CSU predicts a very active hurricane season: 16 storms, 9 hurricanes

By: Dr. Jeff Masters , 4:30 PM GMT on June 01, 2011

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A very active Atlantic hurricane season is on tap for 2011, according to the seasonal hurricane forecast issued June 1 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 166% 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 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is identical to their April forecast. The forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 61% (42% is average.)

The forecasters cited four main reasons for an active season:

1) Neutral to weak La Niña conditions are expected during the most active portion of this year's hurricane season (August-October). This should lead to average to below average levels of vertical wind shear.

2) Above average May sea surface temperatures in the tropical Atlantic.

3) Below average surface pressures during May in the tropical Atlantic.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.

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 weak La Niña conditions in the equatorial Eastern Pacific, and above-average tropical Atlantic and far north Atlantic SSTs during April - May. Those five years were 2008, which featured Hurricane Ike and Hurricane Gustav; 1996, which had two hurricanes that hit North Carolina, Fran and Bertha; 1989, which featured Category 5 Hurricane Hugo; 1981, a very average year with 12 named storms, 7 hurricanes, and 3 intense hurricanes; and 1951, a year that featured 6 major hurricanes. The mean activity for these five years was 12 named storms, 8 hurricanes, and 4 intense hurricanes.

How accurate are the June forecasts?
The June forecasts by the CSU team between 1998 and 2009 had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). 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. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes cause 80% - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses a brand new formula never tried before, so there is no way to evaluate its performance. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.41 to 0.62 for their June forecasts made between 1984 and 2010, which is respectable.


Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.


Figure 2. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2001-2010, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2001 - 2010 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

TSR predicts 25% more activity than normal
Expect the Atlantic hurricane season to be about 25% more active than usual, the British private forecasting firm Tropical Storm Risk, Inc. (TSR) said in their pre-season forecast issued on May 24. TSR calls for 14.2 named storms, 7.6 hurricanes, 3.6 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 124, which is 22% above average. Their May 24 forecast numbers are very close to their previous forecast issued in April. TSR predicts a moderate 55% chance that activity will rank in the top 1/3 of years historically, and a 59% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 16-25% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.

TSR projects that 4.4 named storms will hit the U.S., with 1.9 of these being hurricanes. The averages from the 1950-2010 climatology are 3.1 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 7 - 11% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.3 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their forecast of an active season:

1) Their model predicts that sea surface temperatures will be 0.11°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. They define this as the area between 10°N and 20°N, between the coast of Africa and Lesser Antilles Islands (20°W and 60°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)

2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 0.19 meters per second (about 0.4 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.

FSU predicts a very active hurricane season: 17 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their third annual Atlantic hurricane season forecast today. This year's forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE) of 163. They cite warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation as the major factors influencing their forecast.

Other seasonal forecasts
The UK Met Office's Glosea4 model is predicting a moderately more active season than normal, with 13 named storms and a ACE index of 151. The Cuba Institute of Meteorology is calling for 13 named storms and 7 hurricanes. NOAA predicts 15 named storms, 8 hurricanes, and 4.5 intense hurricanes. Pennsylvania State University predicts 16 named storms.

A surprise tropical disturbance for Florida
The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure and winds have leveled out at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds peaked at 19 mph, gusting to 22 mph, at 10:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. A Windsat pass this morning did not show a closed circulation, and I doubt 93L has enough time to develop into a tropical depression before landfall in Florida. The coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph this afternoon, though.


Figure 3. Afternoon radar image of 93L from the Melbourne, Florida radar.

Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico. The Hurricane Hunters are on call to fly into 93L Thursday afternoon at 2pm EDT, if necessary.

Central Caribbean disturbance
Moisture and heavy thunderstorm activity continues to slowly increase in the region between Central America and Jamaica, and wind shear is falling. With wind shear now 20 - 30 knots, we can expect this disturbance to show increased organization today, and recent satellite images show the beginnings of a surface circulation trying to get going about 100 miles off the coast of Northeast Nicaragua. All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them Thursday through Saturday this week.


Figure 4. Satellite image of the Central Caribbean disturbance.

Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, tomorrow (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. Welcome to the hurricane season of 2011!

Jeff Masters

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1093. Patrap
The Floater isnt gone,,its been moved Left to account for the Movement today.


93L Floater
Member Since: July 3, 2005 Posts: 414 Comments: 125492
the 8pm TWO said that 93L is screwed and PRE-94L will be up graded soon
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Oh... and please don't assume that you can't forecast a storm based on it's name. Just because nobody ever has doesn't mean it's impossible.
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Quoting PSLFLCaneVet:


Hehehehe Good one, Pat. :)


LOLOl, hello Vet, it's been a fun day....and I dont care if the fat folks are singing or the floater is gone....I'm still hopeful for some rain for these folks...
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1089. Patrap
Hiccup

Member Since: July 3, 2005 Posts: 414 Comments: 125492
Quoting AussieStorm:
FYI. The Barometer Bob, Eye on the Hurricane June 1st show will be starting @ 8pm ET. Guest is Brian LaMarre. Brian is the MIC/NWS Tampa Can find it here
Put your username as the username you use here.
I'm there now.

StormW will be on the show soon, come watch. enjoy. Can also watch here.
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Quoting KoritheMan:


Short answer: convection isn't everything.



Roger that, Kori.
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From my predictions May 19, 2011:
Utilizing the latest in storm name-based prediction technology.

Arlene - a Mid-June surprise for the Texas Gulf Coast. Arlene will start as a mild depression (like most Arlenes) but will quickly form into a strong Cat-1 hurricane that makes landfall around Corpus Christi. The heavy rain is a relief to drought stricken Texas. Arlene will pass through San Antonio and Austin... then rain itself out in the Texas Hill Country. Hurricane Arlene will make news for breaking the Texas drought.

In order to rate this new "break-through" prediction method, we need some sort of accuracy grading scale.
How about 10-point scale.
0-5 points awarded for path or landfall forecasting
0-5 points awarded for intensity forecasting.

If MY method achieves an overall score of >35% accuracy this season... does THAT beat Dr. Gray or NOAA's accuracy %? Naturally, they only forecast total #'s, while the naming method attempts to predict path & intensity in addition to overall #'s... so by going so far out on that limb, I'd be happy with a 35%. :>)
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Quoting KEEPEROFTHEGATE:



Keeper is in fine form, today. :)
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1083. xcool
scott39 .hey hey ;)~~~~
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Tornado Damage in Massachusetts

http://boston.cbslocal.com/photo-galleries/2011/0 6/01/tornado-severe-storms-tear-through-massachuse tts/
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whats go overe the rulse so we dont get banned this year


Due to the high amount of traffic that Dr. Masters' blog receives, a special community standard has been established for the blog. The following list comprises the "Rules of the Road" for Dr. Masters' blog.

Keep it civil. Personal attacks, bickering, flaming, and general trollish behavior will not be tolerated. Disagreements are fine, but keep them civil and short.
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Do not circumvent a ban. Most bans last 24 hours or less, please accept the ban. If you create a new username to circumvent a ban, you will be blocked from the site completely.
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Do not "1st!", "1st post!", or any of the numerical/linguistic derivatives. This is a worthless use of blog space.
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Seriously, no spamming. Spamming includes but is not limited to, trying to sell products, trying to solicit traffic for your own blog, trying to solicit traffic for other commercial entities, etc. Do not post links to your own site unless they are directly relevant and even then, use sparingly.




all so plzs note of this


During active periods of hurricane season, these rules will be strictly enforced. Violations will be met with a minimum 24 hour ban.
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1080. scott39
Long time no see Xcool!
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Quoting alfabob:
I still don't understand why NHC gives a storm a higher chance when it doesn't look that great, and then after it has convection going for a while they lower it.


Short answer: convection isn't everything.
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Quoting Patrap:


Hehehehe Good one, Pat. :)
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1077. Patrap
All Atlantic Floaters
Member Since: July 3, 2005 Posts: 414 Comments: 125492
1076. scott39
Quoting IKE:


I knew that picture would surface eventually!! LMAO
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1075. Patrap
Dey be done moved da Floater



Member Since: July 3, 2005 Posts: 414 Comments: 125492
Quoting alfabob:
I still don't understand why NHC gives a storm a higher chance when it doesn't look that great, and then after it has convection going for a while they lower it. 93L was at 30% before the coast, and is probably around twice (x2.5 even) the size now and back over water; but for some reason 10%. Just wait until the LLC and MCV become fully detached and the winds start wrapping around better.. that is what they are calling a trough.


I'm with you, Bob....hanging in there :]
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1073. IKE

Quoting scott39:
This Fat Man is singing right now!!

Member Since: June 9, 2005 Posts: 23 Comments: 37858
1072. xcool
lmao
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1071. scott39
This Fat Man is singing right now!!
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Yes Taz i agree totally
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No drought relief for me from 93L. Oh well. I didn't expect much anyway.
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93L RIP
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Quoting Levi32:
The Caribbean system is having to fight with what's northeast of it. A pair of tropical waves brought a flood of moisture northwestward today. The convergence of that moisture has drawn convection away from the main area of low pressure, and secondary extension is forming. This is what the models have been periodically showing would completely dismantle the system by taking all the energy out to the northeast. While for now most of the energy is focused away, as the jetstream retreats it will eventually bundle back with the main circulation. That will take time, and thus development, if it is going to occur, cannot be expected to occur rapidly or soon.

People who are expecting a quick spinner-upper will have their feelings hurt.With these systems you have to wait.And I really do mean "WAIT".
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Mass. tornado damages hundreds of homes
Springfield sees worst of severe weather, nearby areas hit as well

Visit msnbc.com for breaking news, world news, and news about the economy http://www.msnbc.msn.com/id/43242642/ns/weather/

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1064. Bitmap7
Quoting Levi32:
The Caribbean system is having to fight with what's northeast of it. A pair of tropical waves brought a flood of moisture northwestward today. The convergence of that moisture has drawn convection away from the main area of low pressure, and a secondary extension is forming. This is what the models have been periodically showing would completely dismantle the system by taking all the energy out to the northeast. While for now most of the energy is focused away, as the jetstream retreats it will eventually bundle back with the main circulation. That will take time, and thus development, if it is going to occur, cannot be expected to occur rapidly or soon.



This ^^^
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FYI. The Barometer Bob, Eye on the Hurricane June 1st show will be starting @ 8pm ET. Guest is Brian LaMarre. Brian is the MIC/NWS Tampa Can find it here
Put your username as the username you use here.
I'm there now.
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1061. Bitmap7
The visible satellite image of our #2 disturbance in the Caribbean on the nhc cyclone probability map appears to be developing a spin. A large one too. The convective mass at the top seems to be developing a hook and the convection to the south also seems to be developing a hook. They look as if they are curling towards each other. Since its such a large mass, as levi said "its going to take time".
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I have been trying to tell you all day long due to those 2 factors i mention that 93L had no chance to develop..It will be a rain maker for the lower texas coast on friday..No big problem..
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1059. IKE

Quoting MrstormX:
Whenever I see the NHC make a statement like that, it tells me the storm is RIP in their eyes.
We are gathered here today...to honor an invest that gave me .000000 inches of rain. A real teaser.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1058. Patrap
Member Since: July 3, 2005 Posts: 414 Comments: 125492
1057. Levi32
The Caribbean system is having to fight with what's northeast of it. A pair of tropical waves brought a flood of moisture northwestward today. The convergence of that moisture has drawn convection away from the main area of low pressure, and a secondary extension is forming. This is what the models have been periodically showing would completely dismantle the system by taking all the energy out to the northeast. While for now most of the energy is focused away, as the jetstream retreats it will eventually bundle back with the main circulation. That will take time, and thus development, if it is going to occur, cannot be expected to occur rapidly or soon.

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Quoting FLdewey:

I hear someone singing... she seems to be a little bit on the heavy side. :-o
Hehe.Havn't seen you in a minute!
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Whenever I see the NHC make a statement like that, it tells me the storm is RIP in their eyes.
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1054. IKE

Quoting scott39:
I like those BOLD letters much better! Much easier on these old eyes.
Same here.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Inactivity:
...Over the next 48 hours, give both of the systems 12-48 hours an I would guess each one of their precentages would rise in that time period.


93L's probably won't, as it doesn't have very much time before it moves inland again. Lower tropospheric winds associated with the deep-layer ridge draped across the center of the nation are still rather fast.

I'd say it has about 24-36 more hours left before moving back inland again, and the fast forward motion will not allow for much in the way of surface convergence, and thus a closed low-level circulation.
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Something i have been saying all day 93l was not going to develop due to the dry air and the high shear aloft which the weather channel just indicated...This will be a rain makes for lower texas on friday...
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1051. cg2916
No TWD yet
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1050. scott39
Quoting IKE:

I like those BOLD letters much better! Much easier on these old eyes.
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1049. IKE

Quoting FLdewey:

I hear someone singing... she seems to be a little bit on the heavy side. :-o
lol.....she just put her makeup on....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1048. JRRP
hay que ser objetivos....!!!!!!!!!
Member Since: August 16, 2007 Posts: 0 Comments: 5075
Well, I'm not giving up yet.....unless I just watch it to death :P
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1046. IKE

Quoting scott39:
Ike... Do you have your shield activated? Put it down for about 24-72 hours.... so that little blob can rain on someone!
Once again...no rain today.

***considers moving to Seattle***
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Levi32:


Choose "Storm-relative Mean Radial velocity, 0.5 degrees" from the "Select radar type" menu.



Thank you!
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Quoting NICycloneChaser:


Haha, how could anybody be worried about that wee bunny.
I've seen reletivley small storms turn into nasty storms.So don't be fooled.Us your brain...not your eyes.
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About JeffMasters

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