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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In answer to your queriy!
"Would someone please tell us why it won’t stop raining?As the Met Office forecasts yet more downpours, what’s behind the bad weather, asks Michael Hanlon."
For every degree that the average atmospheric temps rise by 1 degree then 4% more water can be carried by the atmosphere.
Its going to rain on and off for a long time! Sorry if it upsets anybody's plans but that's just global warming for you!
...on a crash course into south america
If I told you I like mountain dew, it would be no different.?
You people don't miss anything, do you?
That might be different.
Well, we look forward to more rain then.
I better enjoy the next 2 days of relative dry.
Today was nice and hot & Breezy.
Gee, I don't know. I guess we'll have to wait for the experts.
You predicted Fabio's northward turn first. You're the expert.
And I'm not sayin'
Just saying'
:):))
Isn't that true of pretty much all soda? Everything in moderation.
:) How you doing pott? Just a'lurkin?
I agree on that. It would be good to start to see some analysis by those who have more knowledge on identifying which wave has the best signature to have the chance to develop. That is why I said earlier that I would like to see Levi and someone who has been missed for a long time Weather456 to do that.
You shut your dirty mouth! :-)
I drink it two or three times as well. Two or three times a day..
Now lets be sensible about this one? Wash, as a lot of readers will pounce if we get this one wrong:-
The scenario is set for a big hoolie over the south Atlantic arc! for want of a better word?
If something really narsty comes out of the the armpit of Africa and I am sure it will even though you might call it he Gulf of Guinea.
Temps are high in the water, shear is low in the air and nothing is going to get in the way of a big depression coming in from the East. Target, the lower Caribbean.
Just a thought at this point of course.
Wait until his metabolism slows a bit.
That's why I never worry about what the Mayan calendar. The set is incomplete. I always figured the one that predicted the position of Venus in 2025 was one that got burned.
Generally speaking. However, not necessarily. Genetics can be an amazing thing.
i work with a guy that drinks 4-5 cans of Dew a day. his teeth are just fine.
Given the access to energy and moisture Fabio has, if he did hang a sharp right into landmass it would certainly change any wx forecasts from NV to LA, at least, especially if he intensified to 3 or higher.
I'm curious why the models instantly predicted Daniel and Emilia going XTRP, but re-curving Fabio out of the gate.
I bet its no different to you drinking so much DR pepper.
I do like Dr Pepper though.
EP, 06, 2012071400, , BEST, 0, 156N, 1119W, 75, 982, HU
Link
Shortwave trough over the Pacific Northwest that wasn't there otherwise for Daniel and Emilia.
14/0000 UTC 15.5N 127.9W T2.0/3.0 EMILIA -- East Pacific
14/0000 UTC 15.7N 111.9W T4.0/4.0 FABIO -- East Pacific
EP, 06, 2012071400, , BEST, 0, 156N, 1119W, 75, 982, HU, 64, NEQ, 20, 20, 0, 0, 1010, 200, 20, 0, 0, E, 0, , 0, 0, FABIO, D,EP, 05, 2012071400, , BEST, 0, 155N, 1279W, 45, 998, TS, 34, NEQ, 50, 30, 20, 50, 1007, 150, 20, 0, 0, E, 0, , 0, 0, EMILIA, M,
First off, you might want to take a look at the map BobWallace posted at comment 498 and read the legend.
Second, I do not deny the globe is warming. In fact, I have posted on these blogs I believe it is. I have stated on this forum more than one time I have seen with my own eyes glaciers in SE and Southcentral Alaska shrink over 35-40 years time. I have also made statements more than once about my "green" lifestyle and my displeasure that "green" has become a highly-charged, politicized word.
The article I responded to was put out by msnbc who used a scientist who'd make a statement that suited their sensationalistic headline. Even at that, the scientist's words were iffy and did not say for certain what had caused this landslide near Glacier Bay.
SE Alaska's climate is similar to that of the PacNW. It is a protected seacoast and milder than central Alaska. Even southcentral Alaska (e.g. Anchorage, Kenai, Homer) has little permafrost. Again, you might want to refer to the map at 498. I know Alaska. Anyone... and rhetorical... When was the last time you saw Glacier Bay? Have you observed Mendenhall Glacier over the years since 1970? Ditto for Portage Glacier. When was the last time you walked in Summer on true tundra covered with miniature wildflowers or watched Eskimo kids play chicken on ice floes at Spring breakup in the Bering Sea?
There are many factors involved in what is going on right now with worldwide climate. Some seem to be in such a panic over it, they fail to see the whole picture. Talk about that dung pile.
Label me anything you want. None of you, not one blogger at this site, knows what I believe about AGW. Some may have assumed they do, but they don't.
I have been paid to write - but not on internet forums. Weather Underground is the only place I post. And now that I have wasted yet another of Barefootontherocks' final ration of comments, I shall...
*POOF*
You should keep that present avatar you have posted.
It suits you!
Big smile and hands out for Allies!
cause there is no caffiene.
The End
average US drinks 53 gallons of Soda a year.
And it is killing us
I drink less than 1 gallon of soda a year, in fact ive had one soda, a sierra mist, so far in july
I don't drink a lot of Dr. Pepper. Literally 95% of what I drink is water. The rest is milk or fruit juice.
65% water
15%Gatorade
15%Fruit Juice
4% protien shakes
1% Soda(sprite fanta sierra mist) or something like Hi-C
You actually feel healthier if you don't drink soda.
I'm actually not sure about that. Ioke didn't lose his.
Talk about a generalized sensationalist comment!
For me milk can= death due to my very severe dairy allergy. I really sucks because I can't eat/drink a lot of stuff other people can have coupled with my bad nut allergy. Fabio is a 85mph storm at 11pm EDT.Link
Luckily I don't have that problem. However, I work in the dairy (Walmart) so much to the point where I'm literally sick of milk.
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