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. Jeff

    because they are lame as*ses

    August 30, 2011 at 1:23 pm | Report abuse |
  2. josh

    id rather be ready for a bad storm and be ready for it. then have them say its a baby storm and it be massive and people not even be close to being ready for it.. so all and all their methods are fine plan for the worst hope for the best! But as we all know we do live in the USA and everythign boils down to $$$ no matter what the case or the questions is/are. weather brings in RATINGS! which equals $$$$$$$$$$$$$$$$$$$$$$$

    August 30, 2011 at 1:23 pm | Report abuse |
  3. Cradle

    I'd much rather they over-predict the intensity of the storms, forcing people to err on the side of caution when preparing for them.

    August 30, 2011 at 1:23 pm | Report abuse |
    • GamblerATX

      Agreed. The prediction of the path is more important in my opinion. Assume a storm will be destructive. Plan for the worst. Hope for the best.

      August 30, 2011 at 1:29 pm | Report abuse |
  4. Joe

    Do those of you complaining even hear yourself? 'News media: If you report predictions of cataclysmic death and destruction, there better well be cataclysmic death and destruction, or I am gonna be really upset' How about count your blessings?

    August 30, 2011 at 1:23 pm | Report abuse |
    • 40acres

      Well said Joe.

      August 30, 2011 at 6:58 pm | Report abuse |
  5. Rod C. Venger

    This isn't brain surgery. Hurricanes are powered by warm waters. Warmer water and moisture equals more powerful storms. Hurricanes push huge cold fronts ahead of them and when they reach land, they invariably lose much of their power. A Cat 5 on the water will drop to a Cat 3 when it moves over land. A Cat 3 will drop to a Cat 1 or a tropical storm after it reaches land. If it goes back over warm water, it'll often power back up. No mystery here at all and it's best to assume the worst case, not the best case, scenario.

    August 30, 2011 at 1:23 pm | Report abuse |
    • cyclobrown

      look what a Cat 3 did in NOLA.

      August 30, 2011 at 1:27 pm | Report abuse |
  6. Ken

    I love all of the second-guessing, backseat-driving, Monday-morning-quaterbacking know-it-alls out there. If you can do better, start predicting storms professionally! Good luck with the advanced chemistry, natural science, climate science, non-linear dynamics, and everything else that goes into being a good meteorologist. I'm sure you can do it, once you quit your job as a truck driver/ insurance salesman/ Wal-Mart greeter/ housewife.

    August 30, 2011 at 1:23 pm | Report abuse |
    • cyclobrown

      c'mon. most look at a hemispheric satellite map, calculate speed, annnd its time for coffee. if you dont get a science degree you might as well have saved the money

      August 30, 2011 at 1:34 pm | Report abuse |
    • Steve

      Tee hee

      August 30, 2011 at 1:44 pm | Report abuse |
  7. aNN

    Breaking News: Peta was summoned to the Jersey Shore attempting to assist a beached Whale, turns out it was Chris Christie.

    August 30, 2011 at 1:23 pm | Report abuse |
  8. Jan

    Maybe you should tell the people in Virginia and North Carolina that they are lame as*ses. Especially those that are still withou power and some who lost their homes. I'm sure they would agree with you. What is wrong with you?

    August 30, 2011 at 1:24 pm | Report abuse |
  9. susan

    The mercy of our Lord saved us from a horrible storm. Only Jesus can calm the storms. Also the storms of peoples lives. I did pray a lot and learned a lesson Trust in the Lord. And be thankful for each new day that we can share with love ones.
    Every day is a Present!!!!
    Thank you Jesus!

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

      Reminds me of a joke: A guy is stranded in the ocean and is waiting for God to save him. A boat comes by and he says no, I'm waiting for God to save me. Then a helicopter comes by and he says no, I'm waiting for God to save me. Finally another boat comes by and he again says no, I'm sure God will save me. Then he dies and goes to heaven. He asks God, "Why didn't you save me?" God says, "What are you talking about? I sent you two boats and a helicopter!"

      August 30, 2011 at 1:36 pm | Report abuse |
  10. rjb1971

    Ask all the people dealing with the flooding and ruined lives in the northeast if it missed the mark. It seems like people are annoyed that it wasnt worse.

    August 30, 2011 at 1:24 pm | Report abuse |
  11. Noname500

    I am confused. Shouldn't we be happy that the forecast was wrong. I mean this was the best case scenary. I personally am glad it was weaker than everyone though. They erred on the side of caution, and it turned out better than we thought.

    August 30, 2011 at 1:24 pm | Report abuse |
  12. Ct

    Because, the worse the problem the better the ratings. I'm just glad OBAMA was able to come off of vacation to lead his nation against his Katrina.

    August 30, 2011 at 1:24 pm | Report abuse |
  13. AK

    Could someone please fix the botched headline on the CNN main page? It's just embarrassing that no one bothers to proof this stuff. If you need a proofreader, email me.

    August 30, 2011 at 1:25 pm | Report abuse |
  14. ironsides

    "Hurricane forecasters got the path right, but say they were way off on Irene's intensity. They admit their ability to predict storm strength isn't better than 20 years ago."

    AND probably never will be better once the republicans disband NOAA as a gov agency.

    August 30, 2011 at 1:25 pm | Report abuse |
  15. Rob

    What a load of crap....the reason they pumped up this storm was because they never want to underguesstimate....calling for some bad weather and having the actual weather be far worse can cost people lives....overestimating only causes financial's the same reason they will call for 12" of snow in the winter only to find 6" at most actually fall....

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