August 30th, 2011
11:23 AM ET

How Irene's forecast missed the mark and why it could happen again

They know they missed it. Forecasters at the National Hurricane Center in Miami say when it comes to the strength of Hurricane Irene as it approached North Carolina, they know they were off. Way off.

“At least in the guidance we were looking at there was no indication of anything that would cause the storm to weaken. So, we thought we would have a Category 3 at landfall,” said Bill Read, the director of the Hurricane Center. Irene came in at a Category 1, the weakest. Read said there’s good reason they were so far off.

The science of forecasting how strong or weak a storm will become is simply not very good. With Irene, forecasters say they weren’t even as good as their five-year average.

“Every storm comes up with a surprise,” Read said. “In this case it was one where it went downhill. Charlie a few years ago is one that went uphill. Neither case did we see that coming, and that’s my measure of the fact that we have a long way to go.”

Bill Read, of the National Hurricane Center, talks about the difficulty of predicting hurricanes.

Hurricane forecasters say they want to get it right all the time. But if you are going to be wrong, they say it's better to be wrong in weakening storms like Irene.

“I’d say a bigger worry than one weakening at landfall is the ’35 hurricane that came through the Keys," Read said. "Charlie if it’s a little bigger. Audrey in 1957. Get the picture?”

In all of these cases, the storms rapidly intensified as they neared the coastline. By then, it’s too late to order massive evacuations.

CNN's severe weather expert Chad Meyers said when Hurricane Irene smashed into the Outer Banks of North Carolina, the contact weakened the storm.

So, forecasters had the path right, but the impact of landfall changed what the amount of destruction would be in some areas. Wind shear helped knock down velocity, and unexpected dry air sucked some of the power out of the storm.

"It literally knocked the stuffing out of the eye," Myers said. "It never got its mojo back."

Meteorologists measured pressure levels inside the storm that could have allowed it to strengthen back into a Category 3 hurricane, Myers said, but Irene's romp over land in North Carolina prevented the eye wall from spinning into a more destructive storm by the time it arrived in New York.

"It never had that opportunity because North Carolina got in the way, dry air came across over Virginia and Maryland and got in the way, and although this was very low pressure, the reason why we could never let the guard down for New York City ... was because the pressure was low enough that at any time, if this storm decided to get its act together, it could have gone from a 60-70-80 miles per hour storm - it easily could have been a 110 (miles per hour) storm like it was in the Caribbean and like it was in the Bahamas."

Add to that the difficulties of having true accurate model data when it comes to hurricane forecasts.

“Real-time observations, like that collected by NOAA’s Hurricane Hunters, are put into these models to hopefully give a more accurate forecast. We are much more accurate on forecasting severe storms and their behavior for this very reason, the availability of observations," CNN meteorologist and weather producer Sarah Dillingham said. "These storms occur over land, allowing scientists to take measurements within those storms and use that data to run computer models. Think about a hurricane, over water, with no way to collect data except from above.

"Makes it difficult to see what is actually going on, right?"

Dillingham said dropsondes, instruments that are dropped from above and into these storms, are used to collect data inside hurricanes as they fall to the surface.

"This is helpful, but you are also trying to view the data it collected, track where it was in the storm, and at the same time determine what that means from a scientific perspective," she said. "Also, you may think, what about trying to send something up into the storm from below. In a hurricane? Good luck with that."

Dillingham said "the sparsity of real-time observations in tropical systems is what makes it so difficult to produce a more correct intensity forecast, and certainly makes it difficult to improve them."

"The track of these storms depends on atmospheric winds and surrounding storm systems, and we understand these factors much better, giving us a better handle on the 'steering' of these systems," she said. "This makes tracking more accurate overall. Things like RI, or rapid intensification, in tropical cyclones is just not fully understood yet, and until we can obtain that vital observational data within these storms - while they are over open, warm waters - we will struggle to model these kinds of processes.”

For that reason, Dillingham said Read's explanation of why they have trouble making these predictions is spot on.

And that's also why Read says the decisions to evacuate made by emergency managers and state and federal officials was the right one.

In every aspect of the storm except for wind speed, Read says, they got it right.

According to their initial analysis, the track forecast of the storm was 20% better than their five-year average. They do very well at predicting the path of a hurricane.

“We had storm surge flooding all the way up from the Carolinas into New England," Read said. We’ve had tremendous and tragic rainfall flooding. We’ve had loss of life from trees down well inland and the power outages.”

Hurricane forecasters admit their ability to foresee a storm’s strength is not much more today than it was 20 or 30 years ago.

According to the Hurricane Center’s initial analysis, “Irene exemplifies the state of the science.” They are pinning their future hopes on programs like the Hurricane Forecast Improvement Project. Scientists say they are seeing some promising results. This program uses high-resolution models and enhanced Doppler radars to measure the core of Hurricanes.

Forecasters say that three out of four times you will likely be asked to evacuate and you’ll coming back saying "Why did I leave?"

But that fourth time, if you don’t, Read says, you’ll wish you had.

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Filed under: Flooding • Hurricane Irene • Hurricanes • Weather
soundoff (639 Responses)
  1. Joe

    I think the forecaster's did their best, and the outcome was the best one for which we could hope. If the reverse had been true, and they hard forecast a Category 1 and yet it was a Cat3, people would be complaining that they didn't warn us of how bad it was going to be.

    August 30, 2011 at 1:14 pm | Report abuse |
    • Terri

      I agree, it is much wiser to predict the worst case scenerio than underestimate. People will complain regardless, that is much easier to take than lives lost if you go the other route. Some of us just love to nag.

      August 30, 2011 at 1:33 pm | Report abuse |
  2. MC

    Damage control article.

    August 30, 2011 at 1:15 pm | Report abuse |
  3. Keith

    its amazing that people are pitching a fit that the weather service didn't do their job and missed the mark. People this is MOTHER NATURE and there is absolutely no way to predict exactly where storms will go or what they will do. as they can and usually do change course at the last minute. I think this is a big deal because people are saying too much time and money was spent preparing for a storm that wasn't.....just you wait, next big storm that comes in more people will think nothing and stay behind, then wonder what the heck happened and then try and sue the weather people for being wrong (in their mind). It will turn into another boy crying wolf scenario

    August 30, 2011 at 1:15 pm | Report abuse |
    • Terri

      Some folks thrive on knocking people trying hard to save lives.

      August 30, 2011 at 1:37 pm | Report abuse |
  4. keeth in cali

    better inconvenienced and safe than dead

    August 30, 2011 at 1:15 pm | Report abuse |
  5. Marcus

    Our inability to forecast a 500 miles large phenomena should be food for thought for those who claim to understand the entire Earth's atmosphere (8,000 miles diameter), why it heats up, why it cools down and want to play with it too.

    August 30, 2011 at 1:16 pm | Report abuse |
    • A scientist

      You've got it completely backwards. It is almost always easier to predict broad trends of a large system than it is to predict the specifics of a subset of the system.

      For example, if baseball decided to switch to a slightly lighter ball, any intelligent physicist could easily predict whether the overall league-wide home run totals would go up or down. However, it would be much harder to predict how each individual player's home run totals would change (because of random year-to-year variations in hitting, and specifics about how each player's swing would be suited to the new ball), and impossible to predict exactly which days the extra home runs would be hit.

      August 30, 2011 at 3:53 pm | Report abuse |
  6. Gene

    Let's remember this when we choose whether to believe wild forecasts about global warming.

    August 30, 2011 at 1:17 pm | Report abuse |
    • Terri

      Only 2% of "scientists" disagree that man has played some role in the current climate change....but you keep listening to them, and check out who pays for their "studies".

      August 30, 2011 at 1:38 pm | Report abuse |
    • 40acres

      Exactly Gene....then maybe we too can be one of the dead.

      August 30, 2011 at 6:30 pm | Report abuse |
  7. Thar She Blowssssss

    Well, better that Irene couln't blow us as well as the forcasters said she would.

    August 30, 2011 at 1:18 pm | Report abuse |
  8. Mikhail

    Brilliant copy-editing once again from CNN. "Why Irene's forecast the missed mark"???? And right on the front page too in big letters!

    August 30, 2011 at 1:18 pm | Report abuse |
    • Adam

      How can a major news agency screw up a headline so badly?

      August 30, 2011 at 1:24 pm | Report abuse |
    • Dave

      As a web developer, I cringed, wonder how long before caption guy's back from lunch!

      August 30, 2011 at 1:25 pm | Report abuse |
  9. Scott

    I think the forecaster's did a good job however I think the media and Washington blew it up bigger then it needed to be like they always do.

    August 30, 2011 at 1:18 pm | Report abuse |
    • Joe

      I don't see how the media overblew this. From what the forecaster's said (and I don't fault them either), a major category 3 hurricane was about to hit the East Coast of the United States with the possibility to impact 100's of millions of people. To me, that is a new story worth covering.

      August 30, 2011 at 1:20 pm | Report abuse |
  10. kreamowheat

    You can predict storm intensity until you are blue in the face and there will still be idiots who do not heed the warnings and die; case in point with Irene, where people chose to surf or go exploring in the flood waters and die. Stupidity will always abound!

    August 30, 2011 at 1:19 pm | Report abuse |
  11. FutureWizard

    I'm glad we are alive to discuss this 🙂

    August 30, 2011 at 1:19 pm | Report abuse |
  12. BansheeFA

    I don't understand any thought other than a joyful one coming out of this storm being weaker than expected. Would it be nice if we could accurately predict the strength of storms? Yes. Am I, or should anyone be upset at the forecasters who's prediction was off. No.

    August 30, 2011 at 1:20 pm | Report abuse |
  13. Scott

    How Irene forecast missed the mark? How about for the same reason that corporate media spends so much time reporting on what celebrities had for lunch... Sensationalism sells.

    August 30, 2011 at 1:21 pm | Report abuse |
  14. phalen208

    I don't understand how they keep saying the storm was over-hyped or they missed the mark. What about the people who passed away because of the storm? Or the whole towns that we're flooded? or All the people without power right now? They kept saying that they wouldn't know until it got here what the force of it would be and what was to be expected IF it went this way or that way. Isn't it better to be prepared for the unexpected then not preparing for the exoected?

    August 30, 2011 at 1:21 pm | Report abuse |
    • Lee Rutter from Houston

      I think what got a lot of folks upset was when the media chooses to stand on a beach and lean to one side and shout as loud as they can and talk about the vast amount of destruction that is going to happen. You have to realize, the mayors and governors were calmly telling people the truth... there will be flooding, downed lines and electricity may be out. They told the people if you are in low areas, get to higher ground. The media just went crazy about all kinds of scenarios to fill air time. People are wanting to know so much that the forecasters can't predict until the hurricane hits, but sometimes the media takes on more than they can chew and gives off misinformation. Example... the media at one time said "Wow, this hurricane is moving really slowly" when in fact it was moving at 12.5mph. Come on! For a storm or hurricane, that's fast! And also, at the very beginning, the bottom half of the hurricane had disappeared and the weather channel immediately zoomed in to hide the fact the bottom part was gone. I told my wife and she told me I was a liar, that no way could the bottom half of the hurricane disappear. I go to the bedroom fifteen minutes later and pull up CNN.com and there was an article on the front page that commented the bottom half was gone!!! I know, CNN is part of the media and they did report the truth in that instance.

      August 30, 2011 at 3:01 pm | Report abuse |
  15. shared_gum

    I am not mad at the forecasters. Exercising caution is fine. I live in Maryland near Washington DC, and my family slept in the basement. About 200 yards down from our house, two huge trees were uprooted and fell on two different houses. A parked passenger car was smashed. This could have been my house and my car. Nothing happened to me, but it was good to be cautious.

    August 30, 2011 at 1:22 pm | Report abuse |
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