Average hurricane season foreseen by CSU, NOAA, and TSR

By: Dr. Jeff Masters , 4:45 PM GMT on June 02, 2009

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A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued June 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 11 named storms, 5 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 88% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their April forecast, which called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (28% chance, 31% chance is average) and the Gulf Coast (28% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.

The forecasters cited several reasons for an average season:

1) Sea surface temperature (SST) anomalies in the tropical Atlantic are quite cool. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Substantial cooling began in November 2008 (Figure 1), primarily due to a stronger than average Bermuda-Azores High that drove strong trade winds. These strong winds increased the mixing of cool waters to the surface from below, and caused increased evaporational cooling.

2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. This occurs because El Niño conditions bring higher wind shear over the tropical Atlantic. The CSU team expects the current neutral conditions may transition to El Niño conditions (70% chance) by this year's hurricane season. I discussed the possibility of a El Niño conditions developing this year in a blog posted Friday.


Figure 1. Change in Sea Surface Temperature anomaly between November 2008 and 2009. Most of the Atlantic has cooled significantly, relative to normal, over the past 7 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to slightly warm ENSO conditions, slightly below-average tropical Atlantic SSTs, and above-average far North Atlantic SSTs during April-May. Those five years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1965, which had Category 3 Betsy that hit New Orleans; 1960, which had two Category 5 hurricanes, Ethyl and Donna; and 1959, which had Category 3 Hurricane Gracie, which hit South Carolina. The mean activity for these five years was 10 named storms, 6 hurricanes, and 2 intense hurricanes, almost the same as the 2009 CSU forecast.

How accurate are the June forecasts?
The June forecasts by the CSU team have historically offered a skill of 20 - 30% higher than a "no-skill" forecast using climatology (Figure 2). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. This year's June forecast uses the same formula as last year's June forecast, which did quite well predicting the 2008 hurricane season (prediction: 15 named storms, 8 hurricanes, 4 intense hurricanes; observed: 16 named storms, 8 hurricanes, 5 intense hurricanes). An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.44 to 0.58 for their June forecasts, which is respectable.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

NOAA's 2009 hurricane season forecast
The National Oceanic and Atmospheric Administration (NOAA), issued its 2009 Atlantic hurricane season forecast on May 21. NOAA anticipates that an average season it most likely, giving a 50% chance of a near-normal season, 25% chance of an above-normal season, and a 25% chance of a below-normal season. They give a 70% chance that there will be 9 - 14 named storms, 4 - 7 hurricanes, 1 - 3 major hurricanes, and an Accumulated Cyclone Energy (ACE) in the 65% - 130% of normal range. The forecasters cited the following main factors that will influence the coming season:

1) 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).

2) There will either be an El Niño event or neutral conditions in the Equatorial Eastern Pacific. An El Niño event should act to reduce Atlantic hurricane activity. However, our skill at predicting an Niño in late May/early June is poor, so there is high uncertainty about how active the coming hurricane season will be.

3) Cooler-than-average SSTs are currently present in the eastern tropical Atlantic. These cool SSTs are forecast to persist through into August-September-October (ASO). ASO SSTs in the eastern tropical Atlantic have not been below average since 1997. Cooler SSTs in that region are typically associated with a reduction in Atlantic hurricane activity.

Thus, they expect that even though we are in an active hurricane period, the presence of an El Niño or cool SSTs in the eastern Atlantic could easily suppress activity, making a near-average season the most likely possibility. They note that two promising computer models, the NOAA CFS model and the European Center for Medium-Range Weather Forecasts (ECMWF) Global Climate Model System 3, both forecast the possibility of a below-average hurricane season.

2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) has joined the ranks of NOAA and Colorado State University in calling for near-average activity. The latest TSR forecast issued June 4 calls for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are close to the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes, and are sharp reduction from their April forecast of 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 50% chance that this season will be in the bottom 1/3 of years historically, and a 40% chance that U.S. landfalling activity will be in the lowest 1/3 of years historically. TSR gives a 32% chance of a near-normal season, and a 17% chance of a below normal season. TSR rates their skill level as 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.2 named storms will hit the U.S., with 1.3 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 7 - 18% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 0.9 named storms, 0.4 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their reduced forecast: a large and unexpected cooling of sea surface temperatures in the tropical Atlantic, and warmer SSTs in the Equatorial Eastern Pacific (which might lead to an El Niño event that will bring high wind shear to the Atlantic). TSR expects faster than than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.83 meters per second (about 1.7 mph) faster than average in this region, which would create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling. TSR forecasts that SSTs will cool an additional 0.3°C compared to average over the MDR during hurricane season.

Air France crash
The Air France Flight 447 A330 aircraft that disappeared over the mid-Atlantic Ocean yesterday definitely crossed through a thunderstorm complex near the Equator, according to a detailed meteorological analysis by Tim Vasquez. He concludes that "the A330 would have been flying through significant turbulence and thunderstorm activity for about 75 miles (125 km), lasting about 12 minutes of flight time" but that "complexes identical to this one have probably been crossed hundreds of times over the years by other flights without serious incident". See also the excellent CIMSS satellite blog for more images and analysis of the weather during the flight.

Invest 92
NHC is tracking a storm near the Azores Islands (Invest 92L) that is probably the remnants of the core of an extratropical cyclone that closed off some warm air at the center. The system has developed some heavy thunderstorm activity near its center, making this a hybrid storm. However, with ocean temperatures near 62°F (16°C), this storm has little chance of becoming a named subtropical storm.

Jeff Masters

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Quoting StSimonsIslandGAGuy:
The director of the Australian meteorological bureau at the turn of the 19th/20th centuries used to name tropical cyclones after political figures he did not like...giving him the chance to describe them as "causing great distress" or "wandering aimlessly across the Pacific"


Now that's funny! wandering aimlessly ha ha
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Quoting StSimonsIslandGAGuy:


Because it's not a tropical system.


I mean why isn't it a STS or TS?
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Love that post 53, osuguy. Great data and analysis to back up your previous statement; without the attitude that sometimes crops up here. :)

Kudos +1
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Quoting StSimonsIslandGAGuy:
The director of the Australian meteorological bureau at the turn of the 19th/20th centuries used to name tropical cyclones after political figures he did not like...giving him the chance to describe them as "causing great distress" or "wandering aimlessly across the Pacific"


That's still in practice.

Otherwise we wouldn't have a Tropical Storm/Hurricane Gordon... ;)
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Looks like you're about to get a little wet there Pat......

NOLA Radar
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LOL...


02/1800 UTC 44.0N 24.1W ST3.0 92L
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Wait a second, why hasn't 92L become Ana yet? It already has 50 mph winds!
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So although the ITCZ will follow the sun north for the Northern Hemisphere summer...with the pattern of SSTs...it will likely remain much further south than normal = less activity.

The image below shows above normal SSTs along and south of the Equator in the Atlantic with cooler then normal water in the tropical North Atlantic. Thermodynamically, this pattern supports a stronger northerly component to the trade winds high (cold) to low (warm) pressure.

SST anomalies are generally slower to change in the summer...so this means that an abnormally far south ITCZ will likely be a fixture for the 2009 hurricane season.

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52. bcn
Tropical Storm Aznar at Azores?
(sorry for the political joke, any spaniard will understand)
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GOM IR Image Loop
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Right now the ITCZ is hanging around between 0-5°North

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which show are u going to CDL?
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Ya never know what you'll see at a Good Airshow....CatDL.

Something special always seems to pop up when ya least expect it at those.
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They said now they use it to transport pieces for the international space station (ISS)
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We grew up with all that SRT..LOL

I had all the Models,back when models were plastic.
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Hey Pat, I'm going to the Air Force show this weekend. Can I expect to see the Guppy?
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Quoting Unfriendly:
True, shear is strong down farther south, likely preventing a Dean type storm... but my concern is something like an "A" storm we had back in 1992. Little or no shear over the Bahamas, and SSTs are not as cool there. Wouldn't be suprised to see Florida in the crosshairs this year. Good luck, and hope it misses everyone.



Yeah...hopefully no repeat of Andrew...

Andrew was a Cape Verde storm though...and with the ITCZ so far south this year it will be harder for waves to get going - between interaction with South America and reduced Coriolis Effect
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WOW! pat you have so much wisdom up there in that head of yours! you seem to always have an answer!
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If you can understand Spanish, here is the WeatherMan of Antena3TV (it is a Spanish TV channel), talking about weather in Spain, but also about our 92L INVEST (lol). I don't know how to attach a video from Youtube. Then, I leave the link:

Link

I told him about this disturbance yesterday night.
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The Flying Guppy has a Long history.
It was used for the Apollo project,the Saturn 3rd Stage or S-4B was transported to KSC with it.

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speaking of NASA 747
has anyone ever seen this beast?
I saw it at Ellington field in Houston at the Wings over Houston air show... its a beast... the one I saw was actually larger the size of the 747 maybe... it had 4 jet engines but the body was similar to this
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NASA 747 with Shuttle Atlantis atop is Landing now in Columbus,Miss after a flight from San Antonio

FlightAware
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37. bcn
First tropical storm of the year... in my country? Barcelona is not ready.
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Ossqss, I was reading that the material used on composite planes to "lightning proof" them, can't be used on the nose cone where the radar and other electrical systems are. A strike there could be catastrophic. But the report Dr. Masters mentions also indicates that the type of upswelling in this storm probably wouldn't have even been picked up by radar causing the pilot to fly into it.
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Quoting Ossqss:
post 30

Considering the composite material that is used in these newer planes, the lightning theory does carry more potential weight than if a normal older plane was invloved. Albeit, they state the planes are lightning proof. Nothing is lightning proof IMHO. They had a 320 NM radar view and I would think mid-air collision a low probability also. I would think if it were a terrorist act, they would have claimed it by now.


I agree. A terrorist would have claimed by now. And you are absolutely right regarding the composites used in airframes now. Newer aircraft (such as A330s, like this one), are very composite, but they still must use conductive metal throughout the plane. Also, if a lightning strike happens to hit a light on the wingtip, electrical wires connect that light to a power source, which connect to other things... you get the idea. If the strike is powerful enough or polarized right, it can easily fry the avionics and flight control systems. Combine no flight control systems with turbulence... you get the idea.
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True, shear is strong down farther south, likely preventing a Dean type storm... but my concern is something like an "A" storm we had back in 1992. Little or no shear over the Bahamas, and SSTs are not as cool there. Wouldn't be suprised to see Florida in the crosshairs this year. Good luck, and hope it misses everyone.

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post 30

Considering the composite material that is used in these newer planes, the lightning theory does carry more potential weight than if a normal older plane was invloved. Albeit, they state the planes are lightning proof. Nothing is lightning proof IMHO. They had a 320 NM radar view and I would think mid-air collision a low probability also. I would think if it were a terrorist act, they would have claimed it by now.
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'SATELLITE AND MICROWAVE OBSERVATIONS INDICATE THAT THE AREA OF LOW
PRESSURE LOCATED ABOUT 400 MILES NORTH-NORTHEAST OF THE AZORES
ISLANDS HAS ACQUIRED SOME TROPICAL CHARACTERISTICS..'

That's awesome...

I mean, yes palm trees are possible in that area (We have them in extreme SW England); but I didn't think GW was accelerating *that* quickly!

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Quoting Ossqss:
A different question on the unfortunate plane crash that crossed my mind.

What if a massive methane gas discharge from the ocean floor was placed underneath a T-storm with the right vortex in it to lift the methane to high altitude in sufficient density to stall both of the planes engines and impact the planes ability to fly via lift or simply ignite and blow up? Far fetched, but possible?

Geophenomena



‘‘Can a Single Bubble Sink a Ship?’’

The distance traveled (roughly 7 miles vertically) in an already-turbulent thunderstorm would result in most of the methane disappating to a degree that would make it unable to flame out an engine.

More likely is a lightning strike causing an electrical outage (could be something as simple as a wire grounded improperly) and a catastrophic loss of cabin pressure (severe turbulence can do that).
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.
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000
ABNT20 KNHC 021733
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT TUE JUN 2 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
.
SATELLITE AND MICROWAVE OBSERVATIONS INDICATE THAT THE AREA OF LOW
PRESSURE LOCATED ABOUT 400 MILES NORTH-NORTHEAST OF THE AZORES
ISLANDS HAS ACQUIRED SOME TROPICAL CHARACTERISTICS
HOWEVER...THIS
SYSTEM IS MOVING TO THE NORTH-NORTHWEST AT ABOUT 10 MPH OVER
INCREASINGLY COOLER WATERS AND FURTHER DEVELOPMENT...IF
ANY...SHOULD BE SLOW TO OCCUR. THERE IS A LOW CHANCE...LESS THAN
30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL OR SUBTROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

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

$$
FORECASTER BLAKE
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A different question on the unfortunate plane crash that crossed my mind.

What if a massive methane gas discharge from the ocean floor was placed underneath a T-storm with the right vortex in it to lift the methane to high altitude in sufficient density to stall both of the planes engines and impact the planes ability to fly via lift or simply ignite and blow up? Far fetched, but possible?

Geophenomena



‘‘Can a Single Bubble Sink a Ship?’’
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Link

change it to friday or late thursday
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The blog gets a little crazier each yaer... I can only imageine if we had a major hurricane bearing down on NOLA, Houston, Tampa, or any other metro area (sorry if I left your out)how crazy this place would be... probably wouldn't be able to get a word in edge wise
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-- EMC Cyclogenesis Tracking Page --

Model Cycle: 2009060212


12z NAM


06z NAM
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Quoting ChrisDcane:
sorry this is off topic but i am going on a cruse to Cozumel, i just wanted to know if was nice there. TY:) :D


My aunt lived there for a few years and absolutely loved it.
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is the 00utc or the 18utc the lates one?

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Quoting WPBHurricane05:
Post 12- Looks like development will be close to the United States this season.


That's what Bastardi was saying... I can't really disagree.

However, there is a lot of land to interrupt things from getting too intense (minus a storm camping out over the loop current)...which is why something like 85% of the major hurricanes to hit the US form in the MDR.
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Quoting Patrap:
Cozumel 5-day wu-forecast.

One can find a City 5 day by using the Box at the top left of every page

TY iknow that but the beaches r they nice
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Quoting Weather456:


The trough is expected to drift northwestward, over the next 24 hrs and even though a low pressure could form along the trough, development still seems unlikely over the next 28-72 hrs.

Thanks 456. But with shear decreasing and the low level vorticity at the south end of the trough, could we see something?
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Cozumel 5-day wu-forecast.

One can find a City 5 day by using the Box at the top left of every page
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sorry this is off topic but i am going on a cruse to Cozumel, i just wanted to know if was nice there. TY:) :D
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Area forecast discussion
National Weather Service New Orleans la
1046 am CDT Tuesday Jun 2 2009


Previous discussion... /issued 401 am CDT Tuesday Jun 2 2009/


Discussion...
rain chances will be on the increase over the next three days as a
number of disturbances move across the forecast area and interact
with an increasingly moist and unstable atmosphere. The first
disturbance is forecast to impact the area today. The GFS remains
quite aggressive with this feature and generates a few inches
Worth of quantitative precipitation forecast over the coastal waters along with a surface low from
this convective complex. It then tracks this low to the northeast
tonight and Wednesday. Although the GFS has been rather consistent
with this scenario...it looks suspiciously like convective
feedback. The NAM on the other hand is considerably
drier...particularly over land. Then NAM does however forecast
convection over the coastal waters. The European model (ecmwf) also forecasts a
fair bit of convection over the coastal waters today with some
development over land as well. Although the 00z sil sounding was
fairly dry...moisture is expected to begin increasing and
deepening today. Surface dew points in the lower 70s were hugging
the Louisiana coast west of the Mississippi River early this
morning. Plan to indicate chance probability of precipitation across all but the northern
zones today with the highest chances for rain across the coastal
waters and adjacent land areas. Only isolated convection will be
mentioned across northern areas of the forecast area.

Current Coastal Radar ,NOLA
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And we've been hearing that statement repeated by many smart posters on this blog since early May.
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Quoting WPBHurricane05:
Post 12- Looks like development will be close to the United States this season.


Most likely.
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Post 12- Looks like development will be close to the United States this season.
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Admittedly, the CFS Model might be a little bullish with the developing El Nino...but check out the wind shear anomalies across the Atlantic below.

Looks like 2-4 m/s of higher shear over much of the MDR and the Caribbean (4-8 knots)

Certainly enough in an average sense to lessen the overall number of storms.

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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.

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