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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Hey all, I've started a blog on here. As a lifelong weather and climate enthusiast, I've decided to start a blog which will document the changes in climate over time right here in the Midwest.

All are welcome to chime in, regardless of your stance on climate change. I'm not going to use the blog to discuss the policy implications or advocate for or against action on climate change. I don't even care whether or not you believe man is the cause of the observed climate change. Instead, the focus is going to be on documenting the changes in the climate with a particular focus on the Midwestern U.S.

My first blog looks at how temperatures in Detroit and Chicago this year stack up against 1961-1990 normals in those cities, as well as the 1961-1990 normals in St. Louis and Cincinnati/Northern Kentucky. In Detroit, through July 15, the mean has been 52.7F. This is 7.3F above the 1961-1990 normal for the city during the same period, and 2.0F above the 1961-1990 normal in Cincinnati/Northern Kentucky for the same period. In Chicago, through July 15, the mean has been 53.9F. This is 8.1F above the 1961-1990 normal for the city, and 0.3F above the 1961-1990 normal for St. Louis for the same period!
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Quoting Skyepony:
0808 PM FLASH FLOOD AUSTIN 30.31N 97.75W
07/15/2012 TRAVIS TX BROADCAST MEDIA

FLASH FLOODING AND HIGH WATER RESCUES AT SEVERAL
LOCATIONS IN AUSTIN TRAVIS TX PUBLIC

6 BOATS OF UNKNOWN SIZE FLIPPED OVER DUE TO HIGH WINDS
AT EMERALD POINT MARINA ON LAKE TRAVIS


Oh, man. Not good. We've had downdrafts over the last month - one exceptional where I heard 30 people screaming down at the marina - and unidentifiable people surfacing since then. I feel like I should go over there and help
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Quoting PlazaRed:

We should do a poll on the Olympic this that's going to clog up everything at the end of the month. It could be the wettest Olympics ever!
On the bright side, the beach volleyball should be fun. Especially if a cold wind sets in.
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2358. Patrap
Fabio


RGB Image

01:00 UTC

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2357. WunderAlertBot (Admin)
JeffMasters has created a new entry.
Does anyone get an error message when going to NWS Miami?
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2355. Patrap
Fabio

RainBow Top Image

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2354. yoboi
Quoting Grothar:
We are getting a lot of thunder and lightning along the coast right now.




can ya post the radar for ya coast???
Member Since: August 25, 2010 Posts: 7 Comments: 2532
2353. Skyepony (Mod)
0808 PM FLASH FLOOD AUSTIN 30.31N 97.75W
07/15/2012 TRAVIS TX BROADCAST MEDIA

FLASH FLOODING AND HIGH WATER RESCUES AT SEVERAL
LOCATIONS IN AUSTIN



0745 PM FLASH FLOOD ROUND ROCK 30.52N 97.67W
07/15/2012 WILLIAMSON TX EMERGENCY MNGR

EMERGENCY MANAGER REPORTED NUMEROUS ROADS CLOSED IN
ROUND ROCK DUE TO FLOODING. HOME EVACUATIONS AND HIGH
WATER RESCUES OCCURRING



0525 PM TSTM WND DMG 4 ESE LAGO VISTA 30.43N 97.94W
07/15/2012 TRAVIS TX PUBLIC

6 BOATS OF UNKNOWN SIZE FLIPPED OVER DUE TO HIGH WINDS
AT EMERALD POINT MARINA ON LAKE TRAVIS
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2352. Grothar
Quoting GeoffreyWPB:


Wait till tomorrow.


What's the forecast for tomorrow?
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Quoting hurricane23:


Or central America :0)
It is still a strong forecasted high and not good for us if/when a storm forms.
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2350. Grothar
We are getting a lot of thunder and lightning along the coast right now.

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2349. KEEPEROFTHEGATE (Mod)
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Quoting Tropicsweatherpr:


pr, I see at least 3 circulations in the loop. Time is drawing closer for us to start watching the MDR area.


Couple of weeks and we will be facing reality....
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Quoting hurricane23:


Or central America :0)


U.S. is more likely than CA
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2344. JLPR2
Quoting sunlinepr:


That is one suspicious spin.
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2343. Grothar
Quoting redwagon:

All three five spins are very nice. Especially mine over Centex. But I'm really interested in that one off the GA/SC coast - might it spin up in this 'down' MJO?


Yes, it could. Some models have been hinting at that. I just wish you good MOJO.
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Quoting sunlinepr:


pr, I see at least 3 circulations in the loop. Time is drawing closer for us to start watching the MDR area.
Member Since: April 29, 2009 Posts: 75 Comments: 14781
2341. Grothar
Quoting GeoffreyWPB:
Went to a B-Day party today. A lot of red balloons. They wanted a 100, but one popped. Since, the blog is slow, I wish there was a video I could post to express how I feel.


Not unless you want to get bannded.
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Quoting redwagon:

All three five spins are very nice. Especially mine over Centex. But I'm really interested in that one off the GA/SC coast - might it spin up in this 'down' MJO?


As I learned in Tropical Weather Rehab...One day at a time.
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2338. Grothar
Quoting TropicalAnalystwx13:

That's 'cause they're in a high pressure environment, Gro. You should know that. ;-)


I know that you little..... :)
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Went to a B-Day party today. A lot of red balloons. They wanted a 100, but one popped. Since the blog is slow, I wish there was a video I could post to express how I feel.
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Quoting Grothar:


I implied all three of them. Just too tired to write, nice spin on all three.

All three five spins are very nice. Especially mine over Centex. But I'm really interested in that one off the GA/SC coast - might it spin up in this 'down' MJO?
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Quoting Grothar:


That doesn't necessarily mean TS's. A lot of times a string of lows can form above a strong high pressure system. Not unusual this time of year. They don't reflect very low pressures on them.
It is still multiple lows tropical or not. We will have to wait and see if it even opans out.
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this depression has strange form
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Quoting wxchaser97:
Good thing a cv storm shouldn't form in the next week or so:

The high would push it into us.


Or central America :0)
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2332. Grothar
Quoting washingtonian115:
Can anyone see my comment?.


No.
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2330. Skyepony (Mod)
South Africa~ Rescue workers evacuated more than 2000 people as heavy rains and snow battered southern parts of South Africa over a freezing weekend. The precipitation had cut off all road links between economic hubs Johannesburg and Cape Town, causing a huge traffic backlog, though main highways linking the north and south of the country were reopened Sunday afternoon, said Road Traffic Management Corporation spokesman Ashraf Ismail. Dozens of trucks had been stuck on the routes after heavy snow had closed them down since Saturday. Soon after traffic was opened, around 500 trucks that had been held up in Johannesburg by the closures started the trek toward Cape Town in the south, Mr Ismail said. Over 100 millimetres of rain fell over the area in three days, with more heavy showers predicted through Sunday night. Thousands of people were moved to community centres as floods hit southern city Port Elizabeth, said municipal spokesman Kupido Barron. "We assisted more than 2000 people," he said, with mattresses, soup and blankets given to families housed in community centres. Police were also looking for two people who ignored a ban and rowed across a flooded road in an inflatable rubber boat, local media reported.
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Quoting TropicalAnalystwx13:
Just wanted to get an opinion out of you guys first. Would y'all view my daily Graphical Tropical Weather Outlook if I started making one? It would in no way be affiliated with the National Hurricane Center or any other government organization and would highlight my thoughts on a particular disturbance.


That's a neat idea. I would view it.
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Quoting SFLWeatherman:
Big rain in SE FL now


Wait till tomorrow.
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Quoting Grothar:


That doesn't necessarily mean TS's. A lot of times a string of lows can form above a strong high pressure system. Not unusual this time of year. They don't reflect very low pressures on them.

That's 'cause they're in a high pressure environment, Gro. You should know that. ;-)
Member Since: July 6, 2010 Posts: 113 Comments: 32721
Looks like S Japan is going to receive more Water....


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2325. Grothar
Quoting wxchaser97:
This is the latest GFS, enjoy:)
Multiple TS popssible at once from one front!


That doesn't necessarily mean TS's. A lot of times a string of lows can form above a strong high pressure system. Not unusual this time of year. They don't reflect very low pressures on them.
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Quoting TropicalAnalystwx13:
Just wanted to get an opinion out of you guys first. Would y'all view my daily Graphical Tropical Weather Outlook if I started making one? It would in no way be affiliated with the National Hurricane Center or any other government organization and would highlight my thoughts on a particular disturbance.

Yes I would, I think it would be great to get a graphical opinion and something that is different from the NHC.
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2323. cynyc2
I don't post much, but I have to tell you about this storm.

I live in the Tucson Arizona area, and our annual rainfall rate is around 11 to 12 inches.

We just had a storm form over us that dumped 2 inches (cheap Weather Channel rain gauge) in about an hour and change. I have lived here for 18 years, and have never seen it rain like this! It is about time that this monsoon season brought us something. Hopefully Fabio will bring us more.

Back to lurker mode,

Out!
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2322. Grothar
Quoting bappit:

UUUL



OOOOOK.
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Quoting TropicalAnalystwx13:
Just wanted to get an opinion out of you guys first. Would y'all view my daily Graphical Tropical Weather Outlook if I started making one? It would in no way be affiliated with the National Hurricane Center or any other government organization and would highlight my thoughts on a particular disturbance.

Here's an example.


I would. Lots of WUers see spins before they even start spinning, and as a drought resident I'm always looking for a swirl. Swirls pan out, more often than not :)
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Quoting Neapolitan:
Don't forget the hugely abnormal three-day rainfall in Japan (up to 3.5" per hour) that has led to dozens of deaths and the evacuation of hundreds of thousands of residents. And speaking of the ice melting as though it's in a microwave: this past Wednesday, the recorded temperature at the Summit Camp weather station in Greenland reached 36 degrees. That may not sound like much, but that station sits smack in the middle of Greenland's ice cap at an altitude of 10,500 feet.

Amazing that this kind of information is not "D" Noticed!
If they are 4 degrees above freezing in Greenland at 10,500 feet, the end of ice as we know it must be nigh!
By the way we have only had about 8 days rain here in the last year! A mere 43/C on the coast today.
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Quoting Grothar:


No,I haven't. Which one?
This is the latest GFS, enjoy:)
Multiple TS popssible at once from one front!
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Quoting washingtonian115:
All of them so far today.


The blog has been wacky many times today.
Member Since: April 29, 2009 Posts: 75 Comments: 14781
2317. Grothar
Quoting redwagon:

Which nice spin? I see three nice spins in that image.


I implied all three of them. Just too tired to write, nice spin on all three.
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Wow the blog is all messed up today.
Member Since: July 6, 2010 Posts: 113 Comments: 32721
Quoting Grothar:


No,I haven't. Which one?
All of them so far today.
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If anyone can see this, I have not seen mine or anyone else's comments for the past 10 minutesish.
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Quoting CaicosRetiredSailor:
Water supplies pass tipping point

...
Even though there’s been little talk of drought in San Diego in recent months, runoff into the Colorado’s Lake Powell this year is about 46 percent of average — the third lowest since 1963. Deliveries to cities and farms aren’t immediately threatened because abundant snow two winters ago provided a respite from dry conditions that have dominated the basin since 1999.

But on every inhabited continent, clean water is getting harder to find and threats to civilization grow more stark as the global population zooms past 7 billion. The combination is having physical repercussions, such as shrinking seas, dying rivers and sinking land. They are reminders that money and ingenuity can’t defy the laws of nature forever.

I apologise for having pulse your statement and hit the minus rather than the plus.
I could not agree more with your comment but some areas are suffering extreme rains, northern Europe, Japan, and the area of northern Florida a few weeks ago to mention a few!
The general imbalance of traditional climatic conditions will no doubt continue and intensify in the coming years if not reported to the many it will be known by the few.
Planetry climatic adjustment will become a reason rather than an excuse for whats going on soon, as more unavoidable evidence emerges.
Sorry again for hitting the wrong symbol.
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Quoting TropicalAnalystwx13:
Just wanted to get an opinion out of you guys first. Would y'all view my daily Graphical Tropical Weather Outlook if I started making one? It would in no way be affiliated with the National Hurricane Center or any other government organization and would highlight my thoughts on a particular disturbance.

Here's an example.



I like it a lot. Go for it.
Member Since: April 29, 2009 Posts: 75 Comments: 14781
2311. Grothar
Quoting washingtonian115:
Holler Gro.Did you see the GFS crazy model run.


No,I haven't. Which one?
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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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