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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Quoting EricSFL:
It's sad too see so many of you concerned about a "mayan calendar", yet completely disregard the Bible. This is what the Nation under God has become.

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1359. LargoFl
Quoting EricSFL:
It's sad too see so many of you concerned about a "mayan calendar", yet completely disregard the Bible. This is what the Nation under God has become.
.religion and politics we try to keep out of here as a peace keeping measure
Member Since: August 6, 2011 Posts: 4 Comments: 39144
Quoting txjac:


I want it back ...loved the cooler weather we were having.


Yep. That was nice. Didn't take long to heat back up.
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1357. EricSFL
It's sad too see so many of you concerned about a "mayan calendar", yet completely disregard the Bible. This is what the Nation under God has become.
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1356. KEEPEROFTHEGATE (Mod)


lots of heat yet to come
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1354. txjac
Quoting AtHomeInTX:


The rain's gone...sigh



Fair

88°F

31°C

Humidity57%
Wind SpeedVrbl 3 mph
Barometer29.95 in (1014.2 mb)
Dewpoint71°F (22°C)
Visibility10.00 mi
Heat Index94°F (34°C)


I want it back ...loved the cooler weather we were having.
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CURRENT ESTIMATE
Date (yyyymmddhh): 2012071420
SATCON (2mem): MSLP = 969 hPa MSW = 94 kt
ADT: 960 hPa 105 kt Scene: EYE
CIMSS AMSU: 972 hPa 84 kt Bias Corr: 0 (TPC)
CIRA AMSU: NA hPa NA kt Tmax: NA
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This is a Category 2 hurricane.

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Quoting Tazmanian:



would you link that plzs or find other photo your going too kill any one thats uesing di up internet thats trying to come too the blog or on a vary slow laptop wish some may still be uesing even with some DSL user may find a little hard time geting too the blog
Thanks for the advice, it was lagging on my laptop too when I try to scroll down for some reason.
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1349. bappit
Quoting VAbeachhurricanes:
Can someone post the Fabio Discussion?

It was a couple blogs ago I think. Really not worth digging out. TWC featured him on their front page. Think the conclusion was that the ladies like him.
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On the blog right now...
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Quoting Neapolitan:
True, most of Canada, Mexico, and the Continental United States will be pretty toasty for the next few weeks. But on the plus side, people living within about 50 miles of the Pacific coast will be in a for a treat...

Hot

Hot


The rain's gone...sigh



Fair

88°F

31°C

Humidity57%
Wind SpeedVrbl 3 mph
Barometer29.95 in (1014.2 mb)
Dewpoint71°F (22°C)
Visibility10.00 mi
Heat Index94°F (34°C)
Member Since: Posts: Comments:
1346. 47n91w
Quoting MAweatherboy1:
So far the effects from the CME have been very weak... We haven't even reached minor geomagnetic storm levels... Current aurora forecast:



A lot of misinformation earlier on the blog, seems that so many people are getting questionable information.

Earth is currently experience minor geomagnetic storming (G1) and has been experiencing minor radiation storming (S1) since the flare occurred on Thursday. This page shows current storm levels: http://www.swpc.noaa.gov/

The CME did reach the GOES satellites this afternoon, as evident from their magnetometer data:



The solar wind drastically increased (the yellow line, fourth down) while the polarity of the magnetic fields impacting Earth went from N to S (Bz, the red line in the top chart) went from positive (N) to negative (S):



This event was not expected to be huge, but it has been a while since a CME was directed at Earth. With plenty of preparation over the last two days, electrical grid operators, airline companies, and satellite personal are fully prepared. With some luck, the geomagnetic storming will continue into the dark hours and provide some fantastic auoroas farther south than usual.

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We are now in minor geomagnetic storm conditions:

Member Since: February 11, 2012 Posts: 83 Comments: 7836
Quoting GTcooliebai:
Didn't realize this until now, but Daniel was a rather large storm at peak intensity.




would you link that plzs or find other photo your going too kill any one thats uesing di up internet thats trying to come too the blog or on a vary slow laptop wish some may still be uesing even with some DSL user may find a little hard time geting too the blog
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Didn't realize this until now, but Daniel was a rather large storm at peak intensity.

Link
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1336 GTcooliebai: Actually it looks like our old friend Daniel was just having a smoke.

Well I was wondering why NHC quit updating the ATCF report on it. May not have been pretty, but it remained as organised as anything that they've initiated an Invest on.
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Quoting pottery:

Wow!
When the boat is overheating, that's terrible.
Hot engines are bad enough !

:):))
Well, actually it wasn't overheating but the engine wasn't cooling fast enough so we went in rather than risking more damages.
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Fabio:

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Quoting HurricaneGroupie:
does the warm water make for better fishing?
It's more of balance between cooler water and warmer water. Too warm and fish will go deeper water or cooler water farther up the Gulf Stream toward the north. Too cold, and the fish will go down to Florida. North Carolina, especially the Outer Banks, is known as the best spot for fishing along the East Coast because of the balance. The Keys in Florida is another good spot because it's very balanced all year long.
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Derived from the 14July6pmGMT (NHC) ATCF data for TropicalStormEmilia:
Its vector had changed from 14.4mph(23.2km/h) West West to 17.8mph(28.7km/h) West
MaxSusWinds had held steady at 45knots(52mph)83km/h
And minimum pressure has held steady at 997millibars

For those who like to visually track TS.Emilia's path...
HPV is Hanalei,Kauai :: HNL is Honolulu,Oahu :: OGG is Kahalui,Maui :: ITO is Hilo,Hawaii

Easternmost dot on the connected line-segments is where Emilia became a TropicalStorm again
Easternmost dot on the longest line is TS.Emilia's most recent position

The longest line is a straightline projection through TS.Emilia's 2 most recent positions to its closest approach to Hawaii's coastline. (All 4 of the endpoints below are on the same blob)
14July12amGMT: TS.Emilia had been headed toward passing 353miles(568kilometres)South of Hawaii
14July6amGMT: TS.Emilia had been headed toward passing 343miles(552kilometres) South of Hawaii
14July12pmGMT: TS.Emilia had been headed toward passing 332miles(534kilometres)South of Hawaii
14July6pmGMT: TS.Emilia was heading toward passing 322miles(519kilometres) South of Hawaii
in ~3days11hours from now

Copy&paste hpv, hnl, 13.818n155.018w, 13.96n155.063w, 14.114n155.112w, ogg, 18.911n155.681w,ito, 15.3n124.2w-15.5n125.4w, 15.5n125.4w-15.5n126.7w, 15.5n126.7w-15.5n127.9w, 15.5n127.9w-15.5n129.3w, 15.5n129.3w-15.5n130.6w, 15.5n130.6w-15.5n132.2w, 15.5n130.6w-14.25n155.154w, 18.911n155.681w-14.25n155.154w into the GreatCircleMapper for more information
The previous mapping for comparison
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Actually it looks like our old friend Daniel was just having a smoke.

Link
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True, most of Canada, Mexico, and the Continental United States will be pretty toasty for the next few weeks. But on the plus side, people living within about 50 miles of the Pacific coast will be in a for a treat...

Hot

Hot
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UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 14 JUL 2012 Time : 203000 UTC
Lat : 16:08:30 N Lon : 114:58:35 W


CI# /Pressure/ Vmax
5.6 / 960.0mb/104.6kt


Final T# Adj T# Raw T#
5.6 5.5 5.5

Estimated radius of max. wind based on IR : 13 km

Center Temp : -23.6C Cloud Region Temp : -66.0C

Scene Type : EYE

Positioning Method : SPIRAL ANALYSIS

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : PACIFIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 90km
- Environmental MSLP : 1013mb

Satellite Viewing Angle : 29.8 degrees

************************************************* ***
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does the warm water make for better fishing?
Quoting Bluestorm5:
Well, that was some bad luck today... I was going offshore fishing today 20 miles east of Carolina Beach, but boat started to overheated 4 miles offshore in 2 foot waves so we had to retreat to the shore. Water is crazy warm in ocean though!
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1332. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 39144
1331. pottery
Constant drizzle here all day.
Some distant thunder earlier to the south with very dark sky.
Nice and cool though.
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http://www.sec.noaa.gov/pmap/gif/pmapN.gif
Member Since: May 21, 2007 Posts: 0 Comments: 440
1329. pottery
Quoting Bluestorm5:
Well, that was some bad luck today... I was going offshore fishing today 20 miles east of Carolina Beach, but boat started to overheated 4 miles offshore in 2 foot waves so we had to retreat to the shore. Water is crazy warm in ocean though!

Wow!
When the boat is overheating, that's terrible.
Hot engines are bad enough !

:):))
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hey MAweatherboy1.

Apparently the CME arrived at 11:00 PDT at least according to these guys. I don't get the "aurora forecast" for the Artic since they are in summer and the sun never sets. Good luck seeing any aurora.
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Quoting Bluestorm5:
In your opinion, who's the best and who's the worst?

Stewart's the best, Brown's the worst. They're generally all experts though.
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Member Since: September 18, 2010 Posts: 0 Comments: 5234
Try science before posting total garbage on this blog. In cases where ignorance isn't bliss, try and keep your ignorance to yourself.

Science

(It's a link to a NASA article on the Dark Rift, which does exist, but has no bearing whatsoever on the earth.)
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So far the effects from the CME have been very weak... We haven't even reached minor geomagnetic storm levels... Current aurora forecast:

Member Since: February 11, 2012 Posts: 83 Comments: 7836
We may have a new West Pacific storm soon...



Member Since: February 11, 2012 Posts: 83 Comments: 7836
Conversely, we will probably not see another Atlantic July like 2005 for quite some time. From Dr. M's Blog:

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.

That was an amazing, and devastating year, and the only storm I "remember" from that year was Katrina.
Member Since: August 8, 2006 Posts: 0 Comments: 9220
Is Fabio a major hurricane, lol?

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 14 JUL 2012 Time : 200000 UTC
Lat : 16:03:54 N Lon : 114:55:02 W


CI# /Pressure/ Vmax
5.6 / 960.0mb/104.6kt


Final T# Adj T# Raw T#
5.6 5.6 5.6


Estimated radius of max. wind based on IR : 12 km

Center Temp : -19.4C Cloud Region Temp : -66.4C

Scene Type : EYE

Positioning Method : SPIRAL ANALYSIS

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : PACIFIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
Member Since: February 11, 2012 Posts: 83 Comments: 7836
Quoting TropicalAnalystwx13:

I don't really trust the forecast's from Brown or Berg. They turn out to be wrong a lot. By some pretty big margins as well.
In your opinion, who's the best and who's the worst?
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Quoting VAbeachhurricanes:
Can someone post the Fabio Discussion?




go too the nhc site
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Well, that was some bad luck today... I was going offshore fishing today 20 miles east of Carolina Beach, but boat started to overheated 4 miles offshore in 2 foot waves so we had to retreat to the shore. Water is crazy warm in ocean though!
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The next area to watch is for trough split development is off the US East Coast around the 19th or so, next week.
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As noted by Dr. in his Blog from yesterday, this is a totally amazing season for the E-Pac so far this year.
Member Since: August 8, 2006 Posts: 0 Comments: 9220
Quoting MAweatherboy1:
Wow... 90mph and forecast to begin weakening immediately?

I don't really trust the forecast's from Brown or Berg. They turn out to be wrong a lot. By some pretty big margins as well.
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Quoting VAbeachhurricanes:
Can someone post the Fabio Discussion?


Post #1305
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.