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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Member Since: July 21, 2011 Posts: 83 Comments: 7167
http://www.yr.no/satellitt/afrika_animasjon.html

wave train last 30 days across Africa
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting GeorgiaStormz:


you wouldnt expect the NHC to go higher would you?

maybe its because whenever guidance says something, buoys, ships, and sometimes recon tend to show lower winds.


I might be wrong, but with Fabio, the only estimates they have as to the storm's intensity are the satellite estimates and when Dvorak is 5.5 and CI is 5.8, I would expect higher than 90 knots.
Member Since: June 26, 2012 Posts: 0 Comments: 188
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Quoting 954FtLCane:
Link
Don't work.
Member Since: August 14, 2010 Posts: 10 Comments: 16444
1855. mati
Quoting Skyepony:New model run on Fukushima's radioactive pollution in the Pacific Ocean shows greatest concentrations of C-137 won't reach West coast of USA for 10 years..


I'll be nice and dilute by then...

Of course I already have been exposed to much more radiation thanks to the American above ground nuclear tests :)

Link
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Link
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The wave off of Africa won't develop.But it is giving us a clue that once that SAL goes down we could start to see development.
Member Since: August 14, 2010 Posts: 10 Comments: 16444

Loop
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Quoting TropicalAnalystwx13:



There is turning of the clouds on both the one just emerging as the one behind. They have to remain south of 15N to avoid the thick sal.
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting wxchaser97:
Not really for middle NH.


but cool for nascar
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting GeorgiaStormz:


89F is quite cool
Not really for middle NH.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
The wave train is a rollin'.
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Quoting TropicalAnalystwx13:


Big SAL above the train = waves die if they go north
and more coming off
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Quoting Tropicsweatherpr:


Do you have a loop of that?

Member Since: July 6, 2010 Posts: 113 Comments: 31575
Quoting wxchaser97:
Should be a hot one for the NASCAR race today:
Loudon NH

This Afternoon A slight chance of showers and thunderstorms after 3pm. Partly sunny, with a high near 89. South wind 5 to 7 mph. Chance of precipitation is 20%.
Sorry if this is off topic


89F is quite cool
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Should be a hot one for the NASCAR race today:
Loudon NH

This Afternoon A slight chance of showers and thunderstorms after 3pm. Partly sunny, with a high near 89. South wind 5 to 7 mph. Chance of precipitation is 20%.
Sorry if this is off topic
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting TropicalAnalystwx13:


Do you have a loop of that?
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Member Since: July 6, 2010 Posts: 113 Comments: 31575
Quoting washingtonian115:
He hates me for some odd reason.i'm not sure why.Anybody that post insults my way he gives them a plus for it.He needs to come out from hiding.


i didnt insult you did i?
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Quoting GeorgiaStormz:


who is he that you should hate him so much?
He hates me for some odd reason.i'm not sure why.Anybody that post insults my way he gives them a plus for it.He needs to come out from hiding.

Hurrihistory it won't likely develop thanks to dry air at the moment.
Member Since: August 14, 2010 Posts: 10 Comments: 16444
The small area of convection just to the SW of the Cape Verde Islands has a very well defined circulation! This can clearly be seen by looking at the latest visible loop.
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WTPN31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/150421Z JUL 12//
AMPN/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. TROPICAL DEPRESSION 08W (EIGHT) WARNING NR 001
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
151200Z --- NEAR 22.4N 140.1E
MOVEMENT PAST SIX HOURS - 300 DEGREES AT 13 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY A COMBINATION OF
SATELLITE AND SYNOPTIC DATA
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 22.4N 140.1E
---
FORECASTS:
12 HRS, VALID AT:
160000Z --- 23.9N 137.3E
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 24 HR POSIT: 295 DEG/ 15 KTS
---
24 HRS, VALID AT:
161200Z --- 25.2N 134.3E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 36 HR POSIT: 300 DEG/ 17 KTS
---
36 HRS, VALID AT:
170000Z --- 26.9N 131.1E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 060 NM NORTHEAST QUADRANT
055 NM SOUTHEAST QUADRANT
055 NM SOUTHWEST QUADRANT
060 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 315 DEG/ 17 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
171200Z --- 29.3N 128.3E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 060 NM NORTHEAST QUADRANT
055 NM SOUTHEAST QUADRANT
055 NM SOUTHWEST QUADRANT
060 NM NORTHWEST QUADRANT
VECTOR TO 72 HR POSIT: 350 DEG/ 17 KTS
---
72 HRS, VALID AT:
181200Z --- 36.0N 126.9E
MAX SUSTAINED WINDS - 020 KT, GUSTS 030 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
---
REMARKS:
151500Z POSITION NEAR 22.8N 139.4E.
TROPICAL DEPRESSION 08W, LOCATED APPROXIMATELY 165 NM SOUTH-
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 13
KNOTS OVER THE PAST SIX HOURS. THIS WARNING SUPERSEDES AND CANCELS
REF A, JOINT TYPHOON WRNCEN PEARL HARBOR HI 150421Z JUL 12 TROPICAL
CYCLONE FORMATION ALERT (WTPN21 PGTW 150430). MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 151200Z IS 10 FEET. NEXT WARNINGS AT 152100Z,
160300Z, 160900Z AND 161500Z.//
NNNN
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Quoting washingtonian115:
I see the hater continues to plus your comments.How wonderful :).Hey dude keep doing it because your only motivating me more.I see you won't come out from hiding.


who is he that you should hate him so much?
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Good Sunday to everyone...looking at what's coming off Africa:



And some data from this latest solar flare event:

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Member Since: March 16, 2012 Posts: 127 Comments: 7928
Just a small idea of what a solar storm impact would do to us, only thing is that this is hollywood's version, so these folks wouldn't be all dressed up, shaved, women with makeup and hair all did.

Only the first 1:30 is actually credible, after that it's all hollywood crap.

You will have to copy and paste the link as it wont let me embed the code over.


http://www.youtube.com/watch?v=JwfCRAtkYEI&featur e=channel&list=UL
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Member Since: March 16, 2012 Posts: 127 Comments: 7928
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting GeorgiaStormz:


it was possible to have a weak one by now, but i didnt count on it.
I dont trust those forecasts to be on time
I see the hater continues to plus your comments.How wonderful :).Hey dude keep doing it because your only motivating me more.I see you won't come out from hiding.
Member Since: August 14, 2010 Posts: 10 Comments: 16444
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1827. Skyepony (Mod)
New model run on Fukushima's radioactive pollution in the Pacific Ocean shows greatest concentrations of C-137 won't reach West coast of USA for 10 years.. There is a good video at that link that isn't embedding well.

5 years after


10 years later


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Member Since: March 16, 2012 Posts: 127 Comments: 7928
SAL to PR, might clip FL



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Quoting washingtonian115:
Okay :).I thought El nino was suppose to be here by now?.


it was possible to have a weak one by now, but i didnt count on it.
I dont trust those forecasts to be on time
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Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting wxchaser97:


A delayed El Nino if the MJO continues in the Indian Ocean.
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Member Since: March 16, 2012 Posts: 127 Comments: 7928
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting GeorgiaStormz:


ok croweater
Okay :).I thought El nino was suppose to be here by now?.
Member Since: August 14, 2010 Posts: 10 Comments: 16444
Quoting washingtonian115:
No I won't give up.Expect development off of Africa in another eek to two weeks.The waves are looking more and more robust.


ok croweater
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Good Morning. As I mentioned last evening, statistically about 60 waves traverse the Atlantic from Africa towards the Caribbean during July/August/September and only a very small percentage actually become tropical depressions or higher. And we have seen extremely robust waves emerge of the coast and fizzle by the time they reach the Cape Verde Islands during these same time periods over the years.

The models are pretty good at honing in on which ones might develop. No one knows the time and hour when they will start developing in the Central-Atlantic but we should start seeing model consensus on possible development in the coming 3-6 week period.
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
923 AM EDT SUN JUL 15 2012

UPPER TROUGH BETWEEN THE 2 LOWS TO THE NE AND SW RESPECTIVELY MOVING
NW ACROSS THE S FLA AT THE MOMENT. UNDER MOSTLY CLOUDY SKIES...RADAR
DETECTS WIDESPREAD SHOWERS OVER THE ATLC AND THE SE GULF OE MEX WITH
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING OVER THE E
COAST ZONES. THE WIDESPREAD CONVECTIVE ACTIVITY EXPECTED TO REMAIN
OFFSHORE WITH MAINLY AFTERNOON AND EARLY EVENING ACTIVITY OVER THE
MAINLAND. NOT AN ALL DAY RAIN OUT BUT WILL KEEP POPS AS IS IN THE
CURRENT FORECAST AS ALL AREAS HAVE A LIKELY CHANCE OF SEEING SOME
RAINFALL TODAY.
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I repeat I think el Nino is taking his time.........Todays prelimar values for SOI continue to be positive for eight days consecutive

july 8 + 6.52
july9 +5.05
july 10 +6.46
july 11 +12.25
july 12 +18.22
july 13 +15.82
july 14 +8.92

And Today preliminar values July 15 +20.50

Clearly El nino is delayed for now.

Link
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1813. Skyepony (Mod)
North Pole melting live..
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Quoting GeorgiaStormz:


i see u wont give up...2nd week of august i tell you.

That 1014 subtropical low wont be another chris.
No I won't give up.Expect development off of Africa in another eek to two weeks.The waves are looking more and more robust.
Member Since: August 14, 2010 Posts: 10 Comments: 16444
Quoting TXCaneCrasher:


I agree, not only by the totals we have dumped out but even their updates on their homepage have different totals different days. Maybe I am looking at it wrong but they should check it out. Thanks for letting me know about that page. Are you in the Houston area?
Nope, SE MI, Detroit area
Member Since: March 16, 2012 Posts: 127 Comments: 7928

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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.