July hurricane outlook

By: Dr. Jeff Masters , 7:26 PM GMT on July 02, 2009

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Atlantic tropical cyclone activity typically picks up a bit during the first half of July. Since the current active hurricane period began in 1995, seven of 14 years (50%) have had a named storm form during the first half of July. The busiest first half of July occurred in 2005, when three hurricanes formed. These included Hurricane Dennis and Hurricane Emily--the strongest hurricanes ever observed so early in the season. As seen in Figure 1, most of the early July activity occurs in the Gulf of Mexico, Western Caribbean, and Carolina waters. However, a few long-track "Cape Verdes" hurricanes begin to occur. These are spawned by tropical waves that come off the coast of Africa. Tropical waves serve as the instigators of about 85% of all major hurricanes. Last year's Hurricane Bertha was one such rare early July Cape Verdes hurricane. Bertha's 120 mph winds made it the sixth strongest early-season Atlantic hurricane on record. Bertha also set the record for farthest east formation as a tropical storm, hurricane, and major hurricane, so early in the season.


Figure 1. Tracks of all tropical storms and hurricanes 1851 - 2006 that formed July 1-15. North Carolina and the Gulf of Mexico coast from the Florida Panhandle to Texas are the preferred strike locations. Oddly, the Florida Peninsula has been struck by only two storms that formed in the first half of July.

Sea Surface Temperatures
Sea Surface Temperatures (SST) anomalies have warmed slightly over the past two weeks, but are close to average over the tropical Atlantic between Africa and Central America (Figure 2). These are the are the coolest SST anomalies we've seen since 1994. The strength of the Azores-Bermuda high has been near average over the past two weeks, driving near-average trade winds. Stronger-than-average trade winds were observed through most of the period November 2008 - May 2009, which helped cool the tropical Atlantic substantially. Strong winds mix up colder water from the depths and cause greater evaporative cooling. The latest 2-week run of the GFS model predicts continued average-strength trade winds through mid-July, so SSTs should remain near average during this period.

Typically, July tropical storms form over the Gulf of Mexico, Western Caribbean, and Gulf Stream waters just offshore Florida. SSTs are about 1.0°C above average for this time of year in the Gulf of Mexico, but near average elsewhere. July storms typically 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. There will be one or two fronts moving off the U.S. coast over the next two weeks, and we will need to watch these for development. Wind shear is too high and SSTs are usually too cold in July to allow African tropical waves to develop into tropical storms. African tropical waves serve as the instigators of about 85% of all major hurricanes,

Figure 2. Sea Surface Temperature (SST) departure from average for July 2, 2009. SSTs were near 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
El Niño conditions continue to amplify over the tropical Eastern Pacific. Ocean temperatures there rose 0.5°C over the past two weeks, and are now 0.45°C above the threshold for El Niño, according to the Australian Bureau of Meteorology (Figure 3). NOAA's Climate Prediction Center issued an El Niño Watch in early June, saying "that conditions are favorable for a transition from neutral to El Niño conditions during June - August 2009". The pattern of changes in surface winds, upper-level winds, sea surface temperatures, and deeper water heat content are all consistent with what has been observed during previous developing El Niños, and latest set of mid-June runs of the El Niño computer models are almost universally calling for El Niño conditions to become well-established for the peak months of hurricane season, August - October. It is likely that Atlantic hurricane activity will be suppressed in 2009 due to the strong upper-level winds and resulting wind shear an El Niño event usually brings to the tropical Atlantic.


Figure 3. 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 June 28, 2009, SSTs in the Niño 3.4 region had risen to 0.95°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: Australian Bureau of Meteorology.

Wind shear
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's band of strong high-altitude winds is the main source of wind shear in July over the Atlantic hurricane breeding grounds, since the jet is very active and located quite far south this time of year.

The jet stream over the past two months has been locked into a pattern where a southern branch (the subtropical jet stream) brings high wind shear over the Caribbean, and a northern branch (the polar jet stream) brings high wind shear offshore of New England. This often leaves a "hole" of low shear between the two branches off the coast of North Carolina, which is where Tropical Depression One formed at the end of May.

The jet stream is forecast (Figure 4) to maintain this two-branch pattern over the coming two weeks. This means that the waters offshore of the Carolinas are the most likely place for a tropical storm to form during this period.


Figure 4. Wind shear in m/s between 200 mb and 850 mb, as forecast by the 06Z July 02, 2009 run of the GFS model. The position and strength of the subtropical jet stream is forecast to change little over the next two weeks, and this jet will bring high wind shear to the Caribbean and Gulf of Mexico into mid-July. There will at times be a region of low shear between the polar jet (northern set of arrows on the plots) and the subtropical jet, allowing for possible tropical development off the coast of North Carolina. Wind speeds are given in m/s; multiply by two to get a rough conversion to knots. Thus, the red regions of low shear range from 0 - 16 knots.

Dry air and African dust
June and July are the peak months for dust coming off the coast of Africa, and the Saharan dust storms have been quite active over the past month. Expect dust from Africa to be a major deterrent to any storms that try to form between Africa and the Lesser Antilles Islands in July.

Steering currents
The steering current pattern over the past few weeks has not changed much, and is typical for June and 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. At present, it appears that the coming two weeks will maintain the typical July pattern, bringing many troughs of low pressure off the East Coast capable of recurving any July storms that might form. 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 2006 steering current pattern that recurved every storm out to sea--or the unfavorable 2008 pattern, that steered Ike and Gustav into the Gulf of Mexico.

Summary
Recent history suggests a 50% chance of a named storm occurring in the first half of July. Given that none of the computer models are forecasting tropical storm formation in the coming seven days, and SST and wind shear patterns look pretty average, I'll go with a 20% chance of a named storm forming during the first half of July.

Vote for Mike Theiss as an Antarctica blogger
Extreme weather photographer Mike Theiss, who wrote our Ultimate Chase photography blog for two years until a new job took him to South America, wants your help. He's entering a Quark Expeditions competition to receive an expense-paid 2-week trip to Antarctica, where he will do some intensive photography and blogging. In order to go, he needs the votes to show that he's a popular blogger. So, if you liked his posts while he was blogging for wunderground, and want to see him blog for wunderground during this potential Antarctica voyage, go to http://www.blogyourwaytoantarctica.com/blogs/view /220 and cast a vote. It takes about 3 minutes navigate through the registration and voting process. Mike will be back chasing hurricanes this August, and has promised to post his excellent storm photos on wunderground should we help him secure the Antarctica gig.

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

Jeff Masters

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support barometer bob show log in now live show
Member Since: Posts: Comments:
Quoting hunkerdown:
It is really sad when the most popular quote on this blog this year is "lol".

Y'all just be careful, you never know when major hurricane LOL will be bearing down on your a$$.


One should always prepare for the worst case senario in Hurricane prone areas. If you don't, you only impact yourself. Being prepared provides confidence and mitigates fear to a degree.

Ask yourself,,,, Am I ready? Do I have a plan? Do I have the importatnt documents safe?

OK, you all get it. If you need help, try this site " OneStorm.com"

This is posted on WU, and not spam, or check out the many available blogs, Patrap's or many others.

After all, it is you, counting on you, right :)


Atmoaggie, I think that is called cyberstudder.
Member Since: June 12, 2005 Posts: 6 Comments: 8188
Oss, sometime one system can wrap in another's vorticity and build itself. Some thoeries posed that Katrina did just that.

Dang did double that previous post. Sorry. Modify not possible.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Another pretty vigorous boomer rollinng into St Tammany.

Cable went down about 30 minutes ago...cannot link or post images.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Another pretty vigorous boomer rollinng into St Tammany.

Cable went down about 30 minutes ago...cannot link or post images.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
It is really sad when the most popular quote on this blog this year is "lol".

Y'all just be careful, you never know when major hurricane LOL will be bearing down on your a$$.
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What is up with this item also?

The loop shows the prior one dissapearing in that spot, can they actually grab energy from each other ?



loop
Member Since: June 12, 2005 Posts: 6 Comments: 8188
Quoting tropicfreak:


Your kidding right.
No, he is dead seious...the folks at the NHC have packed their bags and headed home.

Everyone is on their own as there is no expected activity in 2009.
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...///
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Quoting Ossqss:
Well, you just don't know what will show up in YouTube when you type something. This is just amazing and related to a certain degree to the season and previous posts. I just could not believe my eyes. Nothin else significant happening anyhow.

This by no means is disrespectful to anyone including OZ, just quite interestingly funny.

Fainting Goats


Umm.... LMAO
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Well, you just don't know what will show up in YouTube when you type something. This is just amazing and related to a certain degree to the season and previous posts. I just could not believe my eyes. Nothin else significant happening anyhow.

This by no means is this intended to be disrespectful to anyone including OZ, just quite interestingly funny.

Fainting Goats
Member Since: June 12, 2005 Posts: 6 Comments: 8188
here is a link to barometer bob show

Link
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lol
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Quoting Ossqss:


Right next to CycloneOZ in HD, LoL


LOL
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Quoting Ossqss:


Right next to CycloneOZ in HD, LoL



lol
Member Since: June 29, 2009 Posts: 13 Comments: 5315
Quoting AllStar17:


Jim Cantore just fainted


Right next to CycloneOZ in HD, LoL
Member Since: June 12, 2005 Posts: 6 Comments: 8188
A review of today's El Niño Modoki study.
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Quoting hurricane2009:
I think the comparison to 1977 has MUCH more to do with the inactivity in the other basins and has very very little to do with the Atlantic.
correct thats what i'm lookin at and 77 is the only season that had such occurences in 77 they could not even give a reason for all basins having a low seasonel count official cause is unknowned at the time and as for the cat five tearing up mexico the loss of life was only 10 because it made landfall in a low populated area
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Quoting hurricane2009:


I wish they would put up different message, how about these:

"Here invest, here boy *whistle*"
"Wait is that an invest!!, nope just some clouds, sigh."



lol lol lol
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I was just testing y'all. LOL
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Quoting tropicfreak:


Your kidding right.

not kidding
Member Since: June 29, 2009 Posts: 13 Comments: 5315
Quoting hurricane2009:
Breaking News:

The National Hurricane Center has cancelled the 2009 Hurricane Season due to lack of activity during times that there usually is no activity (yea get that one). In reaction a loud collective sigh of relief is heard by the astronauts in space as people who live along the coast all go back to Home Depot and attempt to send back their plywood.


Your kidding right.
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Oh this is a keeper.

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Quoting KEEPEROFTHEGATE:
it happen before 456 in 1977 lowest worldwide cyclone activity recorded in all basins the atl that year had only 6 storms the entire sesason and 3 of them occur in sept of that year
Yes, but of the 6 only 1 never made it to hurricane status and that was the last 1 Freida.
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1977 wasnt exactly docile. Anita tore up the Mexican coastline.

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Quoting hurricane2009:
Breaking News:

The National Hurricane Center has cancelled the 2009 Hurricane Season due to lack of activity during times that there usually is no activity (yea get that one). In reaction a loud collective sigh of relief is heard by the astronauts in space as people who live along the coast all go back to Home Depot and attempt to send back their plywood.


Jim Cantore just fainted
Member Since: June 29, 2009 Posts: 13 Comments: 5315
Quoting Weather456:
I love the Navy TC site, first it was

Nary an invest stirred no matter where one look

and now

Where, oh where, might the next Invest begin?

This has to be one of the slowest summers for the Northern Hemisphere and especially surprising in the WPAC.
it happen before 456 in 1977 lowest worldwide cyclone activity recorded in all basins the atl that year had only 6 storms the entire sesason and 3 of them occur in sept of that year
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Hey patrap, hope that little sea-breeze explosion dosent hit you guys on the southshore so hard. Had what I can only call a microburst.. one tree on the house, took out the DTV dish, and it looks like a large power line out at the bayou's down. Havent heard this many generators humming since K.
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Well that's a wrap, guess we'll meet again June 2010, same place, same time.
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Quoting tropicfreak:


A pretty big blowup of convecton on the coast of Nicaragua. I would also keep an eye on this.


That is just being enhanced by an ULL to the NW, but the other area you showed does bear watching
Member Since: June 29, 2009 Posts: 13 Comments: 5315
Quoting vortfix:



LOLOLOLOLO!

Wassup Keep??

I find it hard to believe that anything could happen in the Caribbean for at least the next 4-5 days the way the features shape up.

with the way things are going it may be awhile vort which is not a bad thing we don't need em anyway better off without em no death no destruction is a good thing as far as iam concearn i have a feeling we could see a repeat of 77 in which all basins worldwide had a very reduce cyclone season and so far thats is just the case except for some early teasers in the atl
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Quoting StormW:


You didn't miss anything...just jokin around...something we kick around here now and then when it's boring.

Haha. i thought it was a joke to play around with the on again off again..but just checking....=D thanks
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Is the storm in MS a Mesocyclone? The storm appears to be rotating itself.
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I love the Navy TC site, first it was

Nary an invest stirred no matter where one look

and now

Where, oh where, might the next Invest begin?

This has to be one of the slowest summers for the Northern Hemisphere and especially surprising in the WPAC.
Member Since: Posts: Comments:
..
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Quoting Patrap:

526
WUUS54 KLIX 022345
SVRLIX
LAC103-030030-
/O.NEW.KLIX.SV.W.0136.090702T2345Z-090703T0030Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE NEW ORLEANS LA
645 PM CDT THU JUL 2 2009

THE NATIONAL WEATHER SERVICE IN NEW ORLEANS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
WEST CENTRAL ST. TAMMANY PARISH IN SOUTHEAST LOUISIANA...
THIS INCLUDES THE CITIES OF...MANDEVILLE...COVINGTON...

* UNTIL 730 PM CDT

* AT 643 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS
OF 60 MPH. THIS STORM WAS LOCATED NEAR COVINGTON...AND MOVING
SOUTH AT 15 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
MADISONVILLE BY 705 PM CDT...
MANDEVILLE BY 710 PM CDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS STORM. IF YOU ARE IN ITS PATH...PREPARE
IMMEDIATELY FOR DAMAGING WINDS...DESTRUCTIVE HAIL...AND DEADLY CLOUD
TO GROUND LIGHTNING. PEOPLE OUTSIDE SHOULD MOVE TO A SHELTER...
PREFERABLY INSIDE A STRONG BUILDING BUT AWAY FROM WINDOWS.


TORNADO WARNING
MSC045-030030-
/O.NEW.KLIX.TO.W.0046.090702T2354Z-090703T0030Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE NEW ORLEANS LA
654 PM CDT THU JUL 2 2009

THE NATIONAL WEATHER SERVICE IN NEW ORLEANS HAS ISSUED A

* TORNADO WARNING FOR...
SOUTHERN HANCOCK COUNTY IN SOUTHERN MISSISSIPPI...

* UNTIL 730 PM CDT

* AT 652 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR
PEARLINGTON...OR 8 MILES WEST OF WAVELAND...MOVING SOUTH AT 5 MPH.

* THIS STROM IS NOT EXPECTED TO AFFECT ANY LARGE POPULATED AREAS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THE SAFEST PLACE TO BE DURING A TORNADO IS UNDER A WORKBENCH OR OTHER
PIECE OF STURDY FURNITURE. SEEK SHELTER ON THE LOWEST FLOOR OF THE
BUILDING IN AN INTERIOR HALLWAY OR ROOM SUCH AS A CLOSET. USE
BLANKETS OR PILLOWS TO COVER YOUR BODY AND ALWAYS STAY AWAY FROM
WINDOWS.

IF IN MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET INSIDE A
SUBSTANTIAL SHELTER. IF NO SHELTER IS AVAILABLE...LIE FLAT IN THE
NEAREST DITCH OR OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR HANDS.
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199. beell
A vote for Mike,here
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A pretty big blowup of convecton on the coast of Nicaragua. I would also keep an eye on this.
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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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