NOAA predicts a near-normal Atlantic hurricane season

By: Dr. Jeff Masters , 9:17 PM GMT on May 24, 2012

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NOAA forecasts a near-normal Atlantic hurricane season in 2012, in their May 24 outlook. They give a 50% chance of a near-normal season, a 25% chance of an above-normal season, and a 25% chance of a below-normal season. They predict a 70% chance that there will be 9 - 15 named storms, 4 - 8 hurricanes, and 1 - 3 major hurricanes, with an Accumulated Cyclone Energy (ACE) 65% - 140% of the median. If we take the midpoint of these numbers, NOAA is calling for 12 named storms, 6 hurricanes, 2 major hurricanes, and an ACE index 102% of normal. This is very close to the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2011 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 153% of the median. Only five seasons since 1995 have not been above normal--including four El Niño years (1997, 2002, 2006, and 2009), and the neutral 2007 season.


Figure 1. The strongest Atlantic hurricane of 2011, Ophelia, as seen at 1:40 pm EDT October 1, 2011. At the time, Ophelia was a Category 3 hurricane with 120 mph winds. At 11 pm that night, Ophelia peaked at Category 4 strength with 140 mph winds. Image credit: NASA.

The forecasters cited the following main factors that will influence the coming season:

1) Near-average sea surface temperatures (SSTs) are expected in the hurricane Main Development Region (MDR), from the Caribbean to the coast of Africa between between 10°N and 20°N. SSTs in the MDR during April were near-average, and are expected to remain so during hurricane season, based on current observations, climatology, and long-range model forecasts.

2) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO): "During 1995-2010, some key aspects of the tropical multi-decadal signal within the MDR have included reduced vertical wind shear and weaker easterly trade winds, below-average sea-level pressure, a configuration of the African easterly jet that is more conducive to hurricane development from tropical cloud systems (aka Easterly waves) moving off the African coast, and warmer than average SSTs."

3) An El Niño event may occur this year: "Another climate factor known to significantly impact Atlantic hurricane activity is the El Niño-Southern Oscillation (ENSO.) The three phases of ENSO are El Niño, La Niña, and ENSO-Neutral. El Niño events tend to suppress Atlantic hurricane activity, while La Niña events tend to enhance it (Gray 1984). If El Niño fails to develop, the probability of an above-normal Atlantic hurricane season will be higher and the actual seasonal activity will likely be toward the upper end of our predicted ranges." There is currently of lot of uncertainty whether or not an El Niño event will develop in time for the August - September - October peak of hurricane season--the latest NOAA El Niño discussion is giving a 41% chance of an El Niño event during hurricane season, and a 48% chance of neutral conditions.

4) NOAA is increasingly using output from ultra-long range runs of the computer forecast models we rely on to make day-to-day weather forecasts, for their seasonal hurricane forecasts: "The outlook also takes into account dynamical model predictions from the NOAA Climate Forecast System (CFS), the European Centre for Medium Range Weather Forecasting (ECMWF), the United Kingdom Meteorology (UKMET) office, and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble. These models show large spreads in the ENSO forecasts for ASO, ranging from ENSO-Neutral to a moderate-strength El Niño episode. As a result, their forecasts for the Atlantic hurricane season also show a considerable spread, ranging from slightly above normal to slightly below normal."

How accurate are the NOAA seasonal hurricane forecasts?
A talk presented by NHC's Eric Blake at the 2010 29th Annual AMS Conference on Hurricanes and Tropical Meteorology studied the accuracy of NOAA's late May seasonal Atlantic hurricane forecasts, using the mid-point of the range given for the number of named storms, hurricanes, intense hurricanes, and ACE index. Over the past twelve years, a forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Using another way to measure skill, the Mean Squared Error, May NOAA forecasts for named storms, hurricanes, and intense hurricanes had a skill of between 5% and 21% over a climatology forecast. Not surprisingly, NOAA's August forecasts were much better than the May forecasts, and did significantly better than a climatology forecast.


Figure 2. Mean absolute error for the May and August NOAA seasonal hurricane forecasts (1999 - 2009 for May, 1998 - 2009 for August), and for forecasts made using climatology from the past five years. A forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

I'll have an update on Hurricane Bud and Invest 94L Friday morning.

Jeff Masters

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Quoting CosmicEvents:
Yes.....it's a pretty definitive shot. The east/west winds(with convection developing) show up very nice. Rarely do we get LB doppler radar on a AOI at this point of cyclogenesis. It's just past Biscayne Bay passing the Dade/Broward border at the moment.



incredible this year. i want to watch them from afar and not up close and personal though. Im not a get in a storms face type of person but i respect those who are
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Never seen such uncertainty from the NHC before, especially with a strong landfalling storm like this.



Especially since right now it is supposed to make landfall and reemerge, which will cause absolutely awful flooding.
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Quoting K8eCane:



Are you sure thats the main one?
Yes.....it's a pretty definitive shot. The east/west winds(with convection developing) show up very nice. Rarely do we get LB doppler radar on a AOI at this point of cyclogenesis. It's just past Biscayne Bay passing the Dade/Broward border at the moment.
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Any rain by you yet LargoFL? Apparently the one cell that was over the Howard Frankland Bridge split into two cells. Still under a Severe T'Storm Warning.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
ALERT 1 - Severe Thunderstorm Warning

A SEVERE THUNDERSTORM WARNING IS IN EFFECT UNTIL 7:30PM EDT THURSDAY, MAY 24

Event Start: In Progress

Event End: Thursday, May 24, 2012 7:30 PM EDT
Back to Summary
HILLSBOROUGH FL-PINELLAS FL- 717 PM EDT THU MAY 24 2012 A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT
UNTIL 7:30PM EDT
Severe Weather Statement
National Weather Service Tampa Bay Area - Ruskin FL
717 PM EDT Thu May 24 2012

Hillsborough FL-Pinellas FL-
717 PM EDT Thu May 24 2012

...A Severe Thunderstorm Warning Remains In Effect Until 730 PM Edt
For Pinellas And Northwestern Hillsborough Counties...

At 717 PM EDT...Doppler Radar Continued To Indicate A Line Of Severe
Thunderstorms Capable Of Producing Quarter Size Hail...And Damaging
Winds In Excess Of 60 Mph. These Storms Were Located Along A Line
Extending From South Pasadena To Safety Harbor...Or Along A Line
Extending From Saint Petersburg To 8 Miles West Of Tampa
International Airport...Moving Northwest At 10 Mph.

Severe Thunderstorms Will Affect Portions Of...
Lealman.
South Pasadena.
Oldsmar.
Treasure Island.

Precautionary/Preparedness Actions...

In Addition To Large Hail And Damaging Winds...Continuous Lightning
Is Occurring With This Storm. Move Indoors Immediately. Lightning Is
One Of Natures Number One Killers. Remember...If You Can Hear
Thunder...You Are Close Enough To Be Struck By Lightning.
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Quoting ncstorm:


Yep!!


Well Awesome! Im actually about a stones throw from the airport
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Quoting K8eCane:


Are you in Wilmington? Trpicalwx is in Rocky Point


Yep!!
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Quoting ncstorm:


You may be right..I remember that Peter Jennings came and broadcasted from the old Wachovia building downtown with ABC News..


Are you in Wilmington? Trpicalwx is in Rocky Point
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Quoting K8eCane:



It may have. I was in my late teens and i just remember it hitting us and leaving. We thought it was gone and the next night my mom wakes me up trying to pull my bed away from the wall and she was saying the hurricane had come back


You may be right..I remember that Peter Jennings came and broadcasted from the old Wachovia building downtown with ABC News..
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I personally think that 94L is going to shed the NE fetch and redevelop convection overnight. closer to the low which I believe is east of Biscayne Bay.



Lower shear is slowing working North.





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Quoting CosmicEvents:
You can clearly see the exact surface low of 94L now on Miami doppler..
.
.
Link


Is it supposed to be east of Miami?
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Quoting CosmicEvents:
You can clearly see the exact surface low of 94L now on Miami doppler..
.
.
Link



Are you sure thats the main one?
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You can clearly see the exact surface low of 94L now on Miami doppler..
.
.
Link
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Quoting luvthetropics:
Link

Sorry just trying to figure out posting pics



You are doing a good job. Georgia tried to help me but i need a POST PIC FOR DUMMIES
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Quoting GTcooliebai:
Subtropical Storm Alpha (also called Alfa) was a rare off-season subtropical cyclone that hit Georgia in May 1972. It developed from a previously non-tropical cyclone in the western Atlantic Ocean, and initially it moved northeastward off of the Carolinas. The storm turned southwestward due to a building ridge, and concurrently it intensified to become Subtropical Storm Alpha. It later moved ashore near Savannah, and it finally dissipated in the northeast Gulf of Mexico on May 29.


Very good analogue for 94L. It looks like the current system will eventually transition into a tropical cyclone though, as opposed to staying subtropical throughout its entire duration.
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Just wondering, has a storm ever formed and re-formed twice?
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Quoting GTcooliebai:
Subtropical Storm Alpha (also called Alfa) was a rare off-season subtropical cyclone that hit Georgia in May 1972. It developed from a previously non-tropical cyclone in the western Atlantic Ocean, and initially it moved northeastward off of the Carolinas. The storm turned southwestward due to a building ridge, and concurrently it intensified to become Subtropical Storm Alpha. It later moved ashore near Savannah, and it finally dissipated in the northeast Gulf of Mexico on May 29.



That might actually be how 94L might behave...
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Guess this'll be another Alpha except by the time it reaches Savanna, it'll head back to the Carolina's instead of the eastern GOM.
Member Since: May 26, 2007 Posts: 47 Comments: 1270
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Link

Sorry just trying to figure out posting pics
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Quoting LargoFl:
.................94 doesnt look too impressive on radar,at least right now
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Based on radar velocities over the Bahamas, 94L may be upped to 40 knots by 00z.
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Quoting ncstorm:
Hey Everyone..I can honestly say after looking at the Euro that I have never seen a track like that before and the bad part about this is that its being consistent with it..whew!!



Not sure how many rode up and down y'all's coast. Apparently it's rare for a storm to form off the Carolina's to cross Florida and survive in the gulf. Disclaimer: the 34 storm the only storm to cross Florida and make landfall in TX. I know I said that before but it still amazes me. :)

July 24-26th, 1934: The third storm of the season formed off the North Carolina coast on the 21st. It then moved south and southwest across Florida into the eastern Gulf...a move only one
other cyclone on record has ever matched.
It then developed rapidly south of Louisiana on the
24th and struck just north of Corpus Christi (Rockport) on the 25th as a minimal hurricane. Winds
at Corpus Christi gusted to 56 mph as the pressure fell to 29.12". Rockport saw a pressure of
28.79". Twenty-four hour rainfall records were set for July at Falfurrias (4.52" on the 26th) and Fowlerton (4.75" on the 24th) St. Joseph’s Island had a 10.2 foot storm surge. Damage estimates were near $4.5 million, mostly to crops. Nineteen died in Texas due to the storm.



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Quoting ProgressivePulse:


Seems they would make the 48hr circle a little bigger to include where they think the low will be in 48hrs?
The first map is a tropical forecast map. The second a surface map.
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Quoting Tropicsweatherpr:
Also TSR released their May forecast that calls for 13/6/3.

Link



Glad, well not glad Per Se, the cane/major numbers are going up. Thought those were rather low in earlier forecasts.
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Quoting K8eCane:




Thanks for the graphic on that Georgia! I dont know how to post the links and graphics


right click on images, select copy image location, in some cases it might be copy image URL, click on the image button above the comment typing box, and past it there.
It will show up when you post the comment.
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Also TSR released their May forecast that calls for 13/6/3.

Link
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Quoting GTcooliebai:
I think our friend Jedkins is getting hammered I think he lives close to the St. Pete/Clearwater Airport.
im not too far awa from there either,it looks like it hooked out into the bay now,booming like crazy
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Subtropical Storm Alpha (also called Alfa) was a rare off-season subtropical cyclone that hit Georgia in May 1972. It developed from a previously non-tropical cyclone in the western Atlantic Ocean, and initially it moved northeastward off of the Carolinas. The storm turned southwestward due to a building ridge, and concurrently it intensified to become Subtropical Storm Alpha. It later moved ashore near Savannah, and it finally dissipated in the northeast Gulf of Mexico on May 29.

Member Since: August 31, 2009 Posts: 0 Comments: 5628
LinkFound this on our local met blog, thought track was interesting
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Quoting GeorgiaStormz:



Beryl would give NC a day or 2 in between.




Thanks for the graphic on that Georgia! I dont know how to post the links and graphics
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Quoting Progster:
Link

Getting breezy in the Bahamas...


14.9 m/s is about 33mph.
We will see what it peaks at.
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Quoting CosmicEvents:
I agree, and the difference in the 2 maps you posted is the day. The first is for now and the second for 5/26.


Seems they would make the 48hr circle a little bigger to include where they think the low will be in 48hrs?
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Member Since: May 17, 2009 Posts: 2 Comments: 904
Quoting ncstorm:


I remember Diana but I didnt think it hit us twice? I thought it sat out there and did loop to loop and then hit us?



It may have. I was in my late teens and i just remember it hitting us and leaving. We thought it was gone and the next night my mom wakes me up trying to pull my bed away from the wall and she was saying the hurricane had come back
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Link

Getting breezy in the Bahamas...
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Although SSD still has the low in the Florida Bay.
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Quoting ProgressivePulse:
Personally think the low is east of Biscayne Bay.
I agree, and the difference in the 2 maps you posted is the day. The first is for now and the second for 5/26.
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Deep convection is building around the eye again rapidly.

It's definitely possible to see Major Hurricane Bud at 8PM.

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Quoting LargoFl:
its booming in the distance but no rain here yet
I think our friend Jedkins is getting hammered I think he lives close to the St. Pete/Clearwater Airport.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Recon found maximum flight level winds of 120 knots. That's roughly 100 knots at the surface.
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Quoting GTcooliebai:
THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
HILLSBOROUGH COUNTY IN WEST CENTRAL FLORIDA...
PINELLAS COUNTY IN WEST CENTRAL FLORIDA...

* UNTIL 730 PM EDT.

* AT 645 PM EDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR
SAINT PETE CLEARWATER AIRPORT...OR 7 MILES SOUTHWEST OF TAMPA
INTERNATIONAL AIRPORT...AND MOVING NORTHWEST AT 10 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
PINELLAS PARK...SEMINOLE...LARGO...CLEARWATER...DUNEDIN...P ALM
HARBOR...TARPON SPRINGS...SOUTH PASADENA...KENNETH CITY...
WESTCHASE...TREASURE ISLAND...LAKE FERN...HIGHPOINT...MADEIRA
BEACH...OLDSMAR...SAFETY HARBOR...CLEARWATER BEACH...BELLEAIR...
CALADESI ISLAND AND BELLEAIR BEACH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DOPPLER RADAR HAS INDICATED SOME WEAK ROTATION WITHIN THIS STORM.
WHILE NOT IMMEDIATELY LIKELY...A TORNADO MAY STILL DEVELOP. IF A
TORNADO IS SPOTTED...ACT QUICKLY AND MOVE TO A PLACE OF SAFETY IN A
STURDY STRUCTURE...SUCH AS A BASEMENT OR SMALL INTERIOR ROOM.
its booming in the distance but no rain here yet
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Quoting K8eCane:
It was 1984 we got hit twice by Diana. It had a funny track, but not like this one


I remember Diana but I didnt think it hit us twice? I thought it sat out there and did loop to loop and then hit us?
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THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
HILLSBOROUGH COUNTY IN WEST CENTRAL FLORIDA...
PINELLAS COUNTY IN WEST CENTRAL FLORIDA...

* UNTIL 730 PM EDT.

* AT 645 PM EDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR
SAINT PETE CLEARWATER AIRPORT...OR 7 MILES SOUTHWEST OF TAMPA
INTERNATIONAL AIRPORT...AND MOVING NORTHWEST AT 10 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
PINELLAS PARK...SEMINOLE...LARGO...CLEARWATER...DUNEDIN...P ALM
HARBOR...TARPON SPRINGS...SOUTH PASADENA...KENNETH CITY...
WESTCHASE...TREASURE ISLAND...LAKE FERN...HIGHPOINT...MADEIRA
BEACH...OLDSMAR...SAFETY HARBOR...CLEARWATER BEACH...BELLEAIR...
CALADESI ISLAND AND BELLEAIR BEACH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

DOPPLER RADAR HAS INDICATED SOME WEAK ROTATION WITHIN THIS STORM.
WHILE NOT IMMEDIATELY LIKELY...A TORNADO MAY STILL DEVELOP. IF A
TORNADO IS SPOTTED...ACT QUICKLY AND MOVE TO A PLACE OF SAFETY IN A
STURDY STRUCTURE...SUCH AS A BASEMENT OR SMALL INTERIOR ROOM.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting TropicalAnalystwx13:
I just have a feeling it will look much better organized when I wake up in the morning.

Here is what it was at 2pm..........Last advisory update: 2:00 PM EDT, Thu May 24 2012
Lat: 25.3 N Long: 80.4 W
Winds: 40 mph (35 knots)
Pressure: 29.77 inches (1008 mb
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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.