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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1247. Patrap
Heat Advisory

Statement as of 11:45 AM CDT on July 04, 2009

... Heat advisory remains in effect until 7 PM CDT this evening...

Hot conditions are expected to continue through this afternoon. Afternoon
high temperatures will range from the mid to upper 90s. These
temperatures will combine with moderately high humidity levels to
produce heat index readings ranging from 105 to 110 degrees this
afternoon.

Precautionary/preparedness actions...

A heat advisory means that a period of hot temperatures is
expected. The combination of hot temperatures and high humidity
will combine to create a situation in which heat illnesses are
possible. Drink plenty of fluids... stay in an air-conditioned
room... stay out of the sun... and check up on relatives and
neighbors.





Record Report

Statement as of 2:05 am CDT on July 04, 2009

... Record high temperatures tied at New Orleans International
Airport and Audubon Park...

the record high temperature of 98 degrees was tied at New Orleans
International Airport yesterday. The previous record was set in
1970.

The record high temperature of 98 degrees was tied at Audubon Park
yesterday. The previous record was set in 1969.
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Quoting Levi32:


The Climatology is July 10th.


Oh, okay, got it wrong.:) 1944 is an odd number to start off with. First radar perhaps.

And your 'ramblings' were very interesting, thanks KEH. :)
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Happy 4th to all! For those who have the the Pro Site at Accuweather, Joe Bastardi has a season update well worth the read.
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Quoting Cotillion:


Yes, quite, though I think I recall reading somewhere... that there are more German descendants than British. Most of those may have come later, I don't know for sure. But of course, there were no German colonies... at least I don't think there was.

John Locke is one of my favourite philosophers, for sure. His 'Second Treatise on Government' is well worth a read. (And not too long either, unlike Hobbes' Leviathan which is also very hard to understand because of the language, decipher almost.)
Majority by far (in Carolina) were English and African (hence the Gullah Culture). John Locke's ideals were introduced to Carolina by his good friend, Lord Ashley Cooper. Lord Ashley, had been a supporter of Cromwell turned Cavalier and bcame a supporter of the Merry Monarch and was one of the Lord's Proprietor of Carolina (we were not a colony yet - more of an investment opportunity).

I suppose since this is a Tropical Blog, I should hush up - thank you all for being so patient with my ramblings. Carry on!!
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1241. Levi32
Quoting Cotillion:


I think the long term average is June 15th, though. Though this is somewhat skewed by the really early starts such as in 2003 which bring the average back.

The end is about November 15th, also somewhat skewed by the late starts.


The Climatology is July 10th.
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Quoting AllStar17:
Subtropical Storm Laura from last season (9/29/08)



Invest 92L from earlier this season. Confuses me why it was not named....especially since they named Laura last year.



Because NHC has been unusually conservative this year. We may have had already 2 named storms by now.
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Quoting Levi32:


It's not even a late start. You guys are just used to early starts the last few years. Over half of all hurricane seasons don't even see their first named storm until after July 10th.


I think the long term average is June 15th, though. Though this is somewhat skewed by the really early starts such as in 2003 which bring the average back.

The end is about November 15th, also somewhat skewed by the late starts.
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Quoting KEHCharleston:
Since most of the settlers were English, with a smattering of Irish, German, French Huguenots (who had not fared well in France at the time), Sephardic Jews (who left Spain for religious freedom). So not really surprising that it was considered a distinct advantage to be an English Colony. Besides John Locke's ideals were superior, to anything else out there at the time. 'Governments rule by Consent of The People, not by Divine Right' (I am paraphrasing) A revolutionary idea - and one that later fueled the fight for Independence.


Yes, quite, though I think I recall reading somewhere... that there are more German descendants than British. Most of those may have come later, I don't know for sure. But of course, there were no German colonies... at least I don't think there was.

John Locke is one of my favourite philosophers, for sure. His 'Second Treatise on Government' is well worth a read. (And not too long either, unlike Hobbes' Leviathan which is also very hard to understand because of the language, decipher almost.)
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1237. Levi32
Quoting jrweatherman:
Late starters have shown on multiple occasions, they can be bad:

1977, 1983, 1992, 1998, 2002, 2004.


What abot the late starters that are not bad? Why ignore those years?


It's not even a late start. You guys are just used to early starts the last few years. Over half of all hurricane seasons don't even see their first named storm until after July 10th.
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Late starters have shown on multiple occasions, they can be bad:

1977, 1983, 1992, 1998, 2002, 2004.


What abot the late starters that are not bad? Why ignore those years?
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Quoting Cotillion:

Still surprised sometimes when people say they were glad to be under British, rather than French or Spanish rule.
Since most of the settlers (in Carolina) were English, with a smattering of Irish, German, French Huguenots (who had not fared well in France at the time), Sephardic Jews (who left Spain for religious freedom). So not really surprising that it was considered a distinct advantage to be an English Colony. Besides John Locke's ideals were superior, to anything else out there at the time. 'Governments rule by Consent of The People, not by Divine Right' (I am paraphrasing) A revolutionary idea - and one that later fueled the fight for Independence.
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1232. Levi32
Good morning all and Happy Independence Day!

Tropical Tidbit for July 4th, and a special video presentation on El Nino
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i officially proclaim 94L to be dead forever... the 10 knots wind shear will not last forever, the wind shear will increase to 20 knots by this evening



the blue are with the 10 right beside the whole bunch of red is where the storm is... there is a 20 right next to it... bye bye storm
Member Since: November 7, 2008 Posts: 0 Comments: 42
Quoting KEHCharleston:
Cotillion - Nothing needed. Just noticed that you were not present. BTW, we still have that crescent moon (second born son) on the SC flag - we still consider ourselves family. Besides if not for the British we would have been a Spanish or French colony (shudder). Actually, during the very early days of the colony, if it had not been for a hurricane that threw a combined Spanish-French force off course, it would have been a close call. So there is an example of a tropical storm that did a very good thing for the people of Carolina.

Aussie - Ahhh... I can understand your confusion.
SC joined the union before NC.


Thanks for noticing. :) Yeah, been busy lately, got back from Germany a few days ago.

Ah, I never knew there was any reference to us*; I know the Hawaiian flag contains the Union Jack though, which I was surprised to hear. Still surprised sometimes when people say they were glad to be under British, rather than French or Spanish rule.

* - That said, I can't say I know a lot about the state; I always forget that the capital of SC isn't Charleston. Heard from people it's a very nice place though, wouldn't mind visiting whenever I next cross 'the pond' in the distant future.
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CIMSS shear map has not updated since 5 AM EDT.
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1228. Patrap
I smell Mesquite..sniff,sniff


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Quoting AussieStorm:
Whats that off the coast of N/S Carolinas???


nothing yet

Member Since: November 7, 2008 Posts: 0 Comments: 42
75 degree water temp over the storm... if this storm does not become subtropical by tomorrow there will be 0 chance of it developing... although it has shear of just 10 knots it will be pretty difficult for it to develop. this may be good news but DO NOT TAKE THIS STORM LIGHTLY IT COULD POTENTIALLY BECOME A SUB TROPICAL SYSTEM.



the shear damage from the past few days can be seen as the center of circulation is very far away from the sever thunder storms
Member Since: November 7, 2008 Posts: 0 Comments: 42
Good surface rotation, (31N 39E). Based on SSTs and wind shear, it would need to get to ~20N to develop and continue heading west.

In addition, I think SFC circulation is going to do a loop and head back east.
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Cotillion - Nothing needed. Just noticed that you were not present. BTW, we still have that crescent moon (second born son) on the SC flag - we still consider ourselves family. Besides if not for the British we would have been a Spanish or French colony (shudder). Actually, during the very early days of the colony, if it had not been for a hurricane that threw a combined Spanish-French force off course, it would have been a close call. So there is an example of a tropical storm that did a very good thing for the people of Carolina.

Aussie - Ahhh... I can understand your confusion.
SC joined the union before NC.
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Quoting VAbeachhurricanes:
the thing is moving the direction it is moving, if it maintains the LLC, it will be moving into higher sst's and more favorable conditions

I dont know where your getting the track info from, but the official past track shows it moving east into lower temps.
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Quoting hurricane23:


It will be soon. Have fun.


how will it be dead the shear just dropped
Member Since: November 7, 2008 Posts: 0 Comments: 42
Whats that off the coast of N/S Carolinas???
Member Since: September 30, 2007 Posts: 9 Comments: 15935
1219. Patrap






Phew....another Cold Drink before I lite the pit.

Current Conditions

Uptown, New Orleans, Louisiana (PWS)
Updated: 10 sec ago
Scattered Clouds
92.3 F
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1218. IKE
Quoting AllStar17:


I would definitely agree with Dr. Masters on the "real" season beginning August 1st. And, I said some bloggers are writing this season off, I did not say you were, and it has been a yawner thus far, but everyone needs to not look at it as a yawner for the whole season, as it will not stay that way. And, just a question, how can I get an avatar?


I didn't get the feeling you were really talking about me.

I'll have to see how you download an avatar. I don't remember, off hand.
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Quoting KEHCharleston:
1209. CotillionI was asking about you yesterday. Glad to see you on the blog.


Why, hello! Good to see you. How are things? Anything you needed?
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1215. Patrap
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1209. Cotillion!!!
I was asking about you yesterday. Glad to see you on the blog.
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the thing is moving the direction it is moving, if it maintains the LLC, it will be moving into higher sst's and more favorable conditions
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Quoting IKE:



Those that are calling it that are wrong. I've said it's been a "yawner" so far and it has.

It won't continue. Dr. Masters has said August 1st is the beginning of the real season and I believe him.

I do think this year will be slower, as I belated picked 10-4-2 as totals. I thought about picking 9 as a total, but I'll stay with 10.


I would definitely agree with Dr. Masters on the "real" season beginning August 1st. And, I said some bloggers are writing this season off, I did not say you were, and it has been a yawner thus far, but everyone needs to not look at it as a yawner for the whole season, as it will not stay that way. And, just a question, how can I get an avatar?
Member Since: June 29, 2009 Posts: 13 Comments: 5311
Quoting Cotillion:
The analog tracks map looks like it has been sabotaged by a 2 year old and their first felt tip.


It would have been better if they used different colors...lol
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Also, is the surface circ. moving south, and is the mid level circulation is moving in tune with the convection? I can certainly tell the SFC circulation is moving south. Is the storm still stacked?
Member Since: June 29, 2009 Posts: 13 Comments: 5311
The analog tracks map looks like it has been sabotaged by a 2 year old and their first felt tip.
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Quoting VAbeachhurricanes:
interesting that the NHC says 94L is moving east, when this sat shows it is no doubt moving SW.
Link


Very interesting.....
It is clearly moving south and away from the convection. If it moved ENE, it would still be at least near the convection.
Member Since: June 29, 2009 Posts: 13 Comments: 5311
Models:


Analog tacks:


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Happy Independence (from us) Day, Americans. ;)
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.
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Quoting KEHCharleston:
Glad you put that 'N/S' in front of Carolinas, cause Press may be lurking!! However it should be 'S/N'

but isn't north before south on a compass. and in the alphabet too
Member Since: September 30, 2007 Posts: 9 Comments: 15935
1203. IKE
Quoting hurricaneseason2006:
I started noticing how we all saw a change in the tune of some bloggers by the time 93L was done and June had ended. I remember IKE used to favor development on the GFS back early in June in the Western Caribbean and as soon June ended he just sounds disappointed and upset June was quiet. Imagine the things he says now after he regarded himself as a "wishcaster".


Yeah...the GFS has been proven wrong. I did jump on their bandwagon. I was wishcasting 93L to me because it's been so dry.

I'm gonna tell you like I told the other blogger...I've got too many other things to really get worried about like my health. If you want I'll tell you the 4 year story in a personal mail.

Disappointed? Upset? LOL.

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interesting that the NHC says 94L is moving east, when this sat shows it is no doubt moving SW.
Link
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Im going to say that 94L will not develop due to the fact it can not maintain convection near the center.

It did look good earlier today though.

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Quoting AussieStorm:
I remember Dr. Masters saying there is a higher chance of a storm developing in the GOMEX or off the coast of FLA. and N/S Carolina's this season
Glad you put that 'N/S' in front of Carolinas, cause Press may be lurking!! However it should be 'S/N'
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Late starters have shown on multiple occasions, they can be bad:

1977, 1983, 1992, 1998, 2002, 2004.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1198. IKE
Quoting AllStar17:


Good point, and it is only July 4th, and some bloggers are calling this season a bust, very confusing to me.



Those that are calling it that are wrong. I've said it's been a "yawner" so far and it has.

It won't continue. Dr. Masters has said August 1st is the beginning of the real season and I believe him.

I do think this year will be slower, as I belated picked 10-4-2 as totals. I thought about picking 9 as a total, but I'll stay with 10.
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About

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