July Atlantic hurricane outlook
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
Reader Comments
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Click for loop
Well, it was meant as humor, but come on. The "AGW believers (because it's a fact)" tell us over and over what the CLIMATE is going to be like in 5 or 10 years. And the "AGW believers (because it's a fact)" will tell you over and over that climate is much, much more complicated that WEATHER. But those same ones can't predict what the WEATHER will be like next week (remember, weather is much simpler than climate). Just some thoughts that come to mind when I read the endless "proof" of AGW.
smart remarks are better than dumb remarks???
Link
If I may paraphrase Neapolitan's earlier post...
"Sigh..."
Ah he's at it again :).Hater hater alligator.
i have some 151 proof and it;s friday...
Drew Brees signs 5 yr 100 million deal
You're too young to have gone through the endless climate scares that the media and "scientists" have tried to heap upon the public throughout the years. When I was in high school, we were going to be in an ice age by now, starving to death because we wouldn't be able to grow enough food. Now (when we were supposed to all be frozen in ice) they're telling us, no, no, it's going to be too hot. We'll all be starving to death because we can't grow enough food. Remember these days when you hit your 50's and 60's. You'll have an entirely different set of life experiences to draw upon when the newest major "scare" starts coming out of the media. I'm reminded of the bird flu epidemic that should've taken most of us out by now. Or the AIDS virus that should've decimated the population. Both are definite concerns and should be treated as such. But the breathless panic that the media sensationalizes is unneeded.
fly to 29N95W and ya should get all ya want....
NATIONAL WEATHER SERVICE JACKSONVILLE FL
1022 AM EDT FRI JUL 13 2012
...THE FLOOD WARNING CONTINUES FOR THE FOLLOWING RIVERS IN FLORIDA...
SANTA FE RIVER AT FORT WHITE AFFECTING ALACHUA...BRADFORD...
COLUMBIA...GILCHRIST...SUWANNEE AND UNION COUNTIES
PRECAUTIONARY/PREPAREDNESS ACTIONS...
SAFETY MESSAGE...RESIDENTS AND THOSE WITH INTERESTS ALONG THE RIVER
SHOULD TAKE ACTION TO PROTECT THREATENED PROPERTY. HIGH AND FAST
FLOWING RIVERS ARE NOT SUITABLE FOR RECREATION OF ANY KIND. KEEP
CHILDREN AWAY FROM FLOODED AREAS. DO NOT DRIVE VEHICLES THROUGH
FLOODED AREAS. TURN AROUND...DON`T DROWN.
Dont forget the African Killer Bee Swarm that was heading here to the US..I actually saw an article the other day of the impending doom of those bees..If I listen to every sensationalized news story, I would be putting my life savings in a fortified bus to have built in my backyard 30 feet in the ground waiting on the mayan countdown..
Yep. Took me a long, long time to learn this lesson.
yawn....
I don't follow media, I follow science, but thanks for the tip!
If I'm correct (and I may entirely be incorrect because I'm too young) only a few scientists predicted an Ice Age back then because they saw a pattern of ice ages over the last hundreds of thousands of years and concluded that we might be heading into an ice age... now I don't know if this, translated to the media, was changed to "SCIENTISTS SAY AN ICE AGE IS COMING"... I don't know much about back then.
What I do know now, is if I follow the real SCIENCE, I know the earth is warming much too fast for our own good.
The bird flu epidemic, again probably exaggerated by tenfold by the media.
It's a real shame though that most people follow the media and not the science and this may be the number one reason why today so many people deny global warming...
LOL..You are one of the nicest bloggers here on this blog!!
Yea, I also find it tiring. :S
i think 43 feet is the proper depth for that event...
Me too.
Pretty boring weather this afternoon. El-nino just may keep this years hurricane season in check.
The only flies in the ointment are this gulf low and this upper level low east of the Bahamas. Sometimes these upper lows can burrow down to the surface. Either way it looks like a rain maker for FL come Sunday and Monday.
WE DAT
ATLANTA FOREVER
no development ;)
CURRENT ESTIMATE
Date (yyyymmddhh): 2012071311
SATCON (2mem): MSLP = 980 hPa MSW = 72 kt
ADT: 984 hPa 72 kt Scene: UNFRM
CIMSS AMSU: 980 hPa 72 kt Bias Corr: 0 (MW)
CIRA AMSU: NA hPa NA kt Tmax: NA
CIMSS/NESDIS-USAF/NRL AMSU TC Intensity Estimation:
TROPICAL STORM FABIO
Friday 13jul12 Time: 1142 UTC
Latitude: 15.02 Longitude: -110.29
Storm position corresponds to AMSU-A FOV 28 [130]
-------------------------------------------------- ---------------
| Estimated MSLP: 980 hPa
| Estimated Maximum Sustained Wind: 72 kts
| Estimate Confidence: Fair ( /- 10mb /- 12kts )
-------------------------------------------------- ---------------
ZZZZZZZZZZZZZZZZZzzzzzzzzzzzzzzzzz.
well its in purple for some type of formation..it has a huge spin and my NWS actually spoke about it
We be trollin!
purple is just showing up from rotation, typical TCFP.
And the NWS mentions just about all rotations as well.
The tropical atlantic is empty
24 hours
48 hours
Empty? What is this nonsense?
Sharman, the park ecologist, echoed that sentiment, saying he's heard from experts that "they would not be surprised" to see more such landslides inside the national park if temperatures continue to warm.
"Certainly we are seeing an increase in large landslides over the past decades," Geertsema said, citing his 2006 study that found between 1973 and 2003 the average in northern British Columbia increased from 1.3 large landslides per year to 2.3.
Moreover, he said, most of the slides in northern British Columbia are happening in the warmest years.
Just adding another dimension to the issues.......
Scientific Facts.
Let the Denialists say what they want ;)
jk, but its empty, sorry to dash anyone's hopes
Remnant Daniel, TS Imilia, and TS Fabio......
I think he's bored and is just trying to stir up trouble.
In August 2011, the pond looked like this:
Now in July 2012:
We missed the deluge that hit south of here but lucked out with about 4 inches of slow rain over the last few days.
Hard to stay dry in SE Texas today...but hope everyone stays safe.
At least its been cooler than the upper 90s we had, but it is humid and warm enough to feel like you will grow mold in your lungs from staying outside...
trouble?
bored?
naawww.
I just speak the truth.
Im Objective, not biased to da swirls
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