Science AMA Series: Hi Reddit, I'm Phil Klotzbach, a research scientist in the Department of Atmospheric Science at Colorado State University. I'm here to talk about the 2016 Atlantic hurricane season specifically as well as any other hurricane/typhoon related questions you have. Ask me anything!

Abstract

I am Phil Klotzbach, a research scientist in the Department of Atmospheric Science at Colorado State University. I worked for over 15 years with the late Dr. Bill Gray, a renowned scientist who conducted groundbreaking studies in hurricane genesis, structure and intensity change as well as pioneering Atlantic basin seasonal hurricane prediction. While our Tropical Meteorology Project is best known among the general public for the seasonal hurricane predictions, I conduct research on a variety of hurricane-related topics including shorter-term prediction as well as potential future changes in tropical cyclone activity driven both by natural variability as well as anthropogenic causes. I maintain a very active presence on social media through my Twitter feed (@philklotzbach) where I provide frequent updates on current global tropical cyclone activity and compare them with historical statistics. I also maintain global real-time hurricane statistics. In cooperation with the Barcelona Supercomputing Centre, I helped create a repository of all publicly-available seasonal hurricane forecasts for the Atlantic basin from various government agencies, universities and private forecasting companies.

Currently, I am working on a variety of research projects, including the generation of an updated global tropical cyclone climatology as well as a paper on the life and legacy of Dr. Gray. I am also closely monitoring the potential shift away from the active Atlantic hurricane era that we have been in since 1995. I was lead author on a paper last year that raised the question that we might be moving out of the active era for Atlantic hurricanes.

I look forward to chatting with you about all things hurricane!

I’ll be back at noon EST (9 am PST, 5 pm UTC) to answer your questions, ask me anything!

We've been seeing some news reports about how global warming is expected to make hurricanes worse in the coming century. I'm concerned that such claims may not be well supported by the science. I build and run numerical simulations of electromechanical systems for my job. As such, I know that its important not to ask a question of a model that the model hasn't been designed to answer. I'm concerned that there are variables involved in hurricane formation that the climate models may not have been designed to answer, and that public-facing climatologists are going out on a weak limb when they claim that hurricanes will get worse going forward. As I understand it, the points in favor (of stronger and more damaging storms) are:

  • Higher baseline sea level means that storm surge + high tide bring the sea farther inland.
  • Warmer oceans mean more heat available for powering hurricanes.

But there are many other factors involved that the climate-scale models may not be capturing, or that the model runs aren't being inspected for these features. Things that I know about as a layman include:

  • Vertical wind shear can kill a storm that otherwise has plenty of available energy.
  • Ingesting the Saharan Air Layer can rob a storm of valuable atmospheric moisture.
  • Upper level atmospheric steering patterns may change, leading to fewer (or more) storms making landfall.
  • Climate-scale models are typically run at a lower resolution, so that 100's of years can be simulated in a reasonable time. While climate models are closely related to weather models, IIUC climate-scale model runs aren't even capable of generating hurricanes.

My question: Are the other changes in wind and air mass patterns favorable or unfavorable for hurricane formation and steering as the CO2 levels continue to rise? Do we even know right now?

gruehunter

This is a topic that is still under significant debate in the field. Chris Landsea at the National Hurricane Center and I wrote a paper looking at observed trends in Category 4-5 hurricanes over the past 30 years: http://tropical.atmos.colostate.edu/Includes/Documents/Publications/klotzbachlandsea2015.pdf The challenge is that there is only a limited observational period on which to look for trends. Prior to the mid 1980s, the satellite imagery that is critical to assessing hurricane intensity was at very limited resolution, and consequently, a storm’s intensity was typically underestimated. It is hard to find trends in a 30-year timeseries though, since there is large year-to-year variability driven by fluctuations in climate modes such as El Niño. While El Niño tends to reduce storm activity in the Atlantic, it increases storm activity significantly in the North Pacific. Since the North Pacific dominates in a hemisphere sense, El Niño years tend to have more major (Category 3+ on the Saffir-Simpson Wind Scale) hurricane activity overall. Regarding climate models, there is quite a bit of uncertainty as to how things may change in a warmer world. While hurricanes obtain their fuel from warm sea surface temperatures, it is not just the sea surface temperatures but temperatures at upper levels in the atmosphere that determine the intensity of a hurricane. Kerry Emanuel at MIT developed his potential intensity theory of tropical cyclones about 30 years ago and argued that the maximum intensity that a tropical cyclone could achieve was related to its sea surface temperature, its upper level temperature, along with the atmospheric temperature/moisture profile. Since upper-level temperatures are likely to warm more than surface temperatures in a CO2-warmed world, the increase in hurricane potential intensity may be reduced somewhat. In addition, as you already alluded to, there is a lot of uncertainty as to what future wind shear patterns are going to look like around the globe. There is not yet a model consensus as to what the future state of El Niño is going to be. Consequently, we don’t really know what wind shear in the future will look like. For example, Tom Knutson at the Geophysical Fluid Dynamics Laboratory and collaborators wrote a paper in 2008 that found a decrease in future Atlantic hurricane frequency. Apologies, but the paper is behind a paywall.

http://www.nature.com/ngeo/journal/v1/n6/pdf/ngeo202.pdf

A thorough review paper has recently been written on TCs and climate change as well. I recommend this paper for the current state of the science:

http://onlinelibrary.wiley.com/doi/10.1002/wcc.371/epdf


My five year old son was fascinated by the recent hurricane news. So we tracked the wind maps and other projections of Hurricanes Matthew and Nicole on NHC and watched some videos online. Do you have any recommendations on sources for young kids who want to understand hurricanes and weather in general better?

bloggingsbyboz

There are a bunch of good online resources. I've always liked Weather Wiz Kids:

http://www.weatherwizkids.com/weather-hurricane.htm

The University Corporation for Atmospheric Research has a good website as well:

https://eo.ucar.edu/kids/dangerwx/hurricane1.htm

FEMA also has a nice hurricane website for kids:

https://www.ready.gov/kids/know-the-facts/hurricanes


Hey Phil, What’s something interesting about hurricanes/typhoon you would like to share?

menohero

One thing I find interesting is the negative relationship between Atlantic hurricanes and Northeast Pacific hurricanes. In general, when Atlantic activity is active, Northeast Pacific tends to be suppressed, and vice versa. This works both on a sub-seasonal basis as well as on a seasonal basis. It is very rare to have above-average seasons in both basins. With that being said... 2016 is a year where this has occurred!


  1. How is the severity of a hurricane/typhoon season predicted?

  2. What sort of indicators factor into the prediction?

  3. Is there a metric for categorizing a season after the fact?

shutupshake

1 and 2) A large variety of factors are utilized by various forecasting groups. Our group at CSU bases its forecasts for the Atlantic on the state of ENSO, Atlantic basin water temperatures, Atlantic pressures, wind speeds, etc. A recent summary of global seasonal forecasts is given here:

https://www.wmo.int/cycloneguide/

Feel free to check out our research project's website for more details on CSU's forecasts:

http://tropical.colostate.edu

3) NOAA verifies its seasonal forecasts based on a variety of metrics including the number of named storms, hurricanes and major hurricanes. They also utilize an index known as Accumulated Cyclone Energy. This index takes into account the frequency, intensity and duration of hurricanes:

https://en.wikipedia.org/wiki/Accumulated_cyclone_energy

I also keep track of global TC statistics in realtime here:

http://tropical.atmos.colostate.edu/Realtime/


I work for a local government in central Florida and with Hurricane Matthew seemingly bearing down on us last week there was a bit of a scramble to get information out to the public. I work in the GIS department so we were ready with all kinds of maps, both paper and web-based. I'm mostly curious how GIS is used and seen in your field. Is it seen as a useful tool or more of an extension of modeling systems already in place? Thanks!

Napalmradio

I use GIS quite a bit in my research. I was a Geography major as an undergraduate. One of my undergraduate professors used to say that once we graduated, we needed to be geo-evangelists!

Personally, I feel that GIS is somewhat under-utilized in our field. I try to incorporate it quite a bit into my peer-reviewed papers as well as in various postings that I produce via my Twitter feed. I find GIS extremely useful when working on hurricane/climate projects, including a global TC climatology paper that I'm currently working on. I've got two GIS experts working on the paper with me who make WAY better maps than I do too!


Thanks for doing an AMA. What breakthroughs in weather forecasting do you think will happen within your lifetime?

I'm fairly new to models but I hear people say "ohhh this model is good for tropical systems but it can't model it as well when it goes post tropical" like Matthew did when it turned into more of a nor'easter. Why is that?

ava_ati

As computational power continues to grow, we should be able to run our models at higher and higher resolution. This should help us to better be able to model the internal workings of hurricanes. One of the challenges with current numerical models is that they struggle to handle some of the changes in hurricane structure, such as eyewall replacement cycles.

As we get new weather satellites such as GOES-R, which should be launched in the next few weeks, we should be able to also achieve a better understanding of the current weather conditions around the globe. As I discussed in my answers to previous questions, a more accurate understanding of initial conditions leads to more accurate weather forecasts.

http://www.nesdis.noaa.gov/GOES-R/

All in all, forecasts from weather models have significantly improved over the past 10-20 years, and I would expect that these improvements will continue in the future.


Hi, I don't follow your research so maybe this is a basic question, but could you talk a little bit about what you mean by us moving away from an active Atlantic hurricane era?

madroaster

In general, the large-scale atmospheric/oceanic conditions in the Atlantic have become less conducive for hurricane formation over the past four years. This is due to a variety of factors including generally higher pressure and associated sinking motion in the tropical Atlantic, dryer air at mid levels and slightly cooler sea surface temperatures. 2016 was behaving like a quiet season as well, until the past two weeks, when Hurricanes Matthew and Nicole have rapidly increased aggregate tropical cyclone activity numbers. The paper that I published last year discussing the end of the active era is available here:

http://tropical.atmos.colostate.edu/Includes/Documents/Publications/klotzbachetal2015.pdf


Thank you for doing this 2 questions 1)Do you think there is any feasible way to "control" hurricanes by directing their pat? 2) Would there be an effecient way of absorbing their power for our own power grid?

bonerfiedmurican

NOAA undertook an extensive project to modify hurricanes back in the 1960s called Project Stormfury. The idea was that seeding clouds with silver iodide would disrupt the inner core of the circulation:

https://en.wikipedia.org/wiki/Project_Stormfury

This hurricane modification project did not show any significant success in modifying hurricane strength, although this project did significantly improve our understanding of how hurricanes function. I think the primary issue with most hurricane modification schemes is that they suffer from a scale perspective. Hurricanes are too large for most of these techniques to work.

However, my recently deceased boss and mentor Dr. Gray would argue up and down that by seeding the outer bands of hurricanes with carbon black, we could enhance the outer bands of hurricanes, consequently weakening the inner core of the circulation.

https://dspace.library.colostate.edu/bitstream/handle/10217/98/0196_Bluebook.pdf?sequence=1


As the Earths temperature rises how much of a factor does global warming play into the process of predicting the magnitude of future hurricanes?

559Monster

I responded to this question in considerable detail above. I've pasted my response here for convenience:

This is a topic that is still under significant debate in the field. Chris Landsea at the National Hurricane Center and I wrote a paper looking at observed trends in Category 4-5 hurricanes over the past 30 years: http://tropical.atmos.colostate.edu/Includes/Documents/Publications/klotzbachlandsea2015.pdf The challenge is that there is only a limited observational period on which to look for trends. Prior to the mid 1980s, the satellite imagery that is critical to assessing hurricane intensity was at very limited resolution, and consequently, a storm’s intensity was typically underestimated. It is hard to find trends in a 30-year timeseries though, since there is large year-to-year variability driven by fluctuations in climate modes such as El Niño. While El Niño tends to reduce storm activity in the Atlantic, it increases storm activity significantly in the North Pacific. Since the North Pacific dominates in a hemisphere sense, El Niño years tend to have more major (Category 3+ on the Saffir-Simpson Wind Scale) hurricane activity overall. Regarding climate models, there is quite a bit of uncertainty as to how things may change in a warmer world. While hurricanes obtain their fuel from warm sea surface temperatures, it is not just the sea surface temperatures but temperatures at upper levels in the atmosphere that determine the intensity of a hurricane. Kerry Emanuel at MIT developed his potential intensity theory of tropical cyclones about 30 years ago and argued that the maximum intensity that a tropical cyclone could achieve was related to its sea surface temperature, its upper level temperature, along with the atmospheric temperature/moisture profile. Since upper-level temperatures are likely to warm more than surface temperatures in a CO2-warmed world, the increase in hurricane potential intensity may be reduced somewhat. In addition, as you already alluded to, there is a lot of uncertainty as to what future wind shear patterns are going to look like around the globe. There is not yet a model consensus as to what the future state of El Niño is going to be. Consequently, we don’t really know what wind shear in the future will look like. For example, Tom Knutson at the Geophysical Fluid Dynamics Laboratory and collaborators wrote a paper in 2008 that found a decrease in future Atlantic hurricane frequency. Apologies, but the paper is behind a paywall.

http://www.nature.com/ngeo/journal/v1/n6/pdf/ngeo202.pdf

A thorough review paper has recently been written on TCs and climate change as well. I recommend this paper for the current state of the science:

http://onlinelibrary.wiley.com/doi/10.1002/wcc.371/epdf


What are the advances in predicting hurricanes?

PavelD500

Numerical models have shown significant improvements, especially in being able to predict the tracks of hurricanes. These improvements have reflected in dramatically improved skills by the National Hurricane Center. There is an extensive set of verification data available on NHC's website:

http://www.nhc.noaa.gov/verification/verify5.shtml

For example, a 3-day forecast in 1970 had an average error of approximately 450 nautical miles, while a 3-day forecast in 2015 had an average error of only 150 nautical miles.

As the model resolution improves and we get improved observational data from satellites and surface stations, I expect that this forecast skill will continue to improve.

The intensity skill for hurricane prediction has not improved as quickly. That is because being able to predict the future intensity of a hurricane not only involves getting the large-scale correctly but also knowing the internal dynamics of the storm. Predicting rapid intensification of hurricanes (e.g., like what happened in Matthew), is still extraordinarily difficult. As you can see in the previous link that I sent you, intensity forecasts are slowly improving. The Hurricane Forecast Improvement Project (HFIP) has been started by NOAA to hopefully increase the skill of intensity forecasts, while also improving the skill of track forecasts:

http://www.hfip.org/


Why can't we call them the same thing no matter what ocean they are in? Is there really a functional difference between a typhoon, a cyclone, and a hurricane beyond their location?

SednaBoo

It is primarily due to historical terms that have been used in various areas. For reference, they are called hurricanes in the North Atlantic and Northeast Pacific, typhoons in the Northwest Pacific and cyclones in the remainder of the globe's tropical cyclone basins. As one of the responders already noted, the generic term is tropical cyclone.


Howdy! Thanks for doing this AMA. I am a huge weather nerd (and amateur atmospheric scientist) so this AMA will be great to follow.

Do you have a favorite hurricane or typhoon? In other words, is there one particular tropical system that just engages you due to the cultural aspects of it, the science learned from it, etc?

spacegurl07

Hurricane Gloria (1985) was a game-changing hurricane for me, as it was the hurricane that really got me focused on hurricanes. I was growing up in southern New England at the time that it hit.

Also Hurricane Patricia last year in the Northeast Pacific was an amazing storm to watch. Watching a hurricane intensify that rapidly was incredible! Fortunately, it made landfall in a national park, which while causing significant damage where it made landfall, minimized overall damage and loss of life that it caused. I can only imagine how much damage that storm would have done if it had hit a highly populated area!


Hi I am from the st Augustine/Jacksonville part of north Florida... we just had Hurricane Matthew.

What was the difference between that category 4/5 storm compared to Hurricane Andrew in the 90's category 4/5 storm?

Once the storm hit us, even at 3 it just seemed like it was a bit calmer than people made it out to be. Thoughts?

lurkcityfl

Fortunately, the eyewall of Matthew stayed offshore, and consequently, the strongest winds also remained offshore. The Florida coastline did not experience major hurricane-force winds.


What has made you to pursue your current profession? Also, what do you love the most about it?

Hearthsynkrz

I've always been fascinated by the weather, since I was a small child. Hurricane Gloria (1985) impacted my family when I was growing up in southern New England, and that storm helped focus my interests in hurricanes. I think what's most fascinating about the job is that each hurricane is different, and each one is certainly a learning experience!


What factors do you use to predict the severity of an upcoming hurricane season, and how early in the year are you able to start making these predictions?

tdschwarz

A large variety of factors are utilized by various forecasting groups. Our group at CSU bases its forecasts for the Atlantic on the state of ENSO, Atlantic basin water temperatures, Atlantic pressures, wind speeds, etc.

Feel free to check out our research project's website for more details on CSU's forecasts:

http://tropical.colostate.edu

Our first seasonal forecast comes out in early April, with improved skill for our forecasts issued in early June and August.


Hi, Phil. Thanks for your AMA. Before it's start Matthew was expected to be one of the strongest hurricanes in history, but on wikipedia I've read that it spent 6 hours as Cat.5. So it didn't live up to the expectations, did it (or category isn't only measure of hurricane's strength)? Did something cause it to shrink and everyone got lucky, or was the prediction wrong?

alexeusgr

Matthew was a very impressive long-lived major hurricane. It actually intensified more than most of the models were predicting. While it was in a very conducive environment for intensification, there have certainly been more conducive environments than what Matthew intensified in. Matthew achieved quite a few notable records that I've detailed here:

https://webcms.colostate.edu/tropical/media/sites/111/2016/10/matthew.pdf

For example, while it was only a Category 5 for six hours, it was a Category 4-5 hurricane for 102 hours in October - the longest stretch on record for an Atlantic hurricane in October.


Dr. Klotzbach, thanks for doing this AMA! I have a few questions:

1) Do you have an opinions on the reliability of GCM downscaling? It seems that if you are looking into variability of future TC activity, this would be an important aspect, and it doesn't sit right in my mind that we can use potentially physically uncorrelated GCM outputs to predicts something of use at a smaller-then-gridbox scale.

2) Can you elaborate on what you mean when you say "the generation of an updated global tropical cyclone climatology"?

Thanks again!

brachunok

I also tend to have reservations about downscaling GCMs as a tool for understanding future hurricane changes. I tend to stay out of the modeling field and stick to looking at observed changes.

As observational practices have changed over the years, we have generally detected more storms globally. For example, when Dr. Gray published his first global climatology paper in 1968, he calculated an average of 62 named storms per year, while using modern date, the number is between 80-90. Our paper updates these global tropical cyclone numbers with a recent 30-year period from 1985-2014 and also includes analysis of how ENSO impacts these storms globally among other topics.


I heard an interesting fact in the news today, Bermuda had only had 4 major hurricane warnings in the past couple of years. If this is true, and it lies in the Atlantic, what contributes to being missed by the storms so much? It seems when the storms are done coming up the Caribbean and Florida, they always take a North-easterly route towards where Bermuda would be to eventually dissipate. Being that it still has some waters around that area, would they not just strengthen?

Gekinwired24

Bermuda is no stranger to hurricanes, but it is relatively rare for major hurricanes to impact the island. For example, I calculated 6 hurricanes tracking within 50 miles of Bermuda at 100 mph or stronger since 1950. Nicole is the 7th. Typically, SSTs do begin to cool by the time you get to Bermuda, and vertical shear begins to increase. So, hurricanes can survive at that latitude, but they tend to be weakening by that point.


I've always wondered, who gets to name a hurricane (Mathew, Katrina etc.)?

Chryzonicus

The storm naming process is governed by an international committee of the World Meteorological Organization:

http://www.wmo.int/pages/prog/www/tcp/Storm-naming.html


Hi cousin Phil! It's Katie K _^

I don't have a highly technical question to ask but I'm excited you're here. When it comes to the naming process, is there a vote? A committee? Does one person have veto power? And does anything culturally relevant get taken into account when choosing (or dismissing) names?

ivy-and-twine

Hey Katie! Hope you're doing well. The World Meteorological Organization of the United Nations is the over-arching committee for naming these storms:

http://www.wmo.int/pages/prog/www/tcp/Storm-naming.html

These names get recycled every six years unless a storm causes a lot of damage (e.g., Hurricane Katrina).


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