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Posted at 11:45 AM ET, 08/ 5/2010

NOAA says active hurricane season still likely

By Greg Postel

* Hot; T'storms today? Full Forecast | Hurricane Tracking Center *
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An updated hurricane season forecast issued by the National Oceanic and Atmospheric Administration today continues to call for a very active season in the Atlantic Basin, and possibly one of the more active ones on record. NOAA forecasters expect a 90% chance of an above-normal season, with a 70% chance of 14-20 named storms in total (including the three so far), 8-12 of which are predicted to be hurricanes and 4-6 of these major hurricanes (Category 3 or higher).


Satellite image from this morning shows a relatively quiet tropical Atlantic, with the remnants of Tropical Storm Colin spinning north of the Virgin Islands, and a tropical wave over the southwestern Carribean Sea. But forecasters expect the tropical season to eventually pick up steam. Image credit: NOAA

"There remains a high likelihood that the season could be very active, with the potential of being one of the more active on record," said Gerry Bell in a NOAA release. Bell is lead seasonal hurricane forecaster at NOAA's Climate Prediction Center.

The only real difference between this update and the outlook issued in May is that the upper end of the ranges have been lowered slightly, only because activity so far has not quite matched the maximum potential allowed for in earlier forecasts.

The forecast reasoning is unchanged: La Nina conditions (cooler-than-average waters in the equatorial Pacific Ocean) continue the expectation that wind shear over the Atlantic Ocean should be, in the big picture, relatively weak. Also, waters in the tropical Atlantic and Carribbean Sea remain warm, and we are still in the midst of a multi-decadal uptick in hurricane activity.

In its May 27 forecast, NOAA projected a 70% chance of 14-23 named storms (8-14 hurricanes and 3-7 major hurricanes) based on reasoning similar to that used in this latest outlook:

  • An expectation of an upper air flow conducive for storm development (relatively weak wind shear) during the late summer and fall over the regions where tropical cyclones tend to develop -- largely in association with the collapse of El Nino conditions (warmer-than-average waters in the equatorial Pacific) earlier this year.
  • Unusually warm waters in the tropical Atlantic and Caribbean Sea.
  • Continuation of the multi-decadal increase in hurricane frequency that began in the mid-1990s.

As we now approach the meat of the hurricane season (which peaks in mid-September), we shift our attention away from predicting how the season as a whole might shape up based on parameters that tend to vary from season to season, and instead focus on intraseasonal variables that impact the likelihood for storm development on a week-to-week basis.

In other words, the table has been set, so to speak, by the seasonally varying parameters. Now, it's time to forecast the "weather" over the main development regions -- the details of which are critically important to whether any single storm will form and strengthen.

By Greg Postel  | August 5, 2010; 11:45 AM ET
Categories:  Tropical Weather  
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Comments

based on their past "the sky is falling" record, I"ll just wait and see for myself.

Posted by: silencedogoodreturns | August 5, 2010 11:58 AM | Report abuse

Hi silencedogoodreturns,

there's no "the sky is falling" in the outlook. It's just science.

Sometimes some media spins might make it seem like it, but NOAA is just giving us their best scientific assessment based on facts.


greg

Posted by: gregpostel | August 5, 2010 12:05 PM | Report abuse

saw a commercial from the Red Cross this morning asking for donations based on this update.

Posted by: SPS1 | August 5, 2010 12:59 PM | Report abuse

Why do these guys get to revise their forecast? I call BS on that.

Posted by: Tom8 | August 5, 2010 1:21 PM | Report abuse

@Tom8,
Any long range forecast should be subject to revision as needed, as long as the original forecast is not hidden so as to make the revision seem to be the only forecast which has been made. That really would be BS - misleading, and cheating professionals in the field out of the opportunity to increase their understanding of the factors they use for their predictions.
The atmosphere and seas are not static, and one change leads to another. I'm tired of the assumption that if a prediction changes, whether for weather or the economy, it means that the first prediction was done sloppily or with an ax to grind. While both of those are possible, circumstances and thus data do change, sometimes causing the forecast to need revision.
Specifically on weather, anyone who has watched this blog for a few months should be well aware of the need to change a forecast (particularly in this region of the country), and the fact that given even the best forecast, on-the-ground reality can differ from what one expects.

Posted by: fsd50 | August 5, 2010 1:41 PM | Report abuse

I see Fox News is distorting the truth again. Here's their headline:

"Hurricane Season Promises a Rough Ride, Weather Agency Says"


Total lie. They never said the season "promised" a thing. There are no guarantees. Only estimations.

It figures, it's FOX.

Posted by: gregpostel | August 5, 2010 2:16 PM | Report abuse

I have been reading the Capital Weather Gang for several months and want to congratulate you all on clarity.
This has been one of the warmer summers in memory and accurate predictions of highs are important to me for health reasons. I am 75, have diabetes, and tend to get rashes at very high temperatures and humidity. So I need good weather reports in order to plan gardening, errands, etc.
One little nit-pick: I am not used to seeing the word multi-decadal and think that multi-decade is ok. Anyhow, thanks for all the good work.

Posted by: lmuise1 | August 5, 2010 8:01 PM | Report abuse

Hi lmuise1,

I'll do my best for ya.

thanks for the kind words to Capital Weather Gang.

greg

Posted by: gregpostel | August 5, 2010 8:20 PM | Report abuse

@lmuise1

Many thanks for the nice words. We're glad you find our weather coverage helpful.

Posted by: CapitalWeatherGang | August 5, 2010 8:20 PM | Report abuse

Hi, Greg, I write this as a fellow scientist (but not at all in the weather industry or anything related), and I'm afraid that I do have to call a bit of B.S. on the NOAA (and others') hurricane predictions after 1/3 of the hurricane season has passed. I mean, let's face it: It's no longer quite the same "prediction" anymore when we've already had 1/3 of the season go by -- you've already removed a certain proportion of possible storms through the passage of time. Whether they occurred or not should not be part of one's "predictions" for the whole season. That's just silly.

More important, though, is my question regarding how accurate NOAA's predictions really are. Have you ever analyzed NOAA's predictions given immediately before each hurricane season (e.g. the May 27 prediction) and seen how well their predictions stood up? I'm rather curious about it.

Moreover, in its May 27 forecast, NOAA gave a 70% chance of there being 14-23 named storms (i.e. TS's and up). This is absurd: giving a percentage chance AND giving a ridiculously wide range! Let me ask you: How many times over the past 10 years have there been 14-23 named storms in one year? If this number is anywhere over 50%, I don't think betting on a 70% chance of having 14-23 named storms is much of a "prediction".

Like I said, though, my biggest beef is that I haven't seen anyone examine how accurate NOAA's forecasts are for Atlantic hurricane season, taking into account whether NOAA is making an easy prediction (e.g. 60% chance of having 6-18 named storms) or a tough one (e.g. 90% chance of having 8-14 named storms). Over the past few years (really, since Katrina), we've been told over and over to expect a bad hurricane season. Some years, they're right, and some years, they're wrong. Essentially, I don't see any predictive validity here -- and I've paid close attention since I've been living in the Southeast. Thanks in advance for looking into these twin issues (accuracy combined with specificity of predictions).

Posted by: rlalumiere | August 5, 2010 9:16 PM | Report abuse

Hi rlalumiere,

I wrote a blog about the accuracy and utility of seasonal hurricane forecasts last Spring. There's some skill there, but one has to understand what they're saying in order to extract that skill. Unfortunately, many media outlets just don't relay the true essence of the forecasts. Nor do they appreciate that the science can't be taken out of context with the uncertainty removed.

As you say:
It's no longer quite the same "prediction" anymore when we've already had 1/3 of the season go by -- you've already removed a certain proportion of possible storms through the passage of time.

Righto, it's not the same forecast. It's a different one. And with the hurricane season still in its 'early' stages, why not put a forecast out for the rest of the way? (the historical frequency chart doesn't really pick up until mid August ... and the heart of it goes all the way through early October). So it really hasn't gotten into swing yet, in a historical view.

You say:
Let me ask you: How many times over the past 10 years have there been 14-23 named storms in one year? If this number is anywhere over 50%, I don't think betting on a 70% chance of having 14-23 named storms is much of a "prediction".

In the last 10 years there have been 5 seasons with 14-23 named storms. But keep reading. Of those 5, three were at the bottom of that range (15 or 16), one was still less than half way up that scale (18), and only ONE was off the charts (2005). The fact that the mean of their range has only been exceeded once in the last 10 years (by the year that was the most active on record) tells me that this is quite an astounding prediction ! But keep reading. In addition, pulling these last 10 years out of the hat is a biased sampling. The last 10 years has been among the most active decades on record.

So to me, a 70% chance of 14-23 storms is one that says they think it's likely to be a really *really* busy year in a historical context. Isn't that worth something ?

Whether it'll verify or not ... that's another story.

greg

Posted by: gregpostel | August 5, 2010 10:15 PM | Report abuse

The continued prediction of an extremely active hurricane season, affirmed despite so far unimpressive activity, is notable. Furthermore the predicted track for Tropical Storm Colin hints at trouble to come. Frequently, hurricanes that occur within several weeks of each other, moving through the same general geographic area--in this case the western Atlantic--tend to take roughly parallel tracks. The upshot: one or more of the major hurricanes to come may parallel Colin by tracking along the Atlantic Seaboard.

Posted by: ricschwartz | August 6, 2010 1:24 AM | Report abuse

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