Cyclones and Warnings and Names, Oh My!

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Visible satellite image of Tropical Storm Bill at 10:15 am CDT on Tuesday, June 16, just before it made landfall along the Texas coast on Matagorda Island.

The development of Tropical Storm Bill so close to the Texas coast, with the posting of a formal tropical storm warning only about 12 hours before winds of that intensity came ashore on Tuesday June 16th, highlighted a long-standing and well-known limitation in the tropical cyclone program of the National Weather Service (NWS).  An ongoing NHC initiative to improve service for such systems is the subject of today’s blog post.

Although there’s nothing new about a tropical cyclone forming on our doorstep, what is new is an increased ability to anticipate it.  NHC has greatly enhanced its forecasts of tropical cyclone formation over the past several years, introducing quantitative 48-hr genesis forecasts to the Tropical Weather Outlook in 2008, and extending those forecasts to 120 hours in 2013.  In 2014, we introduced a graphic showing the locations of tropical disturbances and the areas where they could develop into a depression or storm over the subsequent five days.  Thirty-six hours in advance of Bill’s formation, NHC gave the precursor disturbance a 60% chance of becoming a tropical cyclone, and increased that probability to 80% about 24 hours in advance.  While nothing was guaranteed, we were pretty confident a tropical storm was going to form before the disturbance reached the coast.  And although we weren’t issuing specific track forecasts for the disturbance, NHC’s new graphical Tropical Weather Outlook (example below) showed where the system was generally headed.

Bill_two_atl_5d0

We wouldn’t have had such confidence 20 years ago, or even 5 years ago. And so our tropical cyclone warning system, developed over several decades, doesn’t allow for a watch or warning until a depression or storm actually forms and NHC’s advisories begin; by both policy and software, warning issuances are tied to cyclone advisories.  If we had wanted to issue a tropical storm watch for Bill on the morning of Sunday the 14th (48 hours prior to landfall), or a warning that evening (36 hours ahead of landfall), we would have had to pretend that the disturbance in the Gulf of Mexico was a tropical cyclone.  Even during the day on Monday, data from an Air Force Reserve Hurricane Hunter aircraft showed that the disturbance had not yet become a depression or storm.

Couldn’t NHC have called the disturbance a tropical storm anyway, in the interest of enhanced preparedness?  Yes, but what if the disturbance never becomes a tropical storm – remember, even an 80% chance of formation means it won’t become a tropical storm at least once every five times.  So naming it early risks the credibility of the NWS and NHC, and endangers a trust we’ve worked for decades to establish.  In addition, there are legal and financial consequences to an official designation of a tropical cyclone – consequences that obligate us to call it straight.  And finally, as custodians of the tropical cyclone historical record, we have a responsibility to ensure the integrity of that record.

When systems that have the potential to become tropical cyclones pose hazards to life and property, NHC’s best avenue for highlighting those hazards currently is the Tropical Weather Outlook. Ahead of Bill’s formation, the possibility of tropical storm conditions along the middle and upper Texas coast was included in the Sunday evening Outlook, and by early Monday afternoon the Outlooks were saying those conditions were likely.  Products issued by NWS local forecast offices (WFOs) carried similar statements.

Although most folks seemed to have gotten the message that a tropical storm was coming, it’s widely thought that the Tropical Weather Outlook and local WFO products don’t carry the visibility and weight of an NHC warning, or of an NHC advisory package with its attendant graphics.  In addition, some institutions have preparedness plans that are tied to the presence of warnings.  We agree that warnings during the disturbance stage could improve community response, and we’ve been working toward that goal since 2011.  In that season, NHC initiated an internal experiment in which the Hurricane Specialists prepare track and intensity forecasts for disturbances with a high likelihood of development, and use these forecasts to determine where watches and warnings would have been appropriate.  These internal disturbance forecasts have had some successes and failures, but may now be good enough to make public.

With our colleagues across the NWS, we’re now working through the logistics of expanding the tropical cyclone product and warning suite to accommodate disturbances.  One plan under consideration calls for NHC to produce a five-day track and intensity forecast for those disturbances having a high chance of becoming a tropical cyclone, and which pose the threat of bringing tropical-storm-force winds to land areas.  The forecasts would be publicly issued through the standard NHC advisory products, including the Public Advisory, Discussion, and Wind Speed Probability Product, along with the forecast cone and the other standard graphics. These advisory packages would be issued at the normal advisory times, and continue until the threat of tropical-storm-force winds over land had diminished.  If and when the disturbance became a tropical cyclone, advisory packages would simply continue.

We are still evaluating these and other options for getting tropical cyclone warnings out for potential tropical cyclones.  If we do begin issuing forecasts for these systems, we know from our experimental forecasts that they won’t be as accurate as our current public forecasts for tropical cyclones are – and we’ll want to make sure users know about those uncertainties.  There are many details to iron out and much technical work to do, but we’re hopeful to have this service enhancement in place for the 2017 hurricane season.

— James Franklin
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13 thoughts on “Cyclones and Warnings and Names, Oh My!

    Lane Ponsart said:
    July 21, 2015 at 1:31 AM

    Mr. Franklin,

    Thank you so much for expanding on this publicly. In general, the plan seems like an excellent idea, but as mentioned in your entry, has many caveats.

    My two cents regarding the possibility of the NHC doing something like this much prefers NHC doing so in a manner consistent with other governmental forecasting agencies, such as the SPC, and stick to issuing a Watch only, until it becomes clear that ‘Conditions strongly favoring the development of a named tropical cyclone’ have indeed verified (i.e. a storm has formed – or a depression has formed that is robustly expected to then become a named storm).

    In my opinion, sticking to issuing a Watch product for disturbances that have a high likelihood of development, only to be upgraded to a Warning if and when conditions fully warrant, would be the easiest policy to explain to the public, given that the public is already growing more and more familiar with the differences between Watches – which usually cover a much larger region up to days in advance for the high potential of a given event – than the more specific locations covered when active Warnings within a given Watch have been issued.

    It seems to me that if only going with ‘a five-day track and intensity forecast for those disturbances having a high chance of becoming a tropical cyclone, and which pose the threat of bringing tropical-storm-force winds to land areas,’ unnecessary confusion and damaged confidence may ensue, as the public is fully accustomed to seeing those products only issued for *developed* and *warned* tropical cyclones.

    Respectfully,

    Lane Ponsart

    P.S. Thank you all for the incredible work you do and science you share. Improvements the NHC has made over the years have been phenomenal!

    Daniel Isaac said:
    July 21, 2015 at 11:51 AM

    Thanks for your article, Mr Franklin. What about issuing a Tropical Cyclone Formation Alert when likelyhood equals or exceeds 60% chance, like the JTWC does?

    James Franklin responded:
    July 21, 2015 at 12:26 PM

    Lane, thank you for the thoughtful comments and your kind words. We are also concerned about damaging user confidence, particularly since we know our forecast errors for these systems will be somewhat higher than those for actual tropical cyclones. But on balance we feel that providing residents enough time to respond to developing tropical storms (and potentially hurricanes) is a benefit that warrants taking that risk.

    NHC’s warning paradigm has always been different from SPC’s. SPC issues severe weather watches and then local WFOs issue the warnings. That type of division of responsibility has never been part of the tropical program, where NHC is responsible for both the coastal watches and the warnings. We also differ from SPC in that we have international responsibilities. It is well established, both in the United States and the other countries of the hemisphere, that a Tropical Storm Warning means that tropical storm conditions are “expected” while a Watch means only that those conditions are “possible”. If a developing disturbance were approaching the coast, had or was expected to have tropical-storm-force winds, and we also had a high degree of confidence that a cyclone would form – using a Watch would be in plain contradiction to the Watch definition. In short, we don’t want to be suggesting to folks that some hazard is “possible” if we really want to convey that it is expected. And it’d be hard to explain to folks that a Watch sometimes means “expected” and other times it only means “possible”.

    James

    James Franklin responded:
    July 21, 2015 at 12:29 PM

    Daniel, I think the JTWC TCFA is pretty much covered already in our Tropical Weather Outlook. Each disturbance is color coded according to genesis likelihood, and turns “red” when the genesis potential gets to 70% (last year it was 60%). Would a JTWC-like TCFA convey anything new?

    James

    Lemuel Taylor said:
    July 21, 2015 at 5:59 PM

    This explains a lot. As someone who follows the weather avidly, I’ve always wondered why storms we’re “called” sometimes until the “last minute”. One important thing to remember as was rightfully said is that there is a historical record to be preserved. Accurate history leads to more accurate predictions in future.

    dubhghlas said:
    July 22, 2015 at 8:44 AM

    I think one of the biggest issues is ignorance. Having previously lived in and around the Gulf, I found that plenty of people did not pay attention to the products produced by the NHC, and their only source of tropical related weather information were their local weather or the watch/warnings issued. If a TCFA could be issued in a similar manner that tropical storm and hurricane watches and warnings are issued – that is, disseminated through various avenues your typical weather alerts are issued – this could go a long way in helping educate the general public of potential tropical weather without losing the integrity of TS/H watches and warnings.

    Just my 2¢.

    biff said:
    July 24, 2015 at 9:52 PM

    Responding to the language: above: ” an 80% chance of formation means it won’t become a tropical storm at least once every five times.”

    It is somewhat unfortunate that the 1:5 odds above imply that 1 in each 5 events will … occur or not occur.

    While it may be statistically accurate that this would be true in the long run, in short term, the chances remain 1:5 for each single event! Even if it did not work out that way in the last 50 occurrences!

    Much appreciate the sensitivity however in the discussion about giving people reliable info about potential threats to life and property while maintaining credibility! Agreed also that the whole watch/warning process has indeed improved and share the hopes that more advanced development of computer models will help here…

    Nice going NOAA, NWS and NHC! We need ya and you’re doing us the best possible service with a positive, informative, and encouraging hope for moving the frontiers of forecasting always further along! I especially always admire the humility in the forecast discussions. Very human, yet very straightforward. Mariners friend too…

    Keep it up.

    Biff.

    lynnmagnuson said:
    July 25, 2015 at 3:16 PM

    I think you folks do a GREAT job, but people are critical sometimes because they don’t understand that meteorology, and climatology are very new sciences compared to others that have been out there much longer (physics, chemistry, etc.). As such, there’s still much to learn. So no criticisms here … you work with the information and knowledge you have available to you. More is always being learned about the atmosphere of our planet.

    My question to you is this. What do you think of more educational programs being made available to the public so they can learn more about these new sciences in general. I’ve found very few people I’ve talked with really know what either meteorology or climatology study. I’m talking about more than just explaining what a hurricane is or a watch or warning. Getting into the science a bit more than that. This might help with some of the doubts and skeptism I’ve seen with people concerning hurricanes and their dangers, and the work of the National Hurricane Center.

    Lynn
    New Orleans, LA.

    Barry said:
    July 25, 2015 at 6:36 PM

    Thank you for considering these things! I think the greater issue at hand is that even if a system does not have a closed circulation, it is sometimes already producing onshore winds in excess of the threshold that typically defines a tropical storm, with storm surge, and the torrential rains. If dangerous weather is forecast with a likely scenario, but the system is not a closed low, isn’t the whole point to warn the public of the dangerous weather? A ragged 40 mph tropical storm with a closed circulation and little organized convection poses less threat than a 50 mph piece of convection capable of sustaining itself for a while and causing far more destruction. Yet, we have an entire agency that is dedicated to the purpose of warning about tropical cyclones–an agency staffed by the taxes of those stakeholders who need to know this weather is approaching. The question is:

    -What is the role of the NHC in circumstances where naming a storm is not appropriate in accordance with every meteorological criterion? What more could the NHC do in order to utilize its staffing capacity in those circumstances?

    -Or, is the interest of those insurance agencies which provide specific services in the presence of named storms the more important stakeholder than the awareness of the average coastal citizen?

    Thanks for all you do!

    James Franklin responded:
    July 26, 2015 at 8:18 PM

    Barry, NHC’s forecasting staff is divided into two operational units: the Hurricane Specialist Unit (HSU) and the Tropical Analysis and Forecast Branch (TAFB). The HSU forecasters have expertise in tropical cyclones and so that’s what they do. The TAFB forecasters have expertise in marine forecasting so that’s what they do.

    Neither TAFB nor the HSU has expertise in forecasting land-based hazards for non-tropical cyclones, so it wouldn’t be beneficial to anyone for us to get involved. For such systems, local NWS Weather Forecast Offices provide the appropriate forecasts and warnings for the areas they serve.

    James

    James Franklin responded:
    July 26, 2015 at 8:22 PM

    Lynn, I think it would be great if more people understood meteorology. We do have our hands full just educating folks on the basics of the hurricane hazards though, so that’s our focus. Our off season is packed with all kinds of outreach and education efforts.

    Biff said:
    July 28, 2015 at 12:36 AM

    Brief question: who is managing the new storm swell to landfall projections… Your explanation about the divide and conquer divisions of responsibility was very informative… But in the case of storm surge… some admin boundaries appear to be crossed.

    And, very incidentally, kudos to your team on doing that, whoever does it… Storm surge landfall forecasting is just one more crucial advance in how NOAA, NHC and NWS are helping to save lives and property. Well Done!

    Biff

    Rick said:
    August 26, 2015 at 5:55 PM

    It appears El Nino may cause wind shear to many of the possible hurricanes this year. As Erika approaches it seems it won’t be that strong if it hits Florida. However, it would be prudent to follow it’s development. Puerto Rico may get some needed rain. Knowing how much damage can be caused depending on a storm with a certain hurricane category can be important when making plans for an incoming hurricane.

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