major hurricanes have experienced periods with an open eyewall while also rapidly intensifying, especially during transitional phases like the بداية of eyewall formation or during eyewall replacement cycles, readily available documentation explicitly linking these two specific characteristics for a comprehensive list of major Atlantic hurricanes is not readily found in the search results.

To get closer to an answer, one would need to:

Identify a list of Atlantic major hurricanes that underwent rapid intensification (which the searches have helped with).
For each hurricane on that list, consult detailed post-storm reports (like those from the National Hurricane Center), research papers, and archived satellite and radar imagery to determine the eyewall structure during the specific period of rapid intensification.
Look for explicit mentions or clear visual evidence of an "open eyewall" during that timeframe.
Without conducting this in-depth, storm-by-storm analysis of detailed meteorological data, providing a precise list based solely on the general information in the search results is not possible.

I see some unknown script font thrown in there (its experimental). It didn't bring up VDMs and using that to find when the eyewall would be open and compare to how fast the TC was intensifying.