Hurricane Julia explodes — Atlantic has two coincident Category 4 hurricanes, very rare

UPDATE 5 AM AST: Second time in 100-years two coincident Category 4’s in the Atlantic…together, Igor and Julia have the highest coincident intensities on record.

Two major hurricanes exist simultaneously in the North Atlantic, a rare occurrence.  With the current intensities (110 knots +) of Julia and Igor, this has only happened 3-times in the past 60-years:  1950 [Dog & Easy], 1958 [Helene & Ilsa], and 1999 [Floyd & Gert].  But Igor and Julia are both very powerful major hurricanes, they are Category 4’s.

  • Unprecedented:  in our North Atlantic historical records, the forecast intensities of Igor and Julia during the next 12-24 hours will be unprecedented for coincident storms.  The only other time (we know of) coincident Category 4+ hurricanes occurred was in 1926 with Hurricane #4 and the Great Miami Hurricane (September 26 at 06:00 UTC).
  • More:  At 115 knots +, Hurricane Julia is the most intense storm that far in the Eastern Atlantic [-31.8W] joining other major hurricane east of -35W including Frances 1980 and Fred 2009.
  • Early morning September 15: 12-hour forecasts indicate a maximum intensity of 120 knots for Julia and 130 knots for Igor. Two coincident Category 4 hurricanes have not occurred since 1950.  The only occurrence since 1900 happened on September 15, 1926 at 06Z with Hurricane 4 [115 knots] and the Great Miami Hurricane [120 knots].
  • Thus, Igor and Julia will attain have attained coincident intensities that are unprecedented:  Igor:  130 knots & Julia: 115 knots.

Hurricane Julia has rapidly intensified during the morning hours of September 15, blowing up to Category 3 + (110 knots).  Meanwhile, closer to the USA mainland, Igor was packing 135 knot winds, just the smallest of margins weaker than Category 5.  Need 136 knots, but the NHC issues advisories in increments of 5 knots.  If Igor does not break the Category 5 plateau, it is possible a post-season re-analysis will bump the storm into the most extreme Saffir-Simpson category.

ACE has really picked up:  90 as of 00Z September 15… [note the Western Pacific is 83% below normal].

Coincident major hurricanes (96 knots +) in the Atlantic basin have not occurred very often since 1950.  To ferret out the occurrences, we need to go into the best-track database.

From the HURDAT best-track database, which I have put into a easily digestible form here:  Atlantic storm listing, it is trivial with a quick UNIX/Linux command prompt:

cat hurdat_1850_2009 | awk ‘($1 >= 1950 && $8 >= 100) {print $4}’ | sort -n -k 1,1 | uniq -d

1950090406 – 1950090518

1951090712 – 1951090800

1955091806 – 1955091900

1958092618 – 1958092800

1961091112 – 1961091200

1964090918 – 1964091000

1969081806 – 1999091500

1999091506 – 1999091512

But Julia is at 110 knots and Igor at 135 knots.  Let’s then see the occurrences of 110 knots+ for two hurricanes:







Only 6 time-instances in the best-track since 1950!

Here are the particulars for those events:

YEAR, #, BASIN, DATE, STAGE, LAT, LON, Wind Speed (knots)

1999 09  NA 1999091506 TS  28.20  -78.50 110

1999 10  NA 1999091506 TS  17.40  -47.90 110

1958 08  NA 1958092700 TS  31.70  -78.10 110

1958 09  NA 1958092700 TS  21.40  -61.20 115

1958 08  NA 1958092706 TS  32.40  -78.50 110

1958 09  NA 1958092706 TS  21.90  -61.30 110

1950 03  NA 1950090500 ET 39.70  -56.80 55

1950 04  NA 1950090500 TS  23.40  -67.70 140

1950 05  NA 1950090500 TS  27.90  -83.10 110

1950 03  NA 1950090418 TS  38.40  -58.10 65

1950 04  NA 1950090418 TS  22.90  -67.20 135

1950 05  NA 1950090418 TS  28.00  -83.80 110

1950 03  NA 1950090412 TS  37.80  -58.80 70

1950 04  NA 1950090412 TS  22.60  -66.80 135

1950 05  NA 1950090412 TS  27.40  -83.20 110

Early September 15, Julia was at 110 knots, Igor at 135 knots, and Karl at 40 knots.


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Is this ‘Unbelievable’ because it has happened 3 times in the last 50 years (and who knows how many more times prior to that?)

where’s my plywood?
oh wait Im in SF
Cool Ryan you must be stoked!
ryan: [i’m in Monterey enjoying the same fog banks as you]

It’s certainly been windy in the UK overnight. One of the plastic chairs on my patio was on its side this morning.

And each one of these storms sucks heat out of the ocean and sends it on its way.
Hmmm…let’s hope they are fish storms but I would stack an extra cord of firewood on the off chance that absent heat plus La Nina equals one very, very cold winter.


In the SH the Polar front jet has meandered up to around 40s a big antarctic blast into the mid latitudes.
ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…

Old Goat

Something else for the warmista to blame on AGW…

Ryan (excitedly) said;
“Unbelievable: in our North Atlantic historical records, the forecast intensities of Igor and Julia during the next 12-24 hours will be unprecedented for coincident storms. The only time coincident Category 4+ occurred was in 1926 with Hurricane #4 and the Great Miami Hurricane (September 26 at 06:00 UTC).”
You forgot to insert the words ‘short’ before the phrase ‘North Atlantic historical records’ and the words ‘observed’ as well. As Tom Fuller points out there is much better observation these days that goes together with better (official) recording of events.
I suggest you read Hubert Lambs book ‘Historic Storms of the North Sea, British Isles and Northwest Europe’ which although not directly related to the area you describe nevertheless gives us a good insight into past storm activity.
ryan: i’m well aware of the issues with the best-track, in the Atlantic, Pacific, and globally, i recall publishing something on it a few years ago… i wrote a whole dissertation on intense extratropical storms, and am aware of the Lambs book. Sometimes u need to just put the skepticism aside and simply look in wonder at what nature does all on its own…

Can you help me out here please? The Saffir Simpson scale for categorising Hurricanes was only introduced in 1970.
How do we therefore retrospectively categorise Hurricanes that existed prior to this new standard?
ryan: simply according to the maximum recorded wind speed in the best-track database.

I have no idea if this will come across or not and even if it does, you may not want to show it. If not just delete. This is a screen capture of my OSXplanet screen. I am not sure where the program gets its data from but storms are supposed to be updated every three hours.[no link or attachment . . . b.mod]


“ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…”
Just checking I have this right. Are we expecting the jet stream to be sucked southerly by these storms, a bit like the “ox bow” loop that came southerly last winter?
And is this a good model to follow that progression?
If not, could someone recommend a similar animation type display. Thanks.

tonyb says:
I suggest you read Hubert Lambs book ‘Historic Storms of the North Sea, British Isles and Northwest Europe’ …

Oh yes, such good advice! Enjoy the wind in your hair right now, but whenever you feel sucked into the present, just open up a Hubert Lamb. It’s a pity the picture quality was so poor but the text rewards. That man is a giant of climate history obscured (as a sceptic) by the present scare of our supposed un-precendent-ed climate. He’s got the the grand scope, the big-picture-in-the-small in that marvellously British sober and nuanced story telling.
Meanwhile in our small picture we have passed a SOI mile record of 2.5 years, and so with IOD still in neg, the deluge of the great southern land looks set to continue into our temperate spring and the southern flip of the tropical monsoon….

Nice picture:
The graphic file
seen on the HTML page is NOT recognized by Firefox! (The name changes every hour.)
Try to open the EUMETSAT files in Firefox and Opera browsers. Opera is able to open it without problem, Firefox see it as binary file and wants to save it. Probably the moronic Firefox comes from “Windows School of Doing Things in 1995”, where type of file is read from file extension instead of first few bytes of a file. Pathetic.

Follow up to EUMETSAT picture.
There is a note above the picture window: Zoom: SHIFT key pressed and Drag on the image. Make use of it as the picture is much bigger than the image window on EUMETSAT html page.

Steven mosher

Ryan are you gunna stay up all night and watch storm tracks
ryan: waiting for 5 AM AST advisories to update the post. i have work at Navy Lab in morn.

kadaka (KD Knoebel)


1 Knot = 1 Nautical Mile per hour
1 Nautical mile = 6076.12 ft. = 1852 m **
1 Statute mile = 1760 yards = 5280 feet
** Definition: [n] a unit of length used in navigation; equivalent to the distance spanned by one minute of arc in latitude; 1,852 meters
1) Also called: international nautical mile, air mile a unit of length, used esp. in navigation, equivalent to the average length of a minute of latitude, and corresponding to a latitude of 45°, i.e. 1852 m (6076.12 ft.)
2) a former British unit of length equal to 1853.18 m (6080 ft.), which was replaced by the international nautical mile in 1970

1 knot = 1.152 miles per hour = 1.85 kilometer per hour
What is this stuff I’ve heard about the US going metric someday (there’s supposed to be a federal law about it) and metric is the system used in the sciences (like meteorology)? And now we’re using obscure seafarer units? How many fathoms deep do storms like this disturb the ocean?


Measurements of AMO ought show the warm phase cools. Will the warm phase recover, or is this the beginning of the end for the AMO’s warm phase?

John A

All of that energy wasted on fish. Its a crime.


Jay Currie said: “And each one of these storms sucks heat out of the ocean and sends it on its way.”
Like a giant vortex tube.

mike sphar

Two Majors and a minor on the Wide screen . Its an amazing site. especially from the Eastern tip of Puerto Rico which is still quite close to the main feature. Next week back to the hurricane safe harbor of Northern Nevada.

George Turner

We are all doomed, doomed I say!
Repent, and watch The Weather Channel
<— read a book on the history on the history of The Weather Channel because watching The Weather Channel was just to exciting and stressful.

George Turner

[George, check out the guide to WUWT linked on the right side of this page near the top, check out formatting tips ~ ctm]


The USA MSM who are panic junkies at the best of times, will go completely hysterical over this. Expect hours on end of a ruggedly heroic Anderson Cooper with hair dramatically flapping in the wind. I wonder if they will evacuate the entire eastern US seaboard?

kadaka (KD Knoebel)

For Severe Weather Like This, You Should Have
Keep Track Of The Storms
Receive Personalized Alerts
Know When Severe Weather Is Approaching
Think Of The Children!

(This has been an unsolicited uncompensated recommendation by someone who just happens to think it’s a good thing to have.)

OMG! It’s worse than we thought!!

Jimmy Haigh

Wot?! No warmists telling us all that they told us so yet?


Wot?! No warmists telling us all that they told us so yet?

Patience, Grasshopper.


Oh no – it’s exactly as we thought. CAGW is spawning unprecedented storms which will only provide a temporary reprieve from the catastrophic warming to follow. Donations gratefully accepted.


Jimmy Haigh says:
September 15, 2010 at 2:45 am
Wot?! No warmists telling us all that they told us so yet?

The stampede will come soon enough, just as soon as they figure out where both will hit back to back.
Have any 2 hurricanes ever hit the same place in rapid succession?

Jose Suro

Impressive! Patterns like this one are unsustainable though. It should change in a week or so, especially if moisture in the Indian Ocean keeps retreating east away from the East coast of Africa, as it is doing now. Tropical activity should shift to the Caribbean and (hopefully not) the southern Gulf of Mexico.

Great post, Ryan. The more you know, the better off you are. It is this kind of data that will help to demonstrate the reality of climate change and its sources of variation.
Julia will run into some of Igor’s outflow so it may calm down shortly. Bermuda, OTOH, better batten down the hatches. Karl (Junior? lol) may yet be reborn in the GoM seeing how Hermine got charged up in that bathwater….
What awaits us, this season, is a really active period to the end of October. We appreciate your work and getting it out there where we can access it. Kudos.

Tom in Florida

Are the wind speeds for Julia estimates from satellite photos and estimated pressure numbers or did a hurricane hunter aircraft actually fly in and measure them?

Scott B

@Tom in Florida:
The wind speeds and pressures for Julia and Igor are just from satellite estimates. The hurricane hunters typically don’t fly further out than 60W to sample a storm. I think they do sometimes if the storm is threatening the Leeward Islands, but both of these storms should move well north of them.


While having two cat 4s simultaneously is almost without precedent in our records, let’s remind ourselves that since the satellite era, we now have the ability to identify hurricanes in the open ocean far from land, and to accurately classify their wind speed.
Chris Landsea was lead author of an article about a year ago showing that there has been no upward trend in the number of hurricanes per decade hitting land, and that the decades which featured the largest numbers of major hurricanes were in the 1800s. I think WUWT even had a blog on the article. Those results contrasts with what you get with the satellite record, where there are upward trends in the last few decades. That upward trend is an artifact of the satellite record, where we now identify hurricanes which live and die hundreds of miles from land.
So here is a question: if this were 1920 or 1950, would we know that either of these hurricanes was a class 4? If I had to guess, it is possible that in 1950 there would have been enough ships to have intersected Igor to say “yes”, but that isn’t a given. However, if Julia doesn’t stay a class 4 for very long, given where it currently is, far from shipping lanes and only recently a major hurricane, I would guess that we would never know that it was a class 4. If it degrades to a cat 1 in a few days and turns north well east of Bermuda, how possible is it that we might not have known of its existence?
So perhaps it would be better to say that it is unprecedented — in the 30 or so years of the satellite record — to have two cat 4s in the N Atlantic.
That said, it does appear to be consistent (there’s that dreaded word again) with the notion that in a warmer world there will be more powerful hurricanes.
The counter argument, as Ryan Maue has said before, is that the total ACE in the N Hemisphere, and in the world, had NOT been trending upward, with the largest ACE amounts since 1979 occurring in 1993 and 1998. That isn’t so consistent with the idea of ever more powerful storms.
Bottom line: two cat 4s at the same time is pretty impressive, but I don’t want to take any climate change implications just yet.

I said
“Can you help me out here please? The Saffir Simpson scale for categorising Hurricanes was only introduced in 1970.
How do we therefore retrospectively categorise Hurricanes that existed prior to this new standard?”
ryan replied
“: simply according to the maximum recorded wind speed in the best-track database.”
Thanks for that Ryan. Would the maximum recorded wind speed recorded in say 1926 be using the same sensitivity of equipment and have been located in exactly the right place to have been able to accurately record a maxium wind speed?
Sorry, I am not trying to be difficult, just trying to compare like with like.

Ryan-my post at 5.43
I should have said that I am aware of the Hurricane reanalyis programme and that many aspects of past climate are subject to revisionism
As with thermometers, or say rain gauges, unless you have the equipment in exactly the right place at the right time you might not be capturing the extremes accurately.
When the nature of that equipment changes from the simple and local to the complex and universal the differences can become accentuated and can capture extremes outwith of the capabilties of the ‘old’ system to find.

Ulric Lyons

I would suggest keeping an eye on the solar wind velocity for changes in storm intensity and track.


ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…
The pulse of big blobs of tropical moisture & rain northward is often counteracted by a similarly large pulse of cold air southward to follow behind it. The passage of Hugo in VA years ago caused frosts in late Sept, well before the average first-frost.

Yikes – I completely missed yesterday’s publication of Colorado State University Forecast of Atlantic Hurricane Activity from September 15 – September 28, 2010 and don’t have time to write my usual minimal guest post for it. Let’s just let it ride here. I’ll pay attention for the next one. Hmm, hey Anthony, this is about my usual guest post size – if you’d like I can fish out the “usual” graphic of storm activity tonight and we can give this its own post. Probably little point in it though.
Lessee. Various quotes [comments in square brackets]:
We expect that the next two weeks will be characterized by above-average amounts of activity (greater than 130 percent of climatology.) [The forecast quantity is ACE, Igor and Julia by themselves may meet the forecast.]
The above-average forecast is due to a combination of factors. The primary factor is that we expect a very large amount of ACE to be generated by Igor. Current forecasts of Igor’s intensity from the National Hurricane Center indicate that this hurricane alone could generate enough ACE to approach the above-average definition. Julia is also expected to generate several ACE units as it tracks northwest across the Atlantic. Newly formed Karl could also help contribute modest amounts of ACE for the next several days. In addition, several of the global models are developing the next tropical wave moving off of the coast of Africa. The MJO is predicted to remain weak over the next two weeks, so we continue to primarily rely on currently-existing tropical cyclones and global model forecasts for this outlook. [Hey Richard Holle – have you ever looked at the correlation between the MJO and lunar tides? I seem to recall the MJO is about that timescale.]
[Page 3 – nice graphics of the storm tracks for the forecast period and the updated activity graph I used on the previous forecast posts.]
[From the five factors they look at:]
3) Global Model Analysis
The global models are fairly enthusiastic about developing the next wave off of the coast of Africa into a tropical cyclone. The GFS also hints at additional development possible in the 7-10 day timeframe. [Yep, those models sure can wax enthusiastic.]
Verification of September 1 September 14, 2010 Forecast
The two-week forecast of tropical cyclone activity from September 1 – September 14 looked to verify quite well until Hurricane Igor’s rapid intensification over the past couple of days. Activity at average levels (70-130%) was predicted, while observed activity was just outside the average category (approximately 140%) during the two-week period, due in large part to Igor’s copious ACE generation. As was the case during the last part of the August, most of the activity that occurred was in the tropical Atlantic’s Main Development Region. It appears that, in general, low-level winds were very favorable for storm formation during the two-week period. For example, low-level horizontal divergence was below-average, indicating increased low-level convergence which helps increase the likelihood of storm formation and intensification.
Several storms contributed to ACE during the two-week period, with most of the ACE being generated by Hurricane Earl during the early part of the period and Hurricane Igor during the latter part of the period. The Madden-Julian Oscillation was of a fairly weak magnitude throughout the period and likely did not play much of a role in modulating TC activity (Figure B).

Tom in Florida

Scott B says:{September 15, 2010 at 5:09 am}
“@Tom in Florida:
The wind speeds and pressures for Julia and Igor are just from satellite estimates. ”
Exactly, so when it is reported that this is the only the second time we’ve had two Cat 4 storms together, one must take it with a grain of salt. Prior to satellite coverage how would one know if this hadn’t happened more than once before, especially so far out in the Atlantic.

Leon Brozyna

With all the excitement focused on the rarity of two simultaneous major hurricanes (even if only fish storms), the footnotes are where all the action is:
— Igor looks (so far) to be on track to slam Bermuda. Well, there go all those vacation/honeymoon plans. Let’s hope they only experience property damage.
— TS (and maybe Hurricane when it hits) Karl will yet again do a number on the east coast of Mexico, already having experienced Alex and Hermine. Might not be majors, but that’s small comfort to the poor farmer in the hills watching his small abode float away in the floods these storms bring to Mexico’s inland regions.

Marcus K

Thanks for the update. I’m also enjoying the pacific coastal fog while marveling at these Atlantic storms.
Perhaps the lack of big storms in August increased the odds of multiple majors since the ATL basin has remained relatively free of upwelling. 2005 conditions were also ideal for development but the constant parade of storms created too much competition limiting the chances for concurrent majors. It reminds me of my storm chasing days when the best supercells seemed to occur close to sunset on the days when there was no activity anywhere during the afternoon.
With tropical Atlantic SST anomalies near record highs and a developing La Nina, have you looked into the possibility that we could be setting up for a significant farm belt drought next year? I know there have been studies suggesting the dust bowl years were characterized by a large tropical SST differential between the Pacific and Atlantic basins (cool Pacific, warm Atlantic). Does the current situation and forecasts bear enough similarity to that of the 1930’s that we should be concerned?
ryan: The SSTs are above average, but storms do not form due to the SST anomaly. It is likely that the atmospheric conditions of lower vertical shear allowed the African easterly waves to organize quicker than normal. When they come off of Africa with low-level circulations already (like midwestern US mesoscale convective systems) in La Nina years, they develop quickly. But the Cape Verde season is relatively short, and only a few more weeks of activity out there is normal.
Similarity in climate — as with analogs in weather — is a risky business. You can never have the exact same climate conditions in terms of SST patterns, and then there is no guarantee that the nonlinear feedbacks will even operate in the same sign let alone the same way. Think of the radically different forecast tracks of a hurricane you get with different weather forecast models…


2 thoughts,
yesterday they predicted that Julia would lose strength…hmmmm
and if this curves the jet stream down to Eastern Canada/US, perhaps this will allow some of that unprecedented warmest 2010 temperatures into Western Canada Prairies…

Douglas Dc

To giant-heat sucking vacuums in the North Atlantic at the same time. As others have said this has probably happened before-but better detection is the operative word here…

Dave F

Wow, we should be glad for satellites. I wouldn’t want to sail through two of those back-to-back. Is it possible for hurricanes to join together?
ryan: one can absorb another…but if they don’t “combine” they pinwheel around a center-of-mass just like our heavenly bodies in the solar system

Pamela Gray

Wouldn’t call this unprecedented unless qualified with “in the historical record”. It’s not like the pilgrims could see what was going on in the Atlantic by standing on the shore with a good eye-scope. Given the long history of the present location of the Atlantic, it stands to reason this has happened before.

Pamela Gray

I know the article includes that phrase, but commenter load tends to steer away from the original text and reverts to just the word “unprecedented” without the modifier.
ryan: if you follow my musings elsewhere at climateaudit and on my personal page: tongue in cheek.


September 15, 2010 at 3:38 am
“Have any 2 hurricanes ever hit the same place in rapid succession?”
I seem to remember Florida getting slammed pretty hard by a couple right in a row during the mid 90s. I think one even went over the panhandle and hooked back for a second chance at destruction. I’m gonna havta google it when I get home tonight.
BTW, Me and a few co-workers were talking about the possibility of a late season, with all of the major energy coming after the halfway point, but having three systems with two huge ones, and one of those nearing gigantic, just, well, blows me away.
ryan: the past 60-years when taking account El Nino and La Nina: no discernible correlation between activity during the first half and the second half of the season. it’s a crapshoot…

Lance says:
September 15, 2010 at 7:10 am
> yesterday they predicted that Julia would lose strength…hmmmm
I’m not sure how it developed so much. From the satellite imagery Julia looks awfully ratty for a Cat-4 storm. Then again, most Cat-4s had several days to get their act together and develop a good symmetric “firing on all cylinders” pattern.
BTW, in 2005 or so at one point there were 4 or 5 named storms, I think a record for the satellite era. Must’ve been a bunch of exhausted mets at the NHC that day.
ryan: it’s fortunate that Julia is a fish storm — and the track of Igor was pretty well cemented days ago. It is a threat to Bermuda for sure. Karl is relatively weak compared to those monsters. With no imminent US landfall threats, the public warning machinery at NHC is on respite.

rbateman says:
September 15, 2010 at 3:38 am
> Have any 2 hurricanes ever hit the same place in rapid succession?
One year recently had two or three hit the Cape Hatteras area, I think one pair was separated by a week or so. No time to check today. Wikipedia’s annual summaries might be the easiest place to look.