Hurricane season begins today; normal June activity expected

By: Dr. Jeff Masters , 1:38 PM GMT on June 01, 2009

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Hurricane season is upon us, and it's time to take a look at the prevailing conditions and 2-week forecast for tropical cyclone activity in the Atlantic. June is typically the quietest month of the Atlantic hurricane season. On average, we see only one named storm every two years in June. Only one major hurricane has made landfall in June--Category 4 Hurricane Audrey of 1957, which struck the Texas/Louisiana border area on June 27 of that year, killing 550. The highest number of named storms for the month is three, which occurred in 1936 and 1968. In the fourteen years since the current active hurricane period began in 1995, there have been eleven June named storms (if we include last year's Tropical Storm Arthur, which really formed on May 31). Five tropical storms have formed in the first half of June in that 14-year period, giving a historical 36% chance of a first-half-of-June named storm.


Figure 1. Tracks of all June tropical storms and hurricanes, 1851 - 2007.

Sea Surface Temperatures
Sea Surface Temperatures (SSTs) are close to average over the tropical Atlantic between Africa and Central America this year (Figure 2). These temperatures are some of the coolest we've seen since 1995, when the current active hurricane period began. This year's cool SSTs should prevent a repeat of the unforgettable Hurricane Season of 2005, which had the highest SSTs on record in the tropical Atlantic. Note also that SSTs along the Equatorial Pacific off the coast of South America are quite a bit above average, signaling the possible start of an El Niño episode. As I discussed in Friday's post, odds are increasing for a weak El Niño to form in time for hurricane season, and this should cut down on the number and intensity of Atlantic tropical storms and hurricanes this year. However, if an El Niño is developing, it shouldn't start affecting Atlantic hurricane activity until August.

Typically, June storms only form over the Gulf of Mexico, Western Caribbean, and Gulf Stream waters just offshore Florida, where water temperatures are warmest. SSTs are 26 - 28°C in these regions, which is about 0.5°C above average for this time of year. June storms typically 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. African tropical waves, which serve as the instigators of about 85% of all major hurricanes, are usually too far south in June to trigger tropical storm formation. Every so often, a tropical wave coming off the coast of Africa moves far enough north to act as a seed for a June tropical storm. This was the case for Arthur of 2008 (which also had major help from the spinning remnants of the Eastern Pacific's Tropical Storm Alma). Another way to get Atlantic June storms is for a disturbed weather area in the Eastern Pacific Intertropical Convergence Zone (ITCZ) to push north into the Western Caribbean and spawn a storm there. This was the case for Tropical Storm Alberto of 2006 (which may have also had help from an African wave). SSTs are too cold in June to allow storms to develop between the coast of Africa and the Lesser Antilles Islands--there has only been once such development in the historical record--Ana of 1979, which coincidentally will be the name given to this year's first storm.


Figure 2. Sea Surface Temperature (SST) departure from average for June 1, 2009. SSTs were near average over the tropical Atlantic. Note the large region of above average SSTs along the Equatorial Pacific off the coast of South America, signaling the possible start of an El Niño episode. Image credit: NOAA/NESDIS.

Tropical Cyclone Heat Potential
It's not just the SSTs that are important for hurricanes, it's also the total amount of heat in the ocean to a depth of about 150 meters. Hurricanes stir up water from down deep due to their high winds, so a shallow layer of warm water isn't as beneficial to a hurricane as a deep one. The Tropical Cyclone Heat Potential (TCHP, Figure 3) is a measure of this total heat content. A high TCHP over 80 is very beneficial to rapid intensification. As we can see, the heat energy available in the tropical Atlantic has declined considerably since 2005, when the highest SSTs ever measured in the tropical Atlantic occurred. TCHP this year is similar to last year's levels, which were high enough to support five major hurricanes.


Figure 3. Tropical Cyclone Heat Potential (TCHP) for May 31 2005 (top), May 31 of last year (middle) and May 30 2009 (bottom). TCHP is a measure of the total heat energy available in the ocean. Record high values of TCHP were observed in 2005. TCHP this year is much lower, and similar to last year. Image credit: NOAA/AOML.

Wind shear
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's band of strong high-altitude winds is the main source of wind shear in June over the Atlantic hurricane breeding grounds, since the jet is very active and located quite far south this time of year.

The jet stream over the past few weeks has been locked into a pattern where a southern branch (the subtropical jet stream) brings high wind shear over the Caribbean, and a northern branch (the polar jet stream) brings high wind shear offshore of New England. This leaves a "hole" of low shear between the two branches off the coast of North Carolina, which is where Tropical Depression One formed. The low shear "hole" has dipped down into the northern Gulf of Mexico a few times. Disturbance 90L, which almost developed into a tropical storm before it came ashore in Mississippi/Alabama on May 23, took advantage of one of these low-shear areas.

The jet stream is forecast to maintain this two-branch pattern over the coming ten days. This means that the waters offshore of the Carolinas are the most likely place for a tropical storm to form during this period, though the northern Gulf of Mexico will at times have shear low enough to allow tropical storm formation. The latest 16-day forecast by the GFS model (Figure 4) predicts that the subtropical jet will weaken and retreat northwards by the middle of June, creating low-shear conditions over the Caribbean. This is a typical occurrence for mid-June, and we need to start watching the Western Caribbean for tropical storm formation by the middle of the month.


Figure 4. Wind shear forecast from the 00Z GMT June 1, 2009 run of the GFS model for June 1 (left panel) and June 17 (right panel). Currently, the polar jet stream is bringing high wind shear to the waters offshore New England, and the subtropical jet is bringing high wind shear to the Caribbean. This leaves the waters off the coast of North Carolina under low shear, making this area the most favored region for tropical storm formation over the next 7 - 10 days. By June 17, the subtropical jet is expected to weaken and move northwards, leaving the Caribbean under low shear, and favoring that region for tropical storm formation. Wind speeds are given in m/s; multiply by two to get a rough conversion to knots. Thus, the red regions of low shear range from 0 - 16 knots.

Dry air and African dust
It's too early to concern ourselves with dry air and dust coming off the coast of Africa, since these dust outbreaks don't make it all the way to the June tropical cyclone breeding grounds in the Western Caribbean and the Gulf of Mexico. Developing storms do have to contend with dry air from Canada moving off the U.S. coast; this was a key reason why 2007's Subtropical Storm Andrea never became a tropical storm. Dr. Amato Evan of the University of Wisconsin will issue his dust forecast for the coming hurricane season later this week, and I'll be discussing his forecast in an upcoming post.

Steering currents
The steering current pattern over the past few weeks has been typical for June, with 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. At present, it appears that the coming two weeks will maintain the typical June pattern, bringing many troughs of low pressure off the East Coast capable of recurving any June storms that might form. 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 2006 steering current pattern that recurved every storm out to sea--or the unfavorable 2008 pattern, that steered Ike and Gustav into the Gulf of Mexico.

Summary
Recent history suggests a 36% chance of a named storm occurring in the first half of June. The current conditions in the atmosphere and ocean are near average, so expect about a 1/3 chance of a named storm between now and June 15. The computer models are currently not forecasting development of any tropical storms over the next seven days.

I'll have an update Tuesday afternoon, when I'll discuss the Colorado State University June Atlantic Hurricane season forecast by Dr. Phil Klotzbach and Dr. Bill Gray, which will be issued Tuesday morning.

My next analysis and 2-week outlook for hurricane season is scheduled for June 13.

Jeff Masters

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Thanks Dr. Masters!!

Quoting MNTornado:
Please excuse my ignorance, but what the heck am I supposed to get out of this mess? It looks like somebody had a food war with the spaghetti!



LOL....yeah it does look like it. What you're supposed to get out of it is that the spagetti was only thrown at one part of the map, the Caribbean, GOM, and off the Southeast US coast. Notice how only one storm in June in 150 years has formed out in the middle of the Atlantic. The point is most early storms form close to home and not from African tropical waves.
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anything that could develop soon guys?
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Please excuse my ignorance, but what the heck am I supposed to get out of this mess? It looks like somebody had a food war with the spaghetti!

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Quoting lakeEFX:

LOL! my youngest daughter is named Grace, and if hurricane Grace is anything like the Grace that I know, you better get the heck outta her way!


UH OH!!!! don't tell me that...lol!

Oh and Claudette just sounds like its going to be a booger...haha
Member Since: August 30, 2007 Posts: 0 Comments: 1837
Quoting SomeRandomTexan:
At least we will get off the hook with hurricane Grace... with a name like that surely it couldn't be to destructive...lol!

LOL! my youngest daughter is named Grace, and if hurricane Grace is anything like the Grace that I know, you better get the heck outta her way!
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Another dud in the EPAC- Link
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Quoting albert0826:
i want to see some action.




..."Were so Sorry,..Uncle Albert,..but we havent seen a bloody thing all day".

Were so Sorry,..Uncle Albert



Member Since: July 3, 2005 Posts: 421 Comments: 127664
Good Day everyone! Just stopping in to say hi, being it is the start of a season most of us on the Gulf Coast dread! I'll keep watching what you all say, back to lurking!
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Quoting jeffs713:
456, that is well defined, but it also seems pretty far south. Is the latitude line just to the south of the feature the equator?


Well define for a tropical wave not for development purposes.

Yea the line just to the south is the equator. the ITCZ remains further south than normal due to the pressure forces by the subtropical ridge. It should begin to move slowly north as June progressess.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
i want to see some action.
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WAVETRAK - Northern Atlantic Sector


Current Winds
Member Since: July 3, 2005 Posts: 421 Comments: 127664
456, that is well defined, but it also seems pretty far south. Is the latitude line just to the south of the feature the equator?
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FLIGHTAWARE BREAKING NEWS

Air France Flight #447 (AFR447) was reported missing off the Brazillian coast on Monday morning.



The Airbus A330 (registration F-GZCP) with 228 people on board was an hour into the 5700 mile flight from Rio de Janeiro (GIG/SBGL) to Paris (CDG/LFPG) when contact was lost with air traffic controllers. It is presumed to have crashed in the water.

The Airbus A330 is a wide-body, twin-engine aircraft. It can seat up to 335 passengers depending on model and configuration. The Air France A330-200 (332) configuration seats 40 in Affaires (business) Class and 179 in Tempo (economy) Class. The aircraft has a range of nearly 6,750 nautical miles. Airlines can choose between GE, Pratt & Whitney, or Rolls Royce engines for the aircraft. Air France equips their A330s with GE engines.

CNN is reporting that the crew reported electrical problems prior to disappearing.

This flight occured entirely outside the FlightAware service area, so no flight plan, radar, or other flight tracking data is available.

Developing. . .

FlightAware PhotoPhoto Courtesy of FlightAware.com


Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting Kahlest:


Link

That is the link to the story, sounds like they really don't have a clue what happened other than the plane is most likely down as it would have run out of fuel by now and they have been getting repeated signals from the flight recorders.
A real tragedy but on a weather related note, if the plane was actually crusing at 35,000 feet, and with working on-board weather information for the route to avoid inclement weather, I do not see how lightening could have brought this plane down......We may never know unless wreakage or the black boxes are located and retreived but it was a quick catastropic wing/plane failure of some kind such as a complete "fly by wire" electrical failure, huge turbulence pocket, mid-air collision with something or, an on-board explosion IMHO.
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Quoting Kahlest:


Link

That is the link to the story, sounds like they really don't have a clue what happened other than the plane is most likely down as it would have run out of fuel by now and they have been getting repeated signals from the flight recorders.

Air France jet missing after hitting Atlantic stormLink
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You can barely see a Caribbean storm with the 12Z run. Still some spin though. Link
She might have a friend in the EPAC too.
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From lowercal's blog..The 747 and Piggyback Shuttle Atlantis live Flight tracker.



07:55AM PDT 08:03AM PDT
Arrival 10:52AM MDT 11:13AM MDT
Speed 340 kts 327 kts
Altitude 15000 feet 15200 feet


Boeing 747-200 (quad-jet) (B747/G)
Origin Edwards Afb (KEDW - track or info)
Destination Biggs Aaf (Fort Bliss) (KBIF - track or info)
Other flights between these airports
Route HEC PKE PXR IWA SSO (Decode)
Date Monday, Jun 01, 2009
Duration 2 hours 10 minutes

Member Since: July 3, 2005 Posts: 421 Comments: 127664
Fast upper winds around the crest of a ridge in the EPAC helping to generate showers BOC

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Vortex95:
Where there any severe storms in south miami about an hour ago I see nothing of it now.?


I live in Homestead, and we have just had a little rain and thunder. Nothing major. I can see the sun through the clouds now.
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TRMM revealed the damage done by both 90L and 91L, the frontal low pressure and the bands of 90L. Abover average rainfall for May across the entire Greater Antilles, that is, Hispaniola, Jamaica, and Cuba; along with the Turks and Caicos, The Bahamas and Floirda.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
I am guessing Dr. Masters looked at the EURO run this morning and found low pressure in the Western Carribean 240 hours from now.. so the GFS is not the only one in the game, it'll be an interesting month.
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85 GHz Radiance show a well define tropical wave in the Central Atlantic



Member Since: July 24, 2005 Posts: 407 Comments: 19076
69. auburn (Mod)
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**Transponders NOT flight recorders
Member Since: August 27, 2008 Posts: 0 Comments: 29
At least we will get off the hook with hurricane Grace... with a name like that surely it couldn't be to destructive...lol!
Member Since: August 30, 2007 Posts: 0 Comments: 1837
Quoting stillwaiting:
looks like the air france flight might have gone down in some storms in the ITCZ,imo


Link

That is the link to the story, sounds like they really don't have a clue what happened other than the plane is most likely down as it would have run out of fuel by now and they have been getting repeated signals from the flight recorders.
Member Since: August 27, 2008 Posts: 0 Comments: 29
Quoting JRRP:
the most active wave of the season near lesser antilles


ive seen more "90L"
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Blogs probably going to have a few more people in now since the season has officially kicked off...

BTW Doc very well done and good read!
Member Since: August 30, 2007 Posts: 0 Comments: 1837
Big Worry' for hurricane season
Disturbing new phenomenon could change the way we understand the storms.
with close to home pop up storms that leave little time for warnings
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Good Morning everyone, great read Doc!
Member Since: August 25, 2006 Posts: 1 Comments: 3016
Good morning everyone
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Thank you for this update, Dr. Masters.

I'm rockhounding on the 13th [petrified wood and fossils] so I hope things hold off in the tropics for some time to come! :)
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Thanks, Doc.
A great two-week outlook imho
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nice update doc now we sit and wait watch see
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Morning All......Great Blog Dr. M, covering all of the major "fluid" factors which must come together for major storm activity and June is not the time/place to look with the exception of a few anomolies that you have noted.......I missed the issue of the jet stream positions over the last few weeks which provides a very nice explanation as to the two recent lows we experienced......Hopefully, an evolving El Nino (which I beleive Tampa Spin nicely noted in terms of anomolies about a month ago)will bring an early end to the normal destruction associated with the season..
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NEW BLOG ENTRY POSTED:
South Florida StormWatch
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Member Since: July 3, 2005 Posts: 421 Comments: 127664
Hmmm... the long range GFS is interesting. Quite a ways out, but its showing a very prominent system late next week in the carribean.
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Blog Update
Reflector site for those at work, which now also includes Weather456, daily updates


AOI #1

AOI #2
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atlantis is headed home!!!(from Edwards AFB)
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Thank you for the breakdown Dr. Masters.
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that area in the ITCZ looks like conditions maybe favorable for some development over the next 48hrs,IMO
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appreciate it guys!
Member Since: August 30, 2007 Posts: 0 Comments: 1837
Quoting SomeRandomTexan:
Levi, Scott, Weather, or anyone who wants to take a stab at it---

The BOC convection is that from upper level diffluence or is this just the old boundary from the front? Do you give this any probability of forming? I don't have any links right now since I'm at work so thanks for the answers...


This area is just being enhanced by high CAPE and Theta values in this area and the subtropical jet. I personally don't foresee any development in this area due to the shear.
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I always start off by checking the shear maps....
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Quoting IKE:


It's under 50-60 knots of shear with no vorticity.

I'd say no.


And I'd agree.
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Quoting SomeRandomTexan:
Levi, Scott, Weather, or anyone who wants to take a stab at it---

The BOC convection is that from upper level diffluence or is this just the old boundary from the front? Do you give this any probability of forming? I don't have any links right now since I'm at work so thanks for the answers...


It has NO chance to develop! Shear is off the roof top and Convection it way up in the upper levels and yes it was from the Front that extends into the Atlantic. If this hangs around for a while which it could then in about 7-10 days something could develop but, will be very slow process.
Member Since: September 2, 2007 Posts: 178 Comments: 20439

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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.