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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1611. Patrap
3 Man ISS/Soyuz Launch LIVE from Russia.
Member Since: July 3, 2005 Posts: 426 Comments: 128616
I don't know how to post images.You'll have to ask ncstorm.
Member Since: August 14, 2010 Posts: 10 Comments: 17069
A Higgs-Boson walks into a church...the priest says "We don't allow Higgs-Boson here"...the Higgs-Boson says " But....without me....How can you have mass?!?!"
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Quoting TropicalAnalystwx13:
They held Fabio at 90 knots. :(

Oh well. :(

Tropical Cyclone Report may later increase the intensity of Fabio.
Member Since: July 21, 2011 Posts: 83 Comments: 7167
1605. yoboi
Quoting midgulfmom:
if you do check out the seafood lot at bayou segnette on the expressway. (If you like seafood) They have swampboat tours there also. Kinda sad but when I moved here in '94 all my elderly neighbors still spoke cajun french but very few passed it on and there are only a few left who still do. They sound lkke Troy on swamp people. BTW during alligator season they used to have a market for that at the seafood lot but not sure they still do. Message me if you do and want some other sight seeing ideas.


will do i live in swla...
Member Since: August 25, 2010 Posts: 7 Comments: 2345
HURRICANE FABIO DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL EP062012
800 PM PDT SAT JUL 14 2012

FABIO HAS NOT CHANGED MUCH SINCE THE RELEASE OF THE SPECIAL ADVISORY
AROUND 0000 UTC. THE 20 N MI EYE REMAINS CIRCULAR AND DISTINCT IN
SATELLITE IMAGES...AND THE CONVECTIVE CLOUD PATTERN IS FAIRLY
SYMMETRIC. DVORAK CLASSIFICATIONS FROM TAFB AND SAB WERE BOTH 90
KT...THEREFORE THE INITIAL WIND SPEED IS HELD AT THAT VALUE.

IT SEEMS LIKELY THAT FABIO IS NEAR ITS PEAK INTENSITY...AS THE EYE
IS CLOSE TO THE 26C ISOTHERM. THE HURRICANE IS EXPECTED TO MOVE
OVER SUB-26C WATERS IN THE NEXT 12 TO 18 HOURS...AND THE SSTS ALONG
THE FORECAST TRACK STEADILY DECREASE BEYOND THAT TIME. THESE
UNFAVORABLE OCEANIC CONDITIONS...COMBINED WITH A DRIER AIR MASS
AHEAD OF FABIO SHOULD CAUSE SLOW BUT STEADY WEAKENING DURING THE
NEXT FEW DAYS. FABIO IS FORECAST TO BECOME A REMNANT LOW IN ABOUT 4
DAYS WHEN IT IS OVER WATERS OF ABOUT 20C AND ENCOUNTERS AND AN
INCREASE IN SOUTHERLY VERTICAL WIND SHEAR. THE OFFICIAL FORECAST IS
IDENTICAL TO THE PREVIOUS ADVISORY AND IN CLOSE AGREEMENT WITH
LGEM.

FABIO IS STILL MOVING WESTWARD AT ABOUT 8 KT. A WEST-NORTHWESTWARD
MOTION IS FORECAST DURING THE NEXT 24 HOURS AS MID-LEVEL RIDGING
HANGS ON TO THE NORTH OF THE SYSTEM. THEREAFTER...THE RIDGE IS
FORECAST TO BREAK DOWN AS A MID- TO UPPER-LEVEL LOW DIGS SOUTHWARD
OVER THE WESTERN UNITED STATES. THIS STEERING PATTERN SHOULD CAUSE
FABIO TO SLOW DOWN AND GRADUALLY TURN NORTHWARD. THE OFFICIAL TRACK
FORECAST LIES CLOSE TO THE TVCE CONSENSUS AND IS SIMILAR TO THE
PREVIOUS ADVISORY.

FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 16.4N 115.7W 90 KT 105 MPH
12H 15/1200Z 16.7N 117.1W 85 KT 100 MPH
24H 16/0000Z 17.2N 118.7W 75 KT 85 MPH
36H 16/1200Z 18.0N 120.0W 65 KT 75 MPH
48H 17/0000Z 19.0N 120.8W 55 KT 65 MPH
72H 18/0000Z 21.5N 121.3W 35 KT 40 MPH
96H 19/0000Z 23.5N 121.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 20/0000Z 25.0N 121.5W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
FORECASTER CANGIALOSI
Member Since: July 21, 2011 Posts: 83 Comments: 7167
BULLETIN
HURRICANE FABIO ADVISORY NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL EP062012
800 PM PDT SAT JUL 14 2012

...CATEGORY TWO FABIO CONTINUES WESTWARD...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...16.4N 115.7W
ABOUT 585 MI...945 KM SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...972 MB...28.70 INCHES
Member Since: July 21, 2011 Posts: 83 Comments: 7167
They held Fabio at 90 knots. :(
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Quoting yoboi:



1957 was a bad yr for swla


Yes it was. :(
Member Since: August 24, 2010 Posts: 0 Comments: 245
Quoting yoboi:


i will have to make a road trip and check it out..
if you do check out the seafood lot at bayou segnette on the expressway. (If you like seafood) They have swampboat tours there also. Kinda sad but when I moved here in '94 all my elderly neighbors still spoke cajun french but very few passed it on and there are only a few left who still do. They sound lkke Troy on swamp people. BTW during alligator season they used to have a market for that at the seafood lot but not sure they still do. Message me if you do and want some other sight seeing ideas.
Member Since: Posts: Comments:
1599. yoboi
Quoting AtHomeInTX:
A very unofficial glimpse at storms that have hit here, meaning TX/LA. But by no means all that affected us. Including the last 2 in 2008 Ed and Ike.

14 ts, 1 td, 5 H1, 4 H2, 3 H3, 1 H4

A few other notables:

The storm no one remembers from 1957 (for obvious reasons)



Some majors






1957 was a bad yr for swla
Member Since: August 25, 2010 Posts: 7 Comments: 2345
Depends on if the el nino by that point get's to strong or not.El nino usually causes shear in the caribbean.And that area is a hot spot for for storms to form in October/November.
Member Since: August 14, 2010 Posts: 10 Comments: 17069
Quoting yoboi:


what's your thoughts with fabio??



it sould start too weak in tonight
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Quoting TropicalAnalystwx13:

I'm expecting the two months to be quite busy, yes. We should expect at least 9 more named storms this season.
Agreed.Maybe a storm or two for October..
Member Since: August 14, 2010 Posts: 10 Comments: 17069
1593. yoboi
Quoting midgulfmom:
m-f 9 to 4 I think....3rd block of Sala Ave off of River Road. It's a time warp...so cool. They bought the old hardware general store from the owner who retired in the mid 90's. They kept most of it the same. Looks exactly like Ike's General Store on the Waltons! I swear! They still had War Bond posters in there when I moved here....Movie companies have checked it out for possible scene settings. Just for thar reason it's worth a look see esp if you like history but call first to check hours. More info on City of Westwego page.


i will have to make a road trip and check it out..
Member Since: August 25, 2010 Posts: 7 Comments: 2345
1592. yoboi
Quoting Tazmanian:




nop


i got a TV


what's your thoughts with fabio??
Member Since: August 25, 2010 Posts: 7 Comments: 2345
Quoting Dull2012:


Nine more?

Three in August, four in September, and two between October and November.
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Assuming for a moment that we do not get any storms in July (typical climatology with the 1.72 average for June-July), we know that late-May/June with 4 storms was a historic period. Right now, and particularly with the activity in the E-Pac, we are back to normal July climatology in the Atlantic. With the exception of any storms that may form from frontal remnants near the US Coasts or Western Caribbean over the next several weeks, the action will shift to the African waves; what we do not know is whether the CV formation period will start in early-mid or late August.

Either way, all of the ingredients have to pretty much gel at the same time to favor formation. While the recent waves passing across Florida and into the Gulf were in the right place (low sheer and warm waters), the large scale synoptic pattern in place over the Gulf region, and particularly the large ULL in the Central Gulf north of the Yucatan Peninsula, prevented any significant development; they came through at the wrong time.
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Quoting yoboi:



did ya get ya new comp??




nop

see post 1585
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Quoting yoboi:



how often are they open??
m-f 9 to 4 I think....3rd block of Sala Ave off of River Road. It's a time warp...so cool. They bought the old hardware general store from the owner who retired in the mid 90's. They kept most of it the same. Looks exactly like Ike's General Store on the Waltons! I swear! They still had War Bond posters in there when I moved here....Movie companies have checked it out for possible scene settings. Just for thar reason it's worth a look see esp if you like history but call first to check hours. More info on City of Westwego page.
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but i did get a nic new 39" 1080p TV on friday its a emerson



i i still have my 19" 720p TV its all so a emerson
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1584. yoboi
Quoting Tazmanian:




lol nop i be at home



did ya get ya new comp??
Member Since: August 25, 2010 Posts: 7 Comments: 2345
Quoting Dull2012:


Thanks. Are you still anticipating an explosive August and September? I read your blog a short while ago and you illustrated upon that possibility on it.

I'm expecting the two months to be quite busy, yes. We should expect at least 9 more named storms this season.
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Quoting yoboi:



taz are ya going to be on the pch with cantore looking for fabio???




lol nop i be at home
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1579. yoboi
Quoting Tazmanian:




is that all you no how too post?



taz are ya going to be on the pch with cantore looking for fabio???
Member Since: August 25, 2010 Posts: 7 Comments: 2345
When we get into months like August the Atlantic doesn't need to be dependent on the MJO.I think we'll eventually see something in the beginning of the month.The wave over Africa seems promising.
Member Since: August 14, 2010 Posts: 10 Comments: 17069
Quoting Dull2012:


Really, that long? But we would get development before-hand, no?

Maybe. We'll have to watch off the East Coast for frontal storms and in the East Atlantic by early August for tropical development.
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Quoting Civicane49:
Hurricane Fabio:





is that all you no how too post?
Member Since: Posts: Comments:
A very unofficial glimpse at storms that have hit here, meaning TX/LA. But by no means all that affected us. Including the last 2 in 2008 Ed and Ike.

14 ts, 1 td, 5 H1, 4 H2, 3 H3, 1 H4

A few other notables:

The storm no one remembers from 1957 (for obvious reasons)



Some majors



Member Since: August 24, 2010 Posts: 0 Comments: 245
ugh



well it was nic why it lasted



guss oh may be back guys
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Quoting Dull2012:


By when would you expect all of them to reenter the octane of our ocean, Cody?

It'll be a few weeks, probably not until mid-August.
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Hurricane Fabio:

Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting TomTaylor:
GFS no longer brings the MJO into our octant, all models in agreement on eastward propagation of the MJO across the Indian Ocean.

Multi Model MJO Phase Diagram



That means no new Kelvin Wave that transports the warm waters from west to east delaying El Nino prospects?
Member Since: April 29, 2009 Posts: 75 Comments: 14306
1569. yoboi
Quoting midgulfmom:
Good evening....read back and saw yall discussing the 1893 hurricane hitting Cheniere Caminada. I'm from N.O. but moved to Westwego just south of N.O. ...Westwego was created by the survivors of that storm who moved further north to settle. They have a museum here that chronicles the history of the storm and displays some interesting artifacts including a long hair braid of a woman whose life was saved due to that braid catching on a barbed wire fence. Thereby keeping her from being swept out into the gulf.



how often are they open??
Member Since: August 25, 2010 Posts: 7 Comments: 2345
Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting KoritheMan:


Take that back! Debby was at one point forecast to be in my backyard.
I think Debby was forecasted to be in everyone's basin at one point...
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Good evening....read back and saw yall discussing the 1893 hurricane hitting Cheniere Caminada. I'm from N.O. but moved to Westwego just south of N.O. ...Westwego was created by the survivors of that storm who moved further north to settle. They have a museum here that chronicles the history of the storm and displays some interesting artifacts including a long hair braid of a woman whose life was saved due to that braid catching on a barbed wire fence. Thereby keeping her from being swept out into the gulf.
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I've made a blog update on Fabio and Emilia.
Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting TomTaylor:
GFS no longer brings the MJO into our octant, all models in agreement on eastward propagation of the MJO across the Indian Ocean.

Multi Model MJO Phase Diagram


Not that it will matter much soon.
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1561. yoboi
Quoting Dull2012:


Must all of your posts on here be miniature Ph.D dissertations, my man?

ANYHOW, on that note, good evening, everybody! I hope you're all having a great Saturday night.


are ya being positive???
Member Since: August 25, 2010 Posts: 7 Comments: 2345

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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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