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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Quoting hunkerdown:
ULLs are not drought busters. ULLs are not a given to produce any rainfall.

If people want to know specific questions, and I am not sure that thunder did, maybe it should have been asked if the ULL will bring any needed relief to the drought stricken areas of Texas. Or maybe even check in with the local NWS.


An upper low in Texas would almost certainly result in afternoon showers given their climate, and I knew why he asked his question without him even mentioning the drought.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
well, the NWS says there is a chance the ridge will set up far enough north that se Tx could get some seabreeze showers, but going on persistence they doubt it.
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Quoting thunderblogger:
378.

Levi, thank you. The rain is what we need in a desperate way in Texas, and I know that ULL is capable enhancing that fact. But I guess patience and optimism is our best friend still......
no significant chance of rain for 10 days if your in the SeTx area.
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Quoting hurricane2009:


ECMWF has been hinting at a monster storm developing out there


Yeah and I can't tell ya how much I'm routing for a monster fish storm to form out there so I and everyone else here have something to do lol.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
maybe when that wave gets to the east Pac
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377. believe it or not, unlike moderators that would ban those with skeptical viewpoints, I'm NOT trying to suppress debate--rather, I'm trying to foster it. of course, the prerequisite for debate is that either side is open to the others' viewpoint despite apparently contradictions to one's own view....
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Quoting errantlythought:
356.

Covington


Me too. Off Harrison ave. We had a little wind, but yours sounds a lot worse.

I see Covington/Mandeville made the SPC wind reports.
http://w1.spc.woc.noaa.gov/climo/reports/today.html
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Quoting Levi32:


It matters when you're in a water shortage and you need rain.
ULLs are not drought busters. ULLs are not a given to produce any rainfall.

If people want to know specific questions, and I am not sure that thunder did, maybe it should have been asked if the ULL will bring any needed relief to the drought stricken areas of Texas. Or maybe even check in with the local NWS.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
378.

Levi, thank you. The rain is what we need in a desperate way in Texas, and I know that ULL is capable enhancing that fact. But I guess patience and optimism is our best friend still......
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on the remark of the GOP hurricane2009... I totally disagree with you. This administration will do good to make it through its 4 years... civil unrest is already brewing here in the South and we aren't even getting hit by the economic downfall.. When all these people see the taxes sky rocket due to the outlandish spending then American government will take a turn... If you study American Politics which it sounds like some of you have and some of you clearly haven't then you will notice that there is typically a swing of parties then the country goes through a reformation after the swing of parties proved to be the wrong choice. Could we see this? its possible.. since the GW people like trends it would be a good one to look at.
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Quoting vortfix:
ECMWF/GFS 8-10 day 500mb means still showing the east coast trough in a position to cause trouble off the SE coast during the next 2 weeks. Keep an eye on that area.


Yes!
And that would be about it regarding formation.
Nothing can happen in the Carib for the next 5 days or so.



The east Pacific will likely have attention by next week with a possible storm forming there from all that building heat.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting vortfix:
ECMWF/GFS 8-10 day 500mb means still showing the east coast trough in a position to cause trouble off the SE coast during the next 2 weeks. Keep an eye on that area.


Yes!
And that would be about it regarding formation.
Nothing can happen in the Carib for the next 5 days or so.

it may even be 7 to 10 before anything vort
Member Since: July 15, 2006 Posts: 178 Comments: 56140
Strong Wave......

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356.

Covington
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Quoting RainyEyes:
well, I see it is an active and viscious night on here as usual...hello all!


JOin in but where some very high boots...LOL
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364. that's great!...as long as those receiving the funds won't be pressured to produce a desired result for POLITICAL means! as long as the US Federal Government is involved (a political institution as long as I've been alive), I would assume that those receiving the funds will be pressured to produce a desired result, regardless of what the data say....
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Quoting hunkerdown:
does it really matter ? Now we are discussing ULLs ? That is why political, sports, and other random comments are being posted.


It matters when you're in a water shortage and you need rain.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting thunderblogger:
Does anyone know where the ULL in the western Carribean will end up? Texas coast? Or further south?
does it really matter ? Now we are discussing ULLs ? That is why political, sports, and other random comments are being posted.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
ECMWF/GFS 8-10 day 500mb means still showing the east coast trough in a position to cause trouble off the SE coast during the next 2 weeks. Keep an eye on that area.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Quoting thunderblogger:
Does anyone know where the ULL in the western Carribean will end up? Texas coast? Or further south?


It should continue NW into the NW Caribbean until it buts up against the upper high in the NW gulf. That will deflect it SW over central America as it dissipates.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting pearlandaggie:
352. that's actually a GREAT question. what would you think if the data has been so heavily messaged that a warming trend appears, regardless of whether or not it actually occurred? what if those sensors showing the warming trend were located in increasingly urbanized areas and the calculations to "correct" for the urbanization were too low? what kind of trend would you expect to see?


Additionally, what if the data from the early 1900s were to be massaged downward from the raw data? It sure would look like warming if one were to suddenly make it "cooler" from 1900 to 1940.

All of the above (my statement and plandag's) is true. Our caretakers of the historical observations have performed a disgusting bit of "science" to satisfy something.
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Member Since: July 15, 2006 Posts: 178 Comments: 56140
Quoting hurricane2009:


This is a weather site, not a political site. Dont need the smart remarks really.
oh, ok then...boy it was hot here today in Boynton Beach, although not has hot as it has been or coul dbe. Then it rained. Then it stopped raining. Now its muggy out, and the mosquitos are rampant (uh oh, are mosquitos weather related ???).

We all know this is mostly a tropical weather blog, with some severe weather interests. When there are no occurrances, people tend to babble about whatever they feel or bicker and fight, both of which have been common here lately.
Member Since: August 15, 2008 Posts: 0 Comments: 2515
There is not a lot going on weather wise so the blog tends to turn to chatter... keeps people at the blog which in turn earns the website its money to stay open by ad revenue...

hence when weather is slow idle chatter is good... trust me if something pops up we gonna be all over it... :)
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Does anyone know where the ULL in the western Carribean will end up? Texas coast? Or further south?
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Remember, the reaction of the Earth to the Sun, is the primary driver of all of our weather and existence. Like it or not, that's the fact. The rest is 2ndary and trivial. L8R



SPACE WEATHER
Current conditions
Solar wind
speed: 381.6 km/sec
density: 0.5 protons/cm3
explanation | more data
Updated: Today at 0226 UT
X-ray Solar Flares
6-hr max: A0 2355 UT Jul02
24-hr: A0 2355 UT Jul02
explanation | more data
Updated: Today at: 2355 UT

Daily Sun: 02 July 09

The sun is blank, no sunspots. Credit: SOHO/MDI


Sunspot number: 0
What is the sunspot number?
Updated 01 July 2009

Spotless Days
Current Stretch: 7 days
2009 total: 141 days (77%)
Since 2004: 652 days
Typical Solar Min: 485 days
explanation | more info
Updated 01 July 2009
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Quoting hurricane2009:


This is a weather site, not a political site. Dont need the smart remarks really.


What ever do you mean?

LOL. Really, you were dishing it out earlier. Can't take it? (tongue-planted-firmly-in-cheek)
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One thing I'll say is this administration will be investing more in science then any time in my lifetime(31yrs)....and that has to be a good thing for the earth,every american that can should have there own gardens(organic) and recycle for a start,there would be alot less garbage and would free up some money to save,IMO...
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Quoting RainyEyes:
well, I see it is an active and viscious night on here as usual...hello all!


I just got here too lol. Hi there.
----------------------------------------------

Heat continuing to build in the Eastern Pacific.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
352. that's actually a GREAT question. what would you think if the data has been so heavily messaged that a warming trend appears, regardless of whether or not it actually occurred? what if those sensors showing the warming trend were located in increasingly urbanized areas and the calculations to "correct" for the urbanization were too low? what kind of trend would you expect to see?
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SO much for talking about the weather. :(
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Quoting hurricane2009:


Politics dont belong on this site period, this site has been taken over by them. It is really sad what the site has become when there are more political blog then there are weather blogs


What weather? It is somewhere between boiling and absolute zero out. And there is likely H2O in all 3 phases somewhere on the ground or overhead. Anything else to talk about? No.
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well, I see it is an active and viscious night on here as usual...hello all!
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Quoting atmoaggie:


And any provision to have "fees", "charges", "buy and sell credits" will cost money. Government mandated expenses still quack and walk like a duck. Still is a tax. And all money flows from wallets...not corporations. Some corporations able to do so will just pass along costs to you, hurricane_n00b. Others will simply reduce their payrolls. Sounds wonderful.


Well said, it all comes back to our wallets, period.
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Quoting errantlythought:
330.

I'm curious how less than a decade of marginal cooling causes question to be cast on 140 years of relatively rapid warming.


Hey there. Where you at to get such a downburst earlier?

Oh, and 140 years of numbers? Not very good measurements, that. Has been shown to be a faulty set of data over and over again.
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343. whatever, dawg. politics DO BELONG ON THIS BLOG when those political positions, regardless of scientific data, advance the positions of those that would reduce this country to a socialistic state! ban me if you must, but i and my opinions will be back to sound the consequences of such willful negligence.
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Quoting Ossqss:
This basic premise becomes invisible in times like this. The government is not a revenue generating entity. They use money we give them. The more they spend the more we owe. It doesn't come from anyone else but you. You are and will always be part of the equation. We must spend wisely.


And any provision to have "fees", "charges", "buy and sell credits" will cost money. Government mandated expenses still quack and walk like a duck. Still is a tax. And all money flows from wallets...not corporations. Some corporations able to do so will just pass along costs to you, hurricane_n00b. Others will simply reduce their payrolls. Sounds wonderful.
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330.

I'm curious how less than a decade of marginal cooling causes question to be cast on 140 years of relatively rapid warming.
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Quoting hurricane2009:


Politics dont belong on this site period, this site has been taken over by them. It is really sad what the site has become when there are more political blog then there are weather blogs


Yeah I agree. That's what happens when a site gets to a certain amount of traffic. Seriously I am flagging political posts in this blog you guys.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting pearlandaggie:
342. what??? OMG!!!!! the government doens't PRODUCE anything???? they ONLY TAKE FROM THOSE THAT DO??? what kind of school of philosophy did you attend? :)


Tell me what they do that the taxpayers don't pay for?
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Hey if we are on the government kick... lets go ahead a kick everyone out of government and start over.. put good ol people in there not politicians.. put people in who know about real life experience, who use common sense and have values. The degradation of American government can be articulated best by this "no values"... when congressmen/women start selling their vote to get something else done for them then what has our government become.. I know this has happened for a long time, shoot we even have a name for it "pork barreling" but wow! Everyone needs to get out in their community... go to the Tea Parties, trust me its not a Republican thing its a get back to the basics of America thing.

anyway off soap box... Looks like the wave around 53w has somewhat fallen apart. It looked good today but as usual didn't hold up. maybe tomorrow it can revamp a little.
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342. what??? OMG!!!!! the government doens't PRODUCE anything???? they ONLY TAKE FROM THOSE THAT DO??? what kind of school of philosophy did you attend? :)
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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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