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Posted at 12:50 PM ET, 11/18/2010

Hurricane season in 2010 made history

By Greg Postel

Third most active season in modern times

2010 Hurricane Season Forecasts
Named Storms
Hurricanes
Major Hurricanes
AccuWeather - Joe Bastardi
15
5
2 or 3
Colorado State University
15
8
4
Tropical Storm Risk Inc.
16
8-9
4
WeatherBug
12-17
6-9
3-4
NOAA
14-23
8-14
3-7
Forecast Average
16
8
4
 
2010 Season Actuals (to date)
19
12
5
Long-term Average
10
6
2

Long-range forecasts made last spring for the 2010 Atlantic hurricane season almost unanimously predicted lots of storms. Though they generally underforecast how many we would actually observe, they were right it would be an active season.

Our summary of these forecasts, posted in May, essentially outlined the prevailing wisdom that this year would be really, really active - much more so than recent historical averages were showing. The table above shows pre-season predictions from some well-known prognosticators, along with the 2010 numbers so far.

The 2010 statistics not only eclipsed the forecasts in each of these categories, they made history in passing them by (and the season technically has about two more weeks). In remarkable fashion, the ocean-atmosphere interplay throughout the tropics in 2010 allowed for a hyper-production of cyclones rarely matched in modern times. Only 2 seasons since 1944 recorded more named storms: 1995 (19) and 2005 (28).

Two significant reasons why this year's numbers were so high are rooted in the oceanic conditions in both the Atlantic and Pacific Basins.

Sea surface temperatures (SSTs) in the Atlantic were warmer than average throughout the tropics, and the phase of ENSO (El Nino-Southern Oscillation) in the Pacific slipped into the La Nina category prior to the start of summer. Both factors are consistent with an increase in Atlantic hurricane frequency. Warm SSTs can provide more energy for storms to develop and maintain themselves, while the La Nina condition present in the Pacific is often associated with a seasonal reduction in destructive wind shear over the Atlantic.

Yet the 2010 season may be remembered more for the 'near misses' than for making the all-time active list. The numbers here are astonishing. Twelve hurricanes and no U.S. landfalls? It's never happened before in our observational record going back to the late 1800s. Only one tropical storm landfall (Bonnie) out of 19 candidates? Come on.

The common perception among the tropical community is that the U.S. coastline was lucky. I would argue that we were instead fortunate. There was a reason these systems avoided the U.S. like the plague. And luck had nothing to do with it.

The steering currents for the 2010 storms repeatedly spared the U.S. from a landfall. The underlying shape of the atmosphere during the heart of the season featured upper-level high pressure systems over the Central Atlantic and over the Southern Plains (shaded in red in the picture below).

tropics-2010-500mb-heights.jpg
Map of average pressure (or heights) at an altitude of about 18,000 feet (500 mb) during the 2010 hurricane season

The clockwise flow around the core of these systems often led to a high-altitude southerly wind just east of North America and upper-level northwesterly or northerly flow over the Gulf of Mexico. The image below shows a time-averaged view of the anomalous winds aloft associated with these highs.

tropics-2010-vectors.jpg
Average wind vectors (arrows showing direction of wind) at an altitude of about 18000 feet (or 500 mb) during this year's (2010) hurricane season.

Many of this year's tropical cyclones that migrated westward across the tropical Atlantic found a 'soft spot' in the upper flow over the eastern Atlantic, between the two high pressure systems in the 75W to 55W longitude band, where the winds aloft were often directed northward. The steering currents over this sector of the Atlantic, rarely aimed at North America, effectively shoved approaching storms toward the north and back out to sea. Further to the west over the Gulf of Mexico, the frequently observed northerly flow blocked storms that formed in the Caribbean from turning northward in time to cross the U.S. Gulf Coast.

The map below shows these two distinct track clusters quite well, with one set recurving northward over the western Atlantic and another group traveling west or west-northwestward over the Caribbean.

2010-storm-tracks.jpg
Storm tracks during the 2010 hurricane season. Courtesy Unisys Weather

This year we were fortunate ... not lucky ... that the steering currents did not direct storms toward the U.S. coast like they did, for example, in 2004. That year the flow aloft often featured an easterly component over the Southwest Atlantic and a southerly or southwesterly wind over the Gulf of Mexico, nearly opposite to what we saw this year.

tropics-2004-vectors.jpg
Wind vectors (arrows showing direction of wind) at an altitude of about 18000 feet (or 500 mb) during the 2004 hurricane season.

The wind patterns shown above during the core of the 2004 season paved the way for numerous destructive landfalls along Florida's Atlantic and Gulf coastline, including Charley (Category 4), Frances (Category 2), Ivan (Category 3), and Jeanne (Category 3).

Looking ahead, the global circulation -with all of its interrelated parts- will likely not be so favorably configured next season. The governing dynamics will probably put the centers of action (e.g., the upper-level high pressure systems) in another place with a different shape and intensity, and thereby shift the longitude band in which recurvature (the northward turn) takes place. We can only hope that this also means that the large-scale conditions for hurricane development are not so hospitable.

By Greg Postel  | November 18, 2010; 12:50 PM ET
Categories:  Latest, Tropical Weather  
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Comments

Just for comparison here is the NOAA forecast on May 27, 2010:

a 70 percent probability of the following ranges:

* 14 to 23 Named Storms
* 8 to 14 Hurricanes
* 3 to 7 could be Major Hurricanes

Posted by: dsmflood_guy | November 18, 2010 1:27 PM | Report abuse

@dsmflood_guy

Thanks for adding that! I'm going to place these numbers in the table.

Posted by: Jason-CapitalWeatherGang | November 18, 2010 1:45 PM | Report abuse

Given that most of those storms were fish hurricanes, the raw number (19) is hardly "historical", except to datakeepers. In the days before weather technology was so sophisticated, a lot of these storms would have gone unnoticed, save by vessels unfortunate enough to be in their path and many of these storms would never have been officially recorded.

The Tomas-induced intensified cholera epidemic in Haiti was dire. Otherwise, 2010 was (thankfully!), a hurricane yawner.

Posted by: JerryFloyd1 | November 18, 2010 1:50 PM | Report abuse

I am still waiting for TRAVELERS INSURANCE to make proper settlement on damages caused to my home and property as the result of a storm in JULY of 2010. DO NOT BUY TRAVELERS insurance! They are Thieves!!

Posted by: 10bestfan | November 18, 2010 2:56 PM | Report abuse

Hi JerryFloyd1

I disagree. It was indeed a rare year, and the recent records aren't as bad as you think. Please see Chris Landsea's (formerly of HRD, now at NHC) construction of historical hurricane-track datasets. His excellent work takes an exceedingly thorough look at all available data in order to re-analyze hurricane history.

And with all due respect, 2010 was no yawner. Just ask any hurricane scientist/forecaster at NHC who's job is to protect life and property.

greg

Posted by: gregpostel | November 18, 2010 3:18 PM | Report abuse


I really don't count hurricanes which don't strike land. Most of these were duds and if any ships were caught, shame on them.


Posted by: mortified469 | November 18, 2010 5:15 PM | Report abuse

Greg, thanks for responding, by "yawner" I meant the news media and its consumers didn't have much opportunity for hurricane coverage melodrama, such in past years. E.g., the newscaster standing in the high wind and rain and/or in front of the raging surf, risking their (and their cameraperson's) physical well being for the ratings game.

Re: the claim that this was an extraordinary year for the total number of storms, this is based on historical data that's at best about 100 years old? I'm sure there were many fish hurricanes and/or localized storms in past centuries that weren't recorded. Important, I think, to maintain a historical perspective. The book "Hurricanes and the Middle Atlantic" is a real eye-opener in this regard, as are the shipwrecks that appear from time to time on the Outer Banks.

We live in an era when everyone wants to set records (and I confess I am so hoping we get another 13" of snow at DCA before the end of this CY to push the yearly total above 50"). But, as noted, history can be very chastening.

Posted by: JerryFloyd1 | November 18, 2010 5:48 PM | Report abuse

To give the public the impression that the science supports a precision that allows for one number for these forecasts significantly discredits the Meteorological Community. I hope CSU, Accuweather, can see the folly of their ways. Don't you feel good that your tax money really provided the best forecast! I do.
Bob Landis
Former Deputy Director NWS,
Former Director World Weather Watch

Posted by: landisrc1 | November 18, 2010 6:04 PM | Report abuse

Hi JerryFloyd1

yes, yep, and agreed. :)


greg

Posted by: gregpostel | November 18, 2010 6:04 PM | Report abuse

There was another important factor, the presence of large amounts of Saharan air in the Atlantic. This was a major factor in weakening virtually every hurricane this year.

Posted by: peterroach | November 18, 2010 6:21 PM | Report abuse

Hi landisrc1

Yes. If there's one thing science is sure of, it's that it's not literally sure about most everything. All we can do is submit a best estimate with error bounds. Unfortunately, that's too much uncertainty for many people to handle. Public demand has outrun our capabilities.

greg

Posted by: gregpostel | November 18, 2010 6:21 PM | Report abuse

Hi peterroach

Do you mean that the SAL (Saharan Air Layer) was a factor in our near misses ? Perhaps ... but probably only to the degree that the weakening by SAL inhalation changed the steering layer *to* one that recurves. Given that SAL interactions weaken storms, and with steering currents for these weakened storms then coming from lower altitudes, this argument assumes the mid/upper-level flow would have driven the storms onshore. It's not clear how often that happened.

greg

Posted by: gregpostel | November 18, 2010 6:47 PM | Report abuse

landisrc1

Bob, right on with regard to the uncertainty conveyed with the seasonal tropical storm predictions

It's unfortunate, however, that the NWS talks a lot, but does not meaningful act to change the folly of its ways, namely a public product suite that is primarily single valued.

Greg, a number of studies (including one by Bob Ryan) show the public gets it about uncertainty. The NWS, however, is negligent in my opinion for not providing the readily available information on uncertainty.

Posted by: SteveT-CapitalWeatherGang | November 18, 2010 7:11 PM | Report abuse

Hi SteveT-CapitalWeatherGang

"get it" ... as you show, they apparently do. I instead wrote "handle it". Totally different.

greg

Posted by: gregpostel | November 18, 2010 7:59 PM | Report abuse

@BOB LANDIS

I am not sure what you are driving at in your post. You mention CSU accu Blunder and the "folly of their ways"...(I presume this also applies to a company such as tropical storm Risk as well?).

are you saying that making ANY seasonal forecastng is wrong and cannot be done with any skill?

If so then clearly that is not correct.

IF on the other hand you are saying that the forecasts for Landfall probabilities
made back in MAY - JUNE b Dr Gray et al and Accu wx (ie JB) were once again terribnly wrong then you are 100% correct.

BUT, that being said accu wx's Hurricane forecast are routinely viewed with scorn and snickers... as year after year they are the worst ones out there.

Their call for 6-7 US landfall Hurricanes
or which 2 or 3 would be Intense Hurricanes was Typical.

Dr Gray use of statistical probabilities in making his US Landfall Hurricane CHANCE forecast is Just as bad.

But that does NOT mean it cannot be done.

This year at WXRISK.com I went for 1 or 2 US landfalling TC and NO Hurricane (and 21 nameds TC.)

I did not make THAT forecast just to be contradictory. The SYNOPTIC pattern in June showed that for the Summer /early autumn the SE US ridge and the Mid Atlantic Trough would ensure few if any US landfalling 'canes.

My point is that one CAN make a Forecast about US landfall hurricanes. But the headline "Lots of Hurricane but few to strike US coast" does not sell papers.

Gr Gray's statistitical Method will almost ALWAYS fail because TC do make landfall based on synoptic scale patterns NOT becuase of Statisitics.

Accu-wx's Landfall Hurricanes forecasts are usually way off because with them its about Hype and not seeing the REAL pattern.

Posted by: wxrisk | November 18, 2010 8:17 PM | Report abuse

peterroach


The SAL had NOTHING to do with WHY none of the 12 Hurricanes in the 2010 made US landfall.

The SAL? are you kidding me? the SAL caused TC to turn out to sea?

the SAL certainly had NO impact in the western Carib or the Gulf.

of the 12 Hurricanes we had FOUR category 4 'canes and 1 category 3.

Hard to argue SAL when you see 5 of 12 hurricanes in 2010 were IH

Posted by: wxrisk | November 18, 2010 8:26 PM | Report abuse

Hi wxrisk

I agree with your theme that the dryness of the SAL did not "cause" hurricanes to recurve. At least not directly. But there could be an indirect relationship there, to the extent that the steering layers are changed in response to SAL-induced TC weakening. But there again, I agree with you that I haven't seen evidence for that this year.

But maybe peterroach was suggesting that there were tropical cyclones that might have hit the U.S. had they not disintegrated entirely. Again, it's hard to know. Coulda/Woulda. But he/she is right that the SAL (or at least excursions of nontropical RHs) were quite involved in modulating TC development this year.

let's keep it light-hearted :)

greg

Posted by: gregpostel | November 18, 2010 10:17 PM | Report abuse

My takeaway is there are lots of variables. I certainly was surprised by the way some storms strengthened against the odds (e.g. Julia) but also saw total duds (e.g. gaston) despite having a forecast for major hurricane status.

Question for wxrisk, how persistent are the synoptic patterns and if they change, how predictable is the change? I tend to agree that purely statistical approaches are not very useful.

Posted by: eric654 | November 18, 2010 11:22 PM | Report abuse

One notable effect of the failure of any tropical storms to impact this area: the rather unusual dry spell our area endured during much of September.

Normally we have one or two tropical systems which hit or brush by us during the Cape Verde season, accounting for two to eight inches of rainfall around here during the period. This year...not a thing! The big rain storm which hit us at the end of the month was mainly a subtropical/extratropical event with maybe a bit of tropical moisture thrown in.

Posted by: Bombo47jea | November 19, 2010 12:42 AM | Report abuse

re @Bob Landis
I am in favor of Seasonal Forecasts,but lets not imply that the science permits the forecast of a precise number versus a range. I hope we are not providing a single number just because the public wants it! My discussions with the public indicate they DO NOT UNDERSTAND the error limits on longer term forecasts. For many people, whatever error understanding they have for the 24 hour forecast is extrapolated on out to longer term forecasts that infer a precision that is not supported. Bob

Posted by: landisrc1 | November 19, 2010 6:37 AM | Report abuse

re @Bob Landis
I am in favor of Seasonal Forecasts,but lets not imply that the science permits the forecast of a precise number versus a range. I hope we are not providing a single number just because the public wants it! My discussions with the public indicate they DO NOT UNDERSTAND the error limits on longer term forecasts. For many people, whatever error understanding they have for the 24 hour forecast is extrapolated on out to longer term forecasts that infer a precision that is not supported. Bob

Posted by: landisrc1 | November 19, 2010 6:38 AM | Report abuse

Greg,
Correction needed: "Only one tropical storm landfall (Bonnie) out of 19 candidates? Come on."

Make that two.

Perhaps you forgot about Hermine, our rapid spin-up which crashed through a population of more than 250,000 in Deep South Texas?
http://weather.gov/rgv/?n=2010event_hermineindex

While Hermine's "landfall" location was just south of the border, we suspect that the storm intensified as it moved into Cameron and Willacy County. Texas.

And, Cameron County, TX, was the only location in the United States impacted by three cyclones in 2010: Alex (a tropical storm for the county and a hurricane 100 miles south), TD #2, and T.S. Hermine.

I can assure you that the community known as the Rio Grande Valley was ready for a "big" season, and between these three cyclones, as well as the resultant flood situation on the Rio Grande/Rio Bravo and associated waterways, 2010 won't be forgotten soon.
http://weather.gov/rgv/?n=2010event_julyriograndeflood

The best news is while there were multiple impacts, the area escaped a big direct hit (Alex). With only one indirect fatality during the period of flood which followed Alex and TD #2.

Posted by: wxdancer | November 22, 2010 10:06 AM | Report abuse

Hi wxdancer

Incorrect. According to NHC's storm summary and official season wrapup, Hermine was a 60-knot tropical storm at landfall.

Here's an excerpt from Lixion Avila's official tropical cyclone report on Hermine. You can find it at http://www.nhc.noaa.gov/2010atlan.shtml

Hermine made landfall on the coast of northeastern Mexico about 25 n mi south of Brownsville, Texas at its peak intensity of 60 knots and a minimum pressure of 989 mb at 0200 UTC 7 September.

greg

Posted by: gregpostel | November 30, 2010 5:19 PM | Report abuse

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