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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Enjoy the rest of the weekend everyone...good night!
Member Since: Posts: Comments:
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Quoting Ameister12:
Off to bed, but before I go, I'd like to share a very powerful hypothetical hurricane taking a very bad path.


AND THIS
Member Since: June 20, 2012 Posts: 0 Comments: 2159
Quoting biloxibob:
Could somebody explain to me how to post an image?( Im not computer literate)

Take the URL of the image (right-click --> Copy Image URL in Firefox and Google Chrome. Properties --> Address (URL) in Internet Explorer) and paste it into the box that comes up when you hit the "Image" button above the comment box.
Member Since: July 6, 2010 Posts: 113 Comments: 32072
Could somebody explain to me how to post an image?( Im not computer literate)
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Quoting TropicalAnalystwx13:

Models are un-enthused.
Quoting nigel20:

Agreed.
Yup, things are going to be boring for awhile.LinkLink
Member Since: March 16, 2012 Posts: 127 Comments: 7942
Observed at: Toronto Pearson Int'l Airport
Date: 12:00 AM EDT Saturday 14 July 2012
Condition: Partly Cloudy
Pressure: 30.13 inches
Tendency: rising
Visibility: 15 miles
Air Quality Health Index: 6

Temperature: 75.9°F
Dewpoint: 64.9°F
Humidity: 69 %
Wind: SSE 3 mph
Humidex: 87
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Off to bed, but before I go, I'd like to share a very powerful hypothetical hurricane taking a very bad path. D=
Member Since: August 9, 2009 Posts: 10 Comments: 4979
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Member Since: July 21, 2011 Posts: 83 Comments: 7167
Out for now. Blog update for anyone who missed it earlier.
Member Since: March 7, 2007 Posts: 576 Comments: 20612
Quoting tazmaniad:


please do not give directions for booozy drinks on this forum. many of the talkers are childs.


If anyone reading that is a child, chances are they won't be getting any ideas anyway. At least not ones they can bring to fruition.
Member Since: March 7, 2007 Posts: 576 Comments: 20612
Quoting wxchaser97:

Is this the next possible system in the epac, man do we need an Atlantic storm or things will go downhill.

Agreed.
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Quoting BobWallace:


Nasty?

Peach Mango Smoothie...

1 peach, sliced
1 mango, peeled and diced
1/2 cup vanilla soy milk
1/2 cup orange juice, or as needed
Directions

Place the peach, mango, soy milk, and orange juice into a blender. Cover, and puree until smooth. Pour into glasses to serve.

--















Strawberry Smoothie...

8 strawberries, hulled
1/2 cup skim milk
1/2 cup plain yogurt
3 tablespoons white sugar
2 teaspoons vanilla extract
6 cubes ice, crushed
Directions

In a blender combine strawberries, milk, yogurt, sugar and vanilla. Toss in the ice. Blend until smooth and creamy. Pour into glasses and serve.

Let your creativity run wild....
Quoting BobWallace:


Nasty?

Peach Mango Smoothie...

1 peach, sliced
1 mango, peeled and diced
1/2 cup vanilla soy milk
1/2 cup orange juice, or as needed
Directions

Place the peach, mango, soy milk, and orange juice into a blender. Cover, and puree until smooth. Pour into glasses to serve.

--

Strawberry Smoothie...

8 strawberries, hulled
1/2 cup skim milk
1/2 cup plain yogurt
3 tablespoons white sugar
2 teaspoons vanilla extract
6 cubes ice, crushed
Directions

In a blender combine strawberries, milk, yogurt, sugar and vanilla. Toss in the ice. Blend until smooth and creamy. Pour into glasses and serve.

Let your creativity run wild....


please do not give directions for booozy drinks on this forum. many of the talkers are childs.
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WOW Emilia weakened quick! When I went to work today she was a cat 2 hurricane :O Ok, was a long day...but surely not THAT long!
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Quoting wxchaser97:

Is this the next possible system in the epac, man do we need an Atlantic storm or things will go downhill.

Models are un-enthused.
Member Since: July 6, 2010 Posts: 113 Comments: 32072

Is this the next possible system in the epac, man do we need an Atlantic storm or things will go downhill.
Member Since: March 16, 2012 Posts: 127 Comments: 7942
Quoting VAbeachhurricanes:


Why is the eye over my house?


Cause it's travelling up the Chesapeake!
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CI# /Pressure/ Vmax
4.4 / 982.6mb/ 74.6kt


Final T# Adj T# Raw T#
4.4 4.4 4.2

Center Temp : -23.4C Cloud Region Temp : -53.0C

Scene Type : LARGE EYE

Positioning Method : SPIRAL ANALYSIS

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
Member Since: March 16, 2012 Posts: 127 Comments: 7942
Quoting WxGeekVA:
Imagine seeing this on December 21st, this year...



And yes, I spent 3 hours shopping Hurricane Igor into an as clear as possible satellite image of the United States on Microsoft paint (Because Photoshop is too mainstream and expensive)


Why is the eye over my house?
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Low pressure coming off Africa soon.
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
EP062012 - Hurricane FABIO

Enhanced Infrared (IR) Imagery (4 km Mercator)

Member Since: July 3, 2005 Posts: 424 Comments: 128344
Convection now around 2/3 to 3/4 wrapped around the eye.
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Quoting WxGeekVA:
Imagine seeing this on December 21st, this year...



And yes, I spent 3 hours shopping Hurricane Igor into an as clear as possible satellite image of the United States on Microsoft paint (Because Photoshop is too mainstream and expensive)
There would also be a hurricane impacting FL and the gulf coast, I'm not saying go use paint to make 2 more doom-canes. That is cool since it does look pretty real to me.
Member Since: March 16, 2012 Posts: 127 Comments: 7942
Quoting WxGeekVA:
Imagine seeing this on December 21st, this year...



And yes, I spent 3 hours shopping Hurricane Igor into an as clear as possible satellite image of the United States on Microsoft paint (Because Photoshop is too mainstream and expensive)

Oh my gooood!!!
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Quoting Ameister12:

Other than having to go to the dentist (I HATE the dentist!) my day was pretty good.

That's good to know.
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Member Since: March 16, 2012 Posts: 127 Comments: 7942
Imagine seeing this on December 21st, this year...



And yes, I spent 3 hours shopping Hurricane Igor into an as clear as possible satellite image of the United States on Microsoft paint (Because Photoshop is too mainstream and expensive)
Member Since: September 3, 2011 Posts: 13 Comments: 3471
Quoting nigel20:

Hey Kori!
Good evening Amiester...I'm good. How are you Doing?

Other than having to go to the dentist (I HATE the dentist!) my day was pretty good.
Member Since: August 9, 2009 Posts: 10 Comments: 4979
Quoting CaribBoy:
For those in PR complaining they've got to much rain recently: please note that WE ARE WELL BELOW AVERAGE IN THE LEEWARD ISLANDS :(

Hey CaribBoy...hopefully you'll get some relief soon!
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To be honest, I think 80 kt in kinda high for Fabio's current maximum sustained winds. He's still very ragged. I would have kept him at 70 kt wind speeds.
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Quoting redwagon:

Why else would you give Fabio a better foothold than he actually has, if you were the NHC?


The eye seen on satellite images.
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Quoting KoritheMan:


Good evening bro.

Hey Kori!
Quoting Ameister12:
Evening, Nigel. How ya doing?

Good evening Amiester...I'm good. How are you Doing?
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Quoting KoritheMan:


What? No he isn't. He is expected to dissipate well before making any sort of landfall. "Theoretically" is too strong a word.

Why else would you give Fabio a better foothold than he actually has, if you were the NHC?
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Evening, Nigel. How ya doing?
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Fabio will reach Cat 2 status and then begin to weaken soon thereafter.
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For those in PR complaining they've got to much rain recently: please note that WE ARE WELL BELOW AVERAGE IN THE LEEWARD ISLANDS :(
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Quoting nigel20:
Good evening everyone!

Daily SOI: 15.8
30 Day SOI: -7.2
90 Day SOI: -3.4


Good evening bro.
Member Since: March 7, 2007 Posts: 576 Comments: 20612
Good evening everyone!

Daily SOI: 15.8
30 Day SOI: -7.2
90 Day SOI: -3.4
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Quoting redwagon:

They have to be more liberal with Fabio because he's a theoretically land-falling cane and lots of folks need ample warning. The other two going W, no threat, they need to send the buzz out about Fabio.


What? No he isn't. He is expected to dissipate well before making any sort of landfall. "Theoretically" is too strong a word.
Member Since: March 7, 2007 Posts: 576 Comments: 20612
Quoting TropicalAnalystwx13:

Too high if you ask me. They factor in rapid intensification when the SHIPS is showing a meager 17% of it within 48 hours.

They didn't include RI in the forecast when the SHIPS showed 90% for Emilia.

They have to be more liberal with Fabio because he's a theoretically land-falling cane and lots of folks need ample warning. The other two going W, no threat, they need to send the buzz out about Fabio.
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting Ameister12:
NHC isn't being conservative with Fabio at all! A 95 kt peak is a lot higher than I would have expected.
Why is it when there is a strong impressive storm the NHC is conservative but with a medium strength average hurricane they are aggressive in the epac this year?
Member Since: March 16, 2012 Posts: 127 Comments: 7942

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

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