July Atlantic hurricane outlook

By: Dr. Jeff Masters , 12:55 PM GMT on July 13, 2012

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It's mid-July, and we have yet to see a named storm form in the Atlantic this month. The computer models are not predicting any development through at least July 20, and if we make it all the way to the end of the month without a named storm forming, it will be the first July since 2009 without a named storm. Since the current active hurricane period began in 1995, 13 of 17 years (76%) have had a named storm form during July. The busiest July occurred in 2005, when five named storms and two major hurricanes formed. These included Hurricane Dennis and Hurricane Emily--the strongest hurricanes ever observed so early in the season. Only eight major hurricanes have formed in July since record keeping began in 1851. As seen in Figure 1, most of the last half of July activity occurs in the Gulf of Mexico and waters off the Southeast U.S. coast. These type of storms form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance (as happened for Alberto, Beryl, Chris, and Debby in 2012.) There will be at least two cold fronts moving off the U.S. Mid-Atlantic coast over the next two weeks. The first of these fronts will push offshore around July 20, and we will need to watch the waters offshore of North Carolina for development then. Formation potential will be aided by ocean temperatures that are about 0.7°C (1°F) above average along the U.S. East Coast.


Figure 1. Tracks of all tropical storms and hurricanes 1851 - 2006 that formed July 16-31. The U.S. coast from North to Texas are the preferred strike locations. Only a few storms have formed in the tropical Atlantic and Caribbean in July. Wind shear is typically too high and SSTs too cool in July to allow African waves in the Caribbean and tropical Atlantic to develop into tropical storms. However, a few long-track "Cape Verdes" hurricanes have occurred in July, spawned by tropical waves that came off the coast of Africa. African tropical waves serve as the instigators of about 85% of all major hurricanes.


Figure 2. The seasonal distribution of Atlantic hurricane activity shows that July typically has low activity. Image credit: NHC.

Sea Surface Temperatures: slightly above average
The departure of Sea Surface Temperatures (SST) from average over the tropical Atlantic between Africa and Central America was about 0.3°C above average during June (Figure 3.) This figure has not changed much over the first two weeks of July. These temperatures are not warm enough to appreciably affect the odds of a July named storm or hurricane. The strength of the Azores-Bermuda high has been near average over the past two weeks, driving near-average trade winds. The latest 2-week run of the GFS model predicts continued average-strength trade winds through late-July, so SSTs should remain about 0.3°C above average during this period, due to average amounts of cold water mixing up from below due to the wind action on the water.


Figure 3. Sea Surface Temperature (SST) departure from average for July 12, 2012. SSTs were 0.3°C above average over the tropical Atlantic's Main Development region for hurricanes, from Africa to Central America between 10° and 20° North Latitude. Note the large region of above average SSTs along the Equatorial Pacific off the coast of South America, the hallmark of a developing El Niño episode. Image credit: NOAA/NESDIS

El Niño on the way?
For two consecutive weeks, ocean temperatures 0.5 - 0.6°C above average have been present in the tropical Eastern Pacific, which is right at the threshold for a weak El Niño episode. NOAA's Climate Prediction Center has issued an El Niño Watch, and gives a 61% chance that El Niño conditions will be present during the August - September - October peak of the Atlantic hurricane season. The likely development of a full-fledged El Niño episode means that Atlantic hurricane activity will probably be suppressed in 2012, due to the strong upper-level winds and high wind shear these events typically bring to the tropical Atlantic.


Figure 4. Sea Surface Temperature (SST) departure from average for the the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region"). El Niño conditions exist when the SST in this region rises 0.5°C above average. As of July 9, 2012, SSTs in the Niño 3.4 region had risen to 0.5°C above average. To be considered an "El Niño episode", El Niño conditions must occur for five consecutive months, using 3-month averages. Image credit: NOAA Climate Prediction Center.

Wind shear: above average
Wind shear is usually defined as the difference in wind between 200 mb (roughly 40,000 foot altitude) and 850 mb (roughly 5,000 foot altitude). In most circumstances, wind shear above 20 knots will act to inhibit tropical storm formation. Wind shear below 12 knots is very conducive for tropical storm formation. High wind shear acts to tear a storm apart. The jet stream has two bands of strong high-altitude winds that are currently bringing high wind shear to the Atlantic. The southern branch (subtropical jet stream) is bringing high wind shear to the Caribbean, and the northern branch (polar jet stream) is bringing high wind shear to the waters offshore of New England. This configuration often leaves a "hole" of low shear between the two branches, off the Southeast U.S. coast and over the Gulf of Mexico. The jet stream is forecast to maintain this two-branch pattern over the coming two weeks. Wind shear has been about 10 - 20% higher than average over the first two weeks of July, and is predicted to be mostly above average for the coming two weeks. This will cut down on the odds of a July storm.


Figure 5. Vertical instability over the Caribbean Sea in 2012 (blue line) compared to average (black line.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Instability has been lower than average, due to an unusual amount of dry air in the atmosphere, reducing the potential for tropical storm formation. Image credit: NOAA/NESDIS/CIRA.

Dry air: above average
As seen in Figure 5, there has been an unusual amount of dry, stable air in the Caribbean this year creating low levels of vertical instability. This has occurred due to a combination of dry air from Africa, and upper-atmosphere dynamics creating large areas of sinking air that dry as they warm and approach the surface. The Gulf of Mexico and tropical Atlantic between the coast of Africa and the Lesser Antilles have also seen low vertical instability this summer. June and July are the peak months for dry air and dust coming off the coast of Africa, and the Saharan dust storms have been quite active over the past two weeks. Expect dry air to be a major deterrent to any storms that try to form in the tropical Atlantic during July.

Steering currents: average
The predicted steering current pattern for the next two weeks is a typical one for July. We have an active jet stream bringing many troughs of low pressure off the East Coast of the U.S. These troughs are frequent enough and strong enough to recurve any tropical storms or hurricanes that might penetrate north of the Caribbean Sea. Steering current patterns are predictable only about 3 - 5 days in the future, although we can make very general forecasts about the pattern as much as two weeks in advance. There is no telling what might happen during the peak months of August, September, and October--we might be in for a repeat of the favorable 2010 and 2011 steering current pattern, which recurved most storms out to sea--or the unfavorable 2008 pattern, which steered Ike and Gustav into the Gulf of Mexico.

Summary: a below average chance of a July tropical storm
Given that none of the computer models are forecasting tropical storm formation in the coming seven days, SSTs are only slightly above average, and wind shear and vertical stability are above average, I'll go with a 30% chance of a named storm forming in the Atlantic during the remainder of July.


Figure 6. Hurricane Emilia over the Eastern Pacific at 20:35 UTC July 10, 2012. At the time, Emilia was a Category 3 hurricane with 125 mph winds. Emilia peaked earlier in the day as a Category 4 storm with 140 mph winds--the strongest hurricane in the East Pacific so far in 2012. Image credit: NASA.

An active Eastern Pacific hurricane season
It's been a very active start to the Eastern Pacific hurricane season, where we've already had six named storms, four hurricanes, and three intense hurricanes. A typical season has 4 named storms, 2 hurricanes, and 0 intense hurricanes by July 14. The formation of Tropical Storm Fabio on July 12 marks the 4th earliest formation of the Eastern Pacific's season's sixth storm. The record is held by the year 1985, when the season's sixth storm formed on July 2. Record keeping began in 1949.

Have a great weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

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Quoting washingtonian115:
Nope Gro.What do you think of possible development off of Africa next week?.


Gee, I don't know. I guess we'll have to wait for the experts.
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Quoting washingtonian115:
It's running right into south america and could eventually aid in development in the east pacific.

Well, we look forward to more rain then.
I better enjoy the next 2 days of relative dry.
Today was nice and hot & Breezy.
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Quoting Grothar:




You people don't miss anything, do you?
Nope Gro.What do you think of possible development off of Africa next week?.
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Quoting Articuno:

If I told you I like mountain dew, it would be no different.?


That might be different.
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Fabio:

Member Since: July 21, 2011 Posts: 82 Comments: 7056
Quoting washingtonian115:
It's running right into south america and could eventually aid in development in the east pacific.


Quoting Articuno:

...on a crash course into south america


You people don't miss anything, do you?
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Quoting KoritheMan:


Because Cody likes it.

OOOOOH SNAP

If I told you I like mountain dew, it would be no different.?
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Quoting Grothar:
Small wave way South in Atlantic.


...on a crash course into south america
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Quoting Grothar:
Small wave way South in Atlantic.

It's running right into south america and could eventually aid in development in the east pacific.
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Quoting barbamz:


You surely know, "old swede" it's a figure of speech in German.
http://de.wikipedia.org/wiki/Alter_Schwede_(Redew endung)

And rain won't stop tonight in Germany but already for weeks it didn't and it won't in the UK (poor Olympics):

Would someone please tell us why it won’t stop raining?As the Met Office forecasts yet more downpours, what’s behind the bad weather, asks Michael Hanlon.

In answer to your queriy!
"Would someone please tell us why it won’t stop raining?As the Met Office forecasts yet more downpours, what’s behind the bad weather, asks Michael Hanlon."
For every degree that the average atmospheric temps rise by 1 degree then 4% more water can be carried by the atmosphere.
Its going to rain on and off for a long time! Sorry if it upsets anybody's plans but that's just global warming for you!
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Member Since: July 21, 2011 Posts: 82 Comments: 7056
650. yoboi
Quoting Articuno:

Um...Don't you mean 4,500 to 5,000?
Because Mt. Everest is 29,029 ft



could be tops of storms idk
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Quoting Articuno:

Y U NO LIKE MOUNTAIN DEW!!


Because Cody likes it.

OOOOOH SNAP
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Small wave way South in Atlantic.

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Some strong vort in the north eastern part of the Gulf.Low pressure area trying to get it's act together all though convection has been limited all day long.
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Quoting KoritheMan:


Better than ******* Mountain Dew.

Y U NO LIKE MOUNTAIN DEW!!
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Quoting HurricaneHunterJoe:
Flash Flood Warnings,Severe Thunderstorm Warnings for the Mountains and Deserts of Southern California up to 45,000-50,000 feet.


Um...Don't you mean 4,500 to 5,000?
Because Mt. Everest is 29,029 ft
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644. yoboi
Quoting aislinnpaps:


Good beer and good wine


and good brochen and...



is brochen like boudain???
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Quoting TropicalAnalystwx13:

I call BS.


I call BS on your BS.
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641. yoboi
Quoting barbamz:


Rain and beer will go together very well: Somewhere in Germany last weekend

Giggle translation:
09/07/2012 Viersen (RP). The Dülkener beer market at the weekend was a wet fun with small obstacles.

About 250 types of beer were on offer this time of the "Fritz-Walter-beer" on Pils, Alt, and wheat from Poland, Czech and German monasteries, but also many other drinks such as Ritterfurz and Jungfernglut or Sarazenenblut: The Middle Ages did greet. Even the butler was busy and got himself approached the young men standing around. Not to drink with them, you should hit the "Luke" and hit the ball with the little bell hanging high above. The bright blade rang again and again over the place and painted the jaunty rhythms, chatted with them "coffee substitute" the guests. But as the saying of Schiller: With the powers of destiny is not an eternal covenant to weave!

The radiant sun just barely hid, dark clouds moved over Dülken and a heavy downpour caused the guests to escape to the big screens of the breweries. The rain did not last long, so a happy toast to midnight nothing stood in the way. A dry and hot Saturday was the heart of Beer hosts a beat, Dülken was again a huge beer garden up - yes, on Sunday, the weather, unfortunately, law retained: it was changeable, ever again rain showers, uncomfortable flat and no pleasure.



nice, rain and beer can't go wrong with that...
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Quoting Grothar:


Norwegian-German-Italian

Good Grief!
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Quoting PlazaRed:

At Last! At Last!
Somebody, who doth spake sense?
Thank you for that one.
I've been looking at how the pattern will set up next week for three weeks now.I wasn't surprised when the models started to sniff out a possible strong tropical wave/storm.
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Quoting PlazaRed:

Are you Norwegian?


Norwegian-German-Italian
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Quoting yoboi:



do they have good beer there?


Good beer and good wine


and good brochen and...
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Quoting KoritheMan:


Better than ******* Mountain Dew.

I call BS.
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Quoting yoboi:



do they have good beer there?


Rain and beer will go together very well: Somewhere in Germany last weekend

Giggle translation:
09/07/2012 Viersen (RP). The Duelken beer market at the weekend was a wet fun with small obstacles.

About 250 types of beer were on offer this time of the "Fritz-Walter-beer" on Pils, Alt, and wheat from Poland, Czech and German monasteries, but also many other drinks such as Ritterfurz and Jungfernglut or Sarazenenblut: The Middle Ages did greet. Even the butler was busy and got himself approached the young men standing around. Not to drink with them, you should hit the "Luke" and hit the ball with the little bell hanging high above. The bright blade rang again and again over the place and painted the jaunty rhythms, chatted with them "Muckefuck" the guests. But as the saying of Schiller: With the powers of destiny is not an eternal covenant to weave!

The radiant sun just barely hid, dark clouds moved over Duelken and a heavy downpour caused the guests to escape to the big screens of the breweries. The rain did not last long, so a happy toast to midnight nothing stood in the way. A dry and hot Saturday was the heart of Beer hosts a beat, Duelken was again a huge beer garden up - yes, on Sunday, the weather, unfortunately, law retained: it was changeable, ever again rain showers, uncomfortable flat and no pleasure.
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Quoting KoritheMan:


Better than ******* Mountain Dew.
Hey,hey now I like mountain Dew.Haven't had one in a month.let alone any soda.
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Quoting washingtonian115:
I think Ernesto is a good possibility next week.MJO should be over Africa and the high over the Atlantic should weaken some allowing dust not to be so strong coming off of Africa.

At Last! At Last!
Somebody, who doth spake sense?
Thank you for that one.
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632. yoboi
Quoting KoritheMan:


There may be some light easterly shear, but that isn't what's killing her. Dry air is; you can see the arc clouds emanating from the eastern quadrant if you examine water vapor imagery.


i see what ya talking about...
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Quoting TropicalAnalystwx13:

That's disgusting.


Better than ******* Mountain Dew.
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Quoting PensacolaDoug:






LOL!
rumor has it if one grabs a bottle from the in and out store it makes everything a little more enhanced
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I think Ernesto is a good possibility next week.MJO should be over Africa and the high over the Atlantic should weaken some allowing dust not to be so strong coming off of Africa.
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Quoting BobWallace:


That's an anomaly map, not a temp map.


I know. Warmer relative to normal. If you wish...





The Atlantic may have more areal warming, but the Pacific wins out on raw SSTs.
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Quoting washingtonian115:
Kori now I see it.Why has the MJO been stuck over there.i thought the MJO usually sticks around the warmest basin on the planet.

Not much of an oscillation if it doesn't oscillate.
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Quoting KoritheMan:
I've been dieting so much that I've forgotten the wonderful taste of Dr. Pepper. A treat every now and then is quite worth it.

That's disgusting.
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Quoting yoboi:




look at low and mid level winds from the nw of hw


There may be some light easterly shear, but that isn't what's killing her. Dry air is; you can see the arc clouds emanating from the eastern quadrant if you examine water vapor imagery.
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Quoting KoritheMan:


I do miss him.


I think someone said that he was going to be back at some point this season.Hopefully that is the case.
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623. yoboi
Quoting BobWallace:


That's an anomaly map, not a temp map.



your on ya A game today bob...
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Quoting KoritheMan:


The Pacific is warmer than the Atlantic:



That's an anomaly map, not a temp map.
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621. yoboi
Quoting aislinnpaps:


A couple of years ago I took my two younger kids to Germany to visit their brother (Reichenbach-steegan) and it was the same way, rain the entire time we were there. I did get some good pictures with great clouds in the background though.



do they have good beer there?
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Quoting LargoFl:
...............well thats it for me..good night everyone...TGIF


Woah..
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619. yoboi
Quoting KoritheMan:


You mean nonexistent?
Quoting KoritheMan:


You mean nonexistent?




look at low and mid level winds from the nw of hw
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I've been dieting so much that I've forgotten the wonderful taste of Dr. Pepper. A treat every now and then is quite worth it.
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Quoting barbamz:


You surely know, "old swede" it's a figure of speech in German.
http://de.wikipedia.org/wiki/Alter_Schwede_(Redew endung)

And rain won't stop tonight in Germany but already for weeks it didn't and it won't in the UK (poor Olympics):

Would someone please tell us why it won’t stop raining?As the Met Office forecasts yet more downpours, what’s behind the bad weather, asks Michael Hanlon.


A couple of years ago I took my two younger kids to Germany to visit their brother (Reichenbach-steegan) and it was the same way, rain the entire time we were there. I did get some good pictures with great clouds in the background though.
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Quoting barbamz:


You surely know, "old swede" it's a figure of speech in German.
http://de.wikipedia.org/wiki/Alter_Schwede_(Redew endung)

And rain won't stop tonight in Germany but already for weeks it didn't and it won't in the UK (poor Olympics):

Would someone please tell us why it won’t stop raining?As the Met Office forecasts yet more downpours, what’s behind the bad weather, asks Michael Hanlon.



Yes, I know. I was just having fun with you. My Plattdeutsch relatives always used that expression. (among others)
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Quoting washingtonian115:
I know ignorance is bliss and people forget that Climo is winning right now.It's tri-winning.Even in El nino seasons their is always an active point.And when one heads for you/effects you it's a "bad season".Let's see how you all change your tone in a month..

Tones are not for changing! Only the owner of the tone can change their perseption!
The season is nature, the obseverours of the season are human?
We may wilt and want for all that's not but reality is waiting to suprise us!
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Quoting washingtonian115:
Kori now I see it.Why has the MJO been stuck over there.i thought the MJO usually sticks around the warmest basin on the planet.


The Pacific is warmer than the Atlantic:

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Member Since: July 21, 2011 Posts: 82 Comments: 7056
Kori now I see it.Why has the MJO been stuck over there.i thought the MJO usually sticks around the warmest basin on the planet.
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Quoting washingtonian115:
I know ignorance is bliss and people forget that Climo is winning right now.It's tri-winning.Even in El nino seasons their is always an active point.And when one heads for you/effects you it's a "bad season".Let's see how you all change your tone in a month..


thats right
in a month
no time soon
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.