July Atlantic hurricane outlook

By: Dr. Jeff Masters , 12:55 PM GMT on July 13, 2012

Share this Blog
60
+

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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 2261 - 2211

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

15/2101 UTC 23.2N 137.8E T1.5/1.5 08W -- West Pacific
Member Since: March 16, 2012 Posts: 127 Comments: 7950
Quoting WxGeekVA:


.... maybe if it stays persistent...

Who am I kidding, I'm just in depression from the lack of a storm.

Come play in the rain in Austin!

Member Since: Posts: Comments:
Member Since: March 16, 2012 Posts: 127 Comments: 7950
Quoting allancalderini:
karin???It better go to Korea and not to Japan they had serious flooding there.
Yes the remnants of Karin just wouldn't dissipate.Just like Daniel.
Member Since: August 14, 2010 Posts: 10 Comments: 17095
CI# /Pressure/ Vmax
5.6 / 958.3mb/104.6kt


Final T# Adj T# Raw T#
5.1 5.0 5.0

Member Since: March 16, 2012 Posts: 127 Comments: 7950
Quoting washingtonian115:
I brought it up first...Lol.

I told ja'll that Daniel is like the Karin of the east pacific.
karin???
Quoting MAweatherboy1:
This West Pac depression is (hopefully) going to provide some relief to a very drought stricken Korean peninsula...

It better go to Korea and not to Japan they had serious flooding there.
Member Since: Posts: Comments:
Quoting ncstorm:


500mb Vorticity Map
Good vorticity off of Florida and I see the blob near Bermuda has some as well.
Member Since: August 14, 2010 Posts: 10 Comments: 17095
Quoting washingtonian115:
I brought it up first...Lol.

I told ja'll that Daniel is like the Karin of the east pacific.
karin???
Member Since: Posts: Comments:
Quoting Chicklit:

really? isn't this their monsoon season? or end of it?

Worst drought in a century.

Link
Member Since: Posts: Comments:
Quoting MAweatherboy1:
This West Pac depression is (hopefully) going to provide some relief to a very drought stricken Korean peninsula...


really? isn't this their monsoon season? or end of it?

wow, I wasn't aware of that; here's a story link about the Korean drought:
Link Korean Drought Worst In A Century For North And South Korea


06/26/12 09:28 PM ET
Member Since: Posts: Comments:
Member Since: Posts: Comments:
This West Pac depression is (hopefully) going to provide some relief to a very drought stricken Korean peninsula...

Member Since: Posts: Comments:
Quoting JLPR2:


If it reaches the Wpacific at this state it might try to revive over there. That would be an interesting accomplishment.


That is a good point. It's all uphill temperature wise from where he is now....
Member Since: Posts: Comments:
2248. ncstorm


500mb Vorticity Map
Member Since: August 19, 2006 Posts: 13 Comments: 15689
bo-ring...maybe Dr. Masters should go on vacation.
Member Since: Posts: Comments:
Stop messing with that tropical depression it brudiful(lololololol)
Member Since: August 14, 2010 Posts: 10 Comments: 17095
2245. JLPR2
Quoting MAweatherboy1:
What kind of tropical depression is this?



To me it looks good, the long tail/ feeder band is a little weird.


Compare the intensity of that convection to Fabio's.



Ha! Poor Fabio is hitting the cold.
Member Since: Posts: Comments:
Quoting MAweatherboy1:
What kind of tropical depression is this?


The kind that shouldn't have been initiated on yet.
Member Since: July 6, 2010 Posts: 113 Comments: 32281
Quoting MAweatherboy1:
What kind of tropical depression is this?



An ugly one.
Member Since: September 3, 2011 Posts: 13 Comments: 3475
Quoting WxGeekVA:


.... maybe if it stays persistent...

Who am I kidding, I'm just in depression from the lack of a storm.
If GFS is correct could be tracking for named storms at the same time next week.
Member Since: August 14, 2010 Posts: 10 Comments: 17095
Quoting JLPR2:


And Chris was a really pretty category one.

Yeah...I almost want to shed a tear.

Member Since: July 6, 2010 Posts: 113 Comments: 32281
2240. JLPR2
Quoting Tropicsweatherpr:


Is approaching the dateline which divides the CPAC from WPAC.


If it reaches the Wpacific at this state it might try to revive over there. That would be an interesting accomplishment.
Member Since: Posts: Comments:
What kind of tropical depression is this?

Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:

Negative.

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN JUL 15 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER BLAKE


.... maybe if it stays persistent...

Who am I kidding, I'm just in depression from the lack of a storm.
Member Since: September 3, 2011 Posts: 13 Comments: 3475
Quoting beell:


Good point, allancalderini.
I brought it up first...Lol.

I told ja'll that Daniel is like the Karin of the east pacific.
Member Since: August 14, 2010 Posts: 10 Comments: 17095
Quoting JLPR2:
Ex-Daniel is looking somewhat alive.


Is approaching the dateline which divides the CPAC from WPAC.
Member Since: Posts: Comments:
2235. beell
Quoting allancalderini:
I just want to say also if bret and Cindy were born of the same front a similar situation can happen and we can have Ernesto and florence out of it.


Good point, allancalderini.
Member Since: Posts: Comments:
Quoting WxGeekVA:


The blob near Bermuda continues to look better... Maybe a 10% yellow next TWO by the NHC?

Negative.

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN JUL 15 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER BLAKE
Member Since: July 6, 2010 Posts: 113 Comments: 32281
Quoting Tazmanian:




likey the lift overe of EX Emilia


That's kind of nit-picky..... OK, EX....
Member Since: Posts: Comments:
2232. JLPR2
Ex-Daniel is looking somewhat alive.
Member Since: Posts: Comments:
Quoting WxGeekVA:


The blob near Bermuda continues to look better... Maybe a 10% yellow next TWO by the NHC?
I'm surprised they didn't have it mentioned in their discussion.
Quoting JLPR2:


And Chris was a really pretty category one.
I know.A really beautiful storm he was.Such a delight to track :).
Member Since: August 14, 2010 Posts: 10 Comments: 17095
I'm tired of seeing this!!!!!!!!




Member Since: June 20, 2012 Posts: 0 Comments: 2159
2229. JLPR2
Quoting washingtonian115:
Chris reached Cane strength..so you never know XD.


And Chris was a really pretty category one.
Member Since: Posts: Comments:


The blob near Bermuda continues to look better... Maybe a 10% yellow next TWO by the NHC?
Member Since: September 3, 2011 Posts: 13 Comments: 3475
Quoting JLPR2:


I would love to see that. I wish at least one would reach cane strength. XD
Chris reached Cane strength..so you never know XD.
Member Since: August 14, 2010 Posts: 10 Comments: 17095
Quoting PedleyCA:


OK, So, what is that at 15N/140W?




likey the lift overe of EX Emilia
Member Since: Posts: Comments:
2225. JLPR2
Quoting 7544:


and all going nowhere lol


That's the best part. :D
Member Since: Posts: Comments:
2224. JLPR2
Quoting ncstorm:


FOUR!!!..


I would love to see that. I wish at least one would reach cane strength. XD
Member Since: Posts: Comments:
Quoting Tazmanian:



Emilia is gone


OK, So, what is that at 15N/140W?
Member Since: Posts: Comments:
Quoting wxchaser97:
Where do you get that map and opthers like it?

Here.
Member Since: Posts: Comments:
2221. 7544
Quoting ncstorm:


FOUR!!!..


and all going nowhere lol
Member Since: Posts: Comments:
Gotta go for a little while.
Member Since: March 16, 2012 Posts: 127 Comments: 7950
Member Since: March 16, 2012 Posts: 127 Comments: 7950
Quoting PedleyCA:
Emilia and Fabio



Emilia is gone
Member Since: Posts: Comments:

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 486
NWS STORM PREDICTION CENTER NORMAN OK
530 PM CDT SUN JUL 15 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

NORTHERN NORTH DAKOTA

EFFECTIVE THIS SUNDAY AFTERNOON FROM 530 PM UNTIL MIDNIGHT CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 75 MILES WEST OF MINOT NORTH
DAKOTA TO 25 MILES EAST NORTHEAST OF DEVILS LAKE NORTH DAKOTA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU6).Link
Member Since: March 16, 2012 Posts: 127 Comments: 7950
Emilia and Fabio
Member Since: Posts: Comments:
I just want to say also if bret and Cindy were born of the same front a similar situation can happen and we can have Ernesto and florence out of it.
Member Since: Posts: Comments:
Quoting washingtonian115:
The "I" storms have been on a roll these past few years.Will Isaac follow that path?.
Maybe,maybe not
Member Since: Posts: Comments:
Ex-Daniel and Emilia
Member Since: Posts: Comments:
Quoting LargoFl:
Some U.S. residents may have a rare chance to see the aurora borealis, more commonly known as the northern lights, late tonight and into early Wednesday morning.

While the best viewing will be across Canada, including Edmonton and Winnipeg, the lights will be visible in parts of Alaska. The lights will also be visible in Portland, Ontario, Canada, which means they could be seen in upstate New York.

AccuWeather.com Expert Senior Meteorologist Paul Walker said it will be cloudy along the St. Lawrence River on New York's northern border, while hit-or-miss showers could occur in southern New England in the early evening.

The lights may also be seen as far south as Madison, Wis., and Lansing, Mich. Walker said that this corridor will also be partly cloudy with some hit-or-miss storms.

Anything for the Detroit metro area?
Member Since: March 16, 2012 Posts: 127 Comments: 7950
The "I" storms have been on a roll these past few years.Will Isaac follow that path?.
Member Since: August 14, 2010 Posts: 10 Comments: 17095

Viewing: 2261 - 2211

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

Top of Page

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.

Local Weather

Partly Cloudy
55 °F
Partly Cloudy