NOAA, TSR, UKMET, PSU, WSI, and WU Community Predict Active Atlantic Hurricane Season

By: Dr. Jeff Masters , 9:11 PM GMT on May 24, 2013

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NOAA forecasts an above-normal and possibly very active Atlantic hurricane season in 2013, in their May 23 outlook. They give a 70% chance of an above-normal season, a 25% chance of an near-normal season, and 5% chance of a below-normal season. They predict a 70% chance that there will be 13 - 20 named storms, 7 - 11 hurricanes, and 3 - 6 major hurricanes, with an Accumulated Cyclone Energy (ACE) 120% - 205% of the median. If we take the midpoint of these numbers, NOAA is calling for 16.5 named storms, 9 hurricanes, 4.5 major hurricanes, and an ACE index 162% of normal. This is well above the 1981 - 2010 average of 12 named storms, 6 hurricanes, and 3 major hurricanes. Hurricane seasons during the active hurricane period 1995 - 2012 have averaged 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median. Only five seasons since the active hurricane period that began in 1995 have not been above normal--including four El Niño years (1997, 2002, 2006, and 2009), and the neutral 2007 season.


Figure 1. Hurricane Michael as seen by NASA's Aqua satellite at 12:20 pm EDT Thursday September 6, 2012. At the time, Michael was a major Category 3 hurricane with 115 mph winds. Hurricane Sandy was the only other major Atlantic hurricane of 2012. Image credit: NASA.

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

1) Above-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 0.4°C above average, and were 0.33°C above the oceans in the remainder of the global tropics. Long-range seasonal computer model forecasts predict a continuation of above-average SSTs in the MDR during much of hurricane season.

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 Multi-decadal Oscillation (AMO).

3) No El Niño event is expected this year. El Niño events tend to suppress Atlantic hurricane activity. Neutral conditions have been present since last summer, and are predicted to remain neutral through hurricane season by most of the El Niño computer forecast models.

NOAA said, "This combination of climate factors historically produces above-normal Atlantic hurricane seasons. The 2013 hurricane season could see activity comparable to some of the very active seasons since 1995." 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. These models include the NOAA Climate Forecast System (CFS), NOAA Geophysical Fluid Dynamics Lab (GFDL) model CM2.1, the European Centre for Medium Range Weather Forecasting (ECMWF) model, the United Kingdom Meteorology (UKMET) office model, and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble.


Figure 2. Graphic from the 2013 NOAA Atlantic hurricane season forecast highlighting the reasons for this year's anticipated active character.

How accurate are NOAA's 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 3. Forecast skill of the TSR, NOAA (National Oceanic and Atmospheric Administration) and CSU (Colorado State University) for the number of hurricanes in the Atlantic during 2003-2012, as a function of lead time. Forecast precision is assessed using the Mean Square Skill Score (MSSS) which is the percentage improvement in mean square error over a climatology forecast (six hurricanes in a given year.) Positive skill indicates that the model performs better than climatology, while a negative skill indicates that it performs worse than climatology. Two different climatologies are used: a fixed 50-year (1950-1999) climatology, and a running prior 10-year climate norm. NOAA does not release seasonal outlooks before late May, and CSU stopped providing quantitative extended-range December hurricane outlooks in 2011. Skill climbs as the hurricane season approaches, with modest skill levels by early June, and good skill levels by early August. Image credit: Tropical Storm Risk, Inc (TSR).

TSR predicts an active hurricane season: 15.3 named storms
The May 24 forecast for the 2013 Atlantic hurricane season made by British private forecasting firm Tropical Storm Risk, Inc. (TSR) calls for an active season with 15.3 named storms, 7.5 hurricanes, 3.4 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 130. The long-term averages for the past 63 years are 11 named storms, 6 hurricanes, 3 intense hurricanes, and an ACE of 103. TSR rates their skill level as modest for these late May forecasts--11% - 25% higher than a "no-skill" forecast made using climatology. TSR predicts a 63% chance that U.S. land falling activity will be above average, a 21% chance it will be near average, and a 16% chance it will be below average. They project that 4.4 named storms will hit the U.S., with 2 of these being hurricanes. The averages from the 1950-2012 climatology are 3.1 named storms and 1.4 hurricanes. They rate their skill at making these late May forecasts for U.S. landfalls just 8% - 12% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.5 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR’s two predictors for their statistical model are the forecast July - September trade wind speed over the Caribbean and tropical North Atlantic, and the forecast August - September 2013 sea surface temperatures in the tropical North Atlantic. Their model is calling for warmer than average SSTs and slower than average trade winds during these periods, and both of these factors should act to increase hurricane and tropical storm activity.

UKMET office predicts a slightly above normal Atlantic hurricane season: 14 named storms
The UKMET office forecast for the 2013 Atlantic hurricane season, issued May 13, calls for slightly above normal activity, with 14 named storms, 9 hurricanes, and an ACE index of 130. In contrast to the statistical models relied upon by CSU, TSR, and NOAA, the UKMET forecast is done strictly using two dynamical global seasonal prediction systems: the Met Office GloSea5 system and ECMWF system 4. In 2012, the Met Office forecast was for 10 tropical storms and an ACE index of 90. The actual numbers were 19 named storms and an ACE index of 123.

WSI predicts an active hurricane season: 16 named storms
The April 8 forecast from the private weather firm WSI (part of The Weather Company, along with The Weather Channel, Weather Central, and The Weather Underground), is calling for an active season with 16 named storms, 9 hurricanes, and 5 intense hurricanes.

Penn State predicts an active hurricane season: 16 named storms
The May 11 forecast made using a statistical model by Penn State's Michael Mann and alumnus Michael Kozar is calling for an active Atlantic hurricane season with 16 named storms, plus or minus 4 storms. Their prediction was made using statistics of how past hurricane seasons have behaved in response to sea surface temperatures (SSTs), the El Niño/La Niña oscillation, the North Atlantic Oscillation (NAO), and other factors. The statistic model assumes that in 2013 the May 0.87°C above average temperatures in the MDR will persist throughout hurricane season, the El Niño phase will be neutral, and the North Atlantic Oscillation (NAO) will be near average.

The PSU team has been making Atlantic hurricane season forecasts since 2007, and these predictions have done pretty well, except for in 2012, when an expected El Niño did not materialize:

2007 prediction: 15 named storms, Actual: 15
2009 prediction: 12.5, named storms, Actual: 9
2010 prediction: 23 named storms, Actual: 19
2011 prediction: 16 named storms, Actual: 19
2012 prediction: 10.5 named storms, Actual: 19

The wunderground community predicts an active hurricane season: 17 named storms
Over 100 members of the wunderground community have submitted their seasonal hurricane forecasts, which are compiled on trHUrrIXC5MMX's blog. The April 28 version of this list called for an average of 17 named storms, 8 hurricanes, and 4 intense hurricanes in the Atlantic. This list will be updated by June 3, so get your forecasts in by then! As usual, I am abstaining from making a hurricane season forecast. I figure there's no sense making a forecast that will be wrong nearly half the time; I prefer to stick to higher-probability forecasts.



NOAA predicts a below-average Eastern Pacific hurricane season: 13.5 named storms
NOAA's pre-season prediction for the Eastern Pacific hurricane season, issued on May 23, calls for a below-average season, with 11 - 16 named storms, 5 - 8 hurricanes, 1 - 4 major hurricanes, and an ACE index 60% - 105% of the median. The mid-point of these ranges gives us a forecast for 13.5 named storms, 6.5 hurricanes, and 2.5 major hurricanes, with an ACE index 82% of average. The 1981 - 2010 averages for the Eastern Pacific hurricane season are 15 named storms, 8 hurricanes, and 4 major hurricanes. So far in 2013, there has already been one named storm. On average, the 2nd storm of the year doesn't form until June 25.

NOAA predicts a below-average Central Pacific hurricane season: 2 tropical cyclones
NOAA's pre-season prediction for the Central Pacific hurricane season, issued on May 22, calls for a below-average season, with 1 - 3 tropical cyclones. An average season has 4 - 5 tropical cyclones, which include tropical depressions, tropical storms, and hurricanes. Hawaii is the primary land area affected by Central Pacific tropical cyclones.

The week ahead: 91E, and a heavy rainfall threat to Mexico
We're already behind last year's pace for named storms in both the Atlantic (where Tropical Storm Alberto formed on May 19, and Tropical Storm Beryl on May 26), and in the Eastern Pacific, where Bud formed on May 21 (the earliest date since record keeping began in 1949 for formation of the season's second named storm.) The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, is currently located in the Eastern Pacific. The MJO is relatively weak, but is helping boost the chances that Invest 91E in the Eastern Pacific will develop. On Friday, NHC was giving 91E a 20% of developing into a tropical cyclone by Sunday. The 12Z Friday runs of the GFS and ECMWF models were predicting that a weak circulation off the coast of Costa Rica, well east of the separate circulation currently called 91E, could develop into a tropical depression by Tuesday. This system is a threat to spread heavy rains to the coast of Mexico from Acapulco to Guatemala on Tuesday and Wednesday.

In the Atlantic, the models are depicting high wind shear through June 1 over the majority of the regions we typically see May tropical cyclone development--the Caribbean, Gulf of Mexico, and Bahamas. The GFS model is showing a decrease in wind shear over the Western Caribbean after June 1, which would argue for an increased chance of tropical storm development then (though wind shear forecasts more than 7 days in advance are highly unreliable.) The prospects for an early June named storm in the Atlantic are probably above average, though, given that the MJO may be active in the Atlantic during the first week of June.

Have a great holiday weekend, everyone!

Jeff Masters

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Quoting Tropicsweatherpr:
Is cloud cover causing the MDR to drop a little bit?



Probably. No lack of moisture in the tropics, that's for sure.

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The latest NAM is projecting a 160 knot H25 jet to move ashore the West Coast on Wednesday. A jet disturbance of this intensity is unprecedented for late May.

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Quoting Patrap:


FAMILY COMMUNICATIONS

Your family may not be together when disaster strikes, so plan how you will contact one another. Think about how you will communicate in different situations.Make sure to tell your family and friends that you've listed them as emergency contacts.

Teach family members how to use text messaging (also known as SMS or Short Message Service).


What I have learned through a disaster is that it is better to take a deep breath, calm down, and take things slowly, and to not rush to any decisions. When we had a tornado, my parents couldn't contact each other because the cell towers were jammed and the regular phone lines were umm, nonexistent near my house (I blame the storm). It wasn't until nightfall that we knew that everyone was safe and were able to relay the info to our relatives.
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Quoting Bluestorm5:
I guess I grew up disliking music because of my deafness. I do have cochlear implant so I can hear. I guess music sounds different to me. I don't feel emotions from them.


ah well that makes sense

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Quoting wunderkidcayman:

A really good looking circulation

I don't see any circulation. Maybe I need to clean my glasses
Member Since: September 30, 2007 Posts: 9 Comments: 15998
Is cloud cover causing the MDR to drop a little bit?

Member Since: April 29, 2009 Posts: 75 Comments: 15421
000
FXUS62 KMFL 261819
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
219 PM EDT SUN MAY 26 2013

.LONG TERM (WEDNESDAY-FRIDAY)...
THE CONSENSUS OF THE MODEL GUIDANCE CONTINUES TO INDICATE THAT
DEEPER LAYERED TROPICAL MOISTURE AND THE PERSISTENCE OF A MID TO
UPPER LEVEL TROUGH AFFECTING THE REGION COULD CONTINUE WEDNESDAY
THROUGH FRIDAY WITH SHOWERS AND THUNDERSTORMS INDICATED IN THE
FORECAST. THE CONSENSUS OF THE GUIDANCE INDICATES THAT BY THURSDAY
A BROAD LOW LEVEL AND SURFACE TROUGH POSSIBLY FORMING IN THE
VICINITY OF THE FLORIDA STRAITS. IF THIS FEATURE DEVELOPS STRONG
WINDS ACROSS THE ATLANTIC WATERS COULD REACH NEAR 25 KNOTS...BUT
FOR NOW WINDS HAVE BEEN CAPPED NEAR 21 KNOTS IN THE EXTENDED
FORECAST.
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The Gulf could be above average by tomorrow. I was in the Gulf all day yesterday and I know the water felt like bath water. It doesn't take long for the Gulf to warm at all.

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So until GOES-13 comes back up or GOES-14 moves, we're not going to be able to use the TCFP with much accuracy EAST of what looks like 30W.

The above image is the Percent colder than -40. The same applies for the Cloud-cleared water vapor brightness.



As you can see in both the map and the chart there is a cut off where satellite data is not available due to the position of GOES-14 and is causing an anomalously high percentage of cold cloud tops thus increasing the anomalous cyclogenesis potential.
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1101. ncstorm
12z Nogaps


18z Nogaps
Member Since: August 19, 2006 Posts: 13 Comments: 16317
Things that make you go Hummmm. Stage right I am talking...



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1099. Patrap


FAMILY COMMUNICATIONS

Your family may not be together when disaster strikes, so plan how you will contact one another. Think about how you will communicate in different situations.

Family Communication Tips

Identify a contact such as a friend or relative who lives out-of-state for household members to notify they are safe. It may be easier to make a long-distance phone call than to call across town, so an out-of-town contact may be in a better position to communicate among separated family members.

Be sure every member of your family knows the phone number and has a cell phone, coins or a prepaid phone card to call the emergency contact. If you have a cell phone, program that person(s) as "ICE" (In Case of Emergency) in your phone. If you are in an accident, emergency personnel will often check your ICE listings in order to get a hold of someone you know. Make sure to tell your family and friends that you've listed them as emergency contacts.

Teach family members how to use text messaging (also known as SMS or Short Message Service). Text messages can often get around network disruptions when a phone call might not be able to get through.

Subscribe to alert services. Many communities now have systems that will send instant text alerts or e-mails to let you know about bad weather, road closings, local emergencies, etc. Sign up by visiting your local Office of Emergency Management web site.
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Quoting wunderkidcayman:

A really good looking circulation


Still broad and weak though.
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(delurking)

Cognitive musicology student here. Understanding and analysis of music is linked to neurotransmitter activity in the right center area of the brain, the same place we process what happens when we see something and reach for it. Enjoyment of music is linked to oxytocin activity, which governs memory and attachment. If Bluestorm5 doesn't like music, it's because the brain, in the absence of the usual stimuli, probably processes the music using different parts of the brain not associated with the same neurotransmitters.

(returns to lurking)
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MesoWest Jurupa Valley CA US SGXWFO, Riverside, California (PWS)
Updated: 2:49 PM PDT on May 26, 2013
Partly Cloudy
78 °F
Partly Cloudy
Humidity: 43%
Dew Point: 54 °F
Wind: 4 mph from the West
Wind Gust: 10.0 mph
Pressure: 29.96 in (Falling)
Heat Index: 79 °F
Visibility: 10.0 miles
UV: 6 out of 16
Pollen: 4.70 out of 12
Pollen Forecast new!
Clouds:
Few 5000 ft
(Above Ground Level)
Elevation: 794 ft

Another beautiful day here, Goldilocks weather, just right.
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Seems like the operational GFS is having a difficult time consolidating the large monsoonal gyre into one area of low pressure. It instead breaks off different pieces of vorticity and forms at least 3 individual low pressure areas. They are then shot out to the northeast into a large sprawling high pressure system. This solution seems very awkward and it is probably a result of the GFS not handling the monsoonal circulation very well. The ensembles have had a better grip on the evolving pattern and I'd keep sticking to them for now.

18z GFS

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1094. Dakster
Thanks for good news Grothar....

(sarcasm: on)
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I guess that would also show how thick the eyewall is...

'47 storm again:
If my Diameter of Maximum Wind is 40 nm and the Eye Diameter is 24 nm, then

40-24=16/2=8

So, eyewall would be 8 miles thick (assuming even thickness all the way around).

Quoting mikatnight:


So,

Eye Diameter = (RMW-8)x2

'47 storm w/20 nm RMW = 24 mile wide eye.

Haven't had a chance to fully explore that link you supplied, but I've got it saved. Thanks again. Very helpful.
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Quoting Bluestorm5:
I guess I grew up disliking music because of my deafness. I do have cochlear implant so I can hear. I guess music sounds different to me. I don't feel emotions from them.

Kinda sad though you can't enjoys the sweet sound as we do
Member Since: June 13, 2009 Posts: 2 Comments: 12840
Quoting Civicane49:

A really good looking circulation
Member Since: June 13, 2009 Posts: 2 Comments: 12840
Quoting Hurricanes101:


not that its any of my business, but how can you hate music?
I guess I grew up disliking music because of my deafness. I do have cochlear implant so I can hear. I guess music sounds different to me. I don't feel emotions from them.
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I strongly say we gonna have a storm start from Honduras then to cuba then to S Florida then SE US coast
Member Since: June 13, 2009 Posts: 2 Comments: 12840
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Quoting Doppler22:

Ok, i know that low by California most likely isn't a tropical system but how interesting would that be? A storm hitting S. CA as a few did a long time ago?


NOOOOOOOOOOOOO
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Quoting weathermanwannabe:


I am still trying to do the math; if you have a storm with an RMW of 30nm, I think the diameter of the eye would be around 42 nm (30-8 = 22 x 2 = 44).........Same approx figure as Landsea.


So,

Eye Diameter = (RMW-8)x2

'47 storm w/20 nm RMW = 24 mile wide eye.

Haven't had a chance to fully explore that link you supplied, but I've got it saved. Thanks again. Very helpful.
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1085. Patrap


Three climate factors that strongly control Atlantic hurricane activity are expected to come together to produce an active or extremely active 2013 hurricane season.

These are:

1.A continuation of the atmospheric climate pattern, which includes a strong west African monsoon, that is responsible for the ongoing era of high activity for Atlantic hurricanes that began in 1995;

2.Warmer-than-average water temperatures in the tropical Atlantic Ocean and Caribbean Sea; and

3.El Nino is not expected to develop and suppress hurricane formation.
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Quoting Civicane49:
The GFS has been consistent on showing two storms.
Member Since: August 14, 2010 Posts: 10 Comments: 18962
Quoting Bluestorm5:
I'm a music hater of any type and don't listen to any music. However, it must be awkward for you that I've heard of that song.


not that its any of my business, but how can you hate music?
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Quoting Dragod66:
Hey dudes and dudettes! What is wrong with chat? It wont log me in!


I got in just fine. Try again.
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Quoting MississippiWx:


Lol. I've heard of it, unfortunately. Twas a joke back at TA.
Oh, haha. Hard to tell if it's a joke on Internet. Yeah, never get why people like Justin Bieber...
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1079. ncstorm
276


288


312
Member Since: August 19, 2006 Posts: 13 Comments: 16317
Quoting Bluestorm5:
I'm a music hater of any type and don't listen to any music. However, it must be awkward for you that I've heard of that song.


Lol. I've heard of it, unfortunately. Twas a joke back at TA.
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1077. ncstorm
252 hours

Member Since: August 19, 2006 Posts: 13 Comments: 16317
Quoting MississippiWx:


I've never even heard of that song. Funny how you knew about it. :-/
I'm a music hater of any type and don't listen to any music. However, it must be awkward for you that I've heard of that song.
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Quoting ncstorm:
18z GFS-204 hours


Ummm,same as 12z ECMWF in BOC.
Member Since: April 29, 2009 Posts: 75 Comments: 15421
1074. ncstorm
18z GFS-204 hours
Member Since: August 19, 2006 Posts: 13 Comments: 16317
Quoting ncstorm:
Will the Almanac be right??

June 2013
1st-3rd. Sultry weather.
4th-7th. Big thunderstorms from the Gulf Coast to Carolinas. An early tropical storm is possible in the Gulf of Mexico.


lol its looking plausible!
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1072. ncstorm
Will the Almanac be right??

June 2013
1st-3rd. Sultry weather.
4th-7th. Big thunderstorms from the Gulf Coast to Carolinas. An early tropical storm is possible in the Gulf of Mexico.
Member Since: August 19, 2006 Posts: 13 Comments: 16317
Hey dudes and dudettes! What is wrong with chat? It wont log me in!
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18z GFS shows lowering pressures across the western Atlantic in the beginning of June.

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MESOSCALE DISCUSSION 0809
NWS STORM PREDICTION CENTER NORMAN OK
0503 PM CDT SUN MAY 26 2013

AREAS AFFECTED...PANHANDLE/NWRN TX...FAR WRN OK

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 262203Z - 270000Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...ISOLATED SEVERE WIND/HAIL HAZARDS SHOULD DEVELOP FOR A FEW
HOURS THIS EVENING AS TSTMS INITIATE ALONG THE DRYLINE. MONITORING
FOR POSSIBLE SEVERE TSTM WATCH ISSUANCE.

DISCUSSION...21Z SURFACE ANALYSIS PLACED A LEE SURFACE CYCLONE ALONG
THE E-CNTRL CO/W-CNTRL KS BORDER WITH A DRYLINE ARCING S/SWWD
THROUGH THE ERN TX PANHANDLE TO THE PERMIAN BASIN. HIGH-BASED CU HAS
GROWN IN THE PAST HOUR BOTH ALONG AND W OF THE DRYLINE. WITH VERY
STEEP LAPSE RATES THROUGHOUT THE TROPOSPHERE...THIS CU SHOULD DEEPEN
INTO TSTMS BY 23Z. WITH SLIGHT BACKING OF SURFACE WINDS IN THE KHHF
AND KCDS OBS...MAINTENANCE OF MIDDLE TO UPPER 50S SURFACE DEW POINTS
E OF THE DRYLINE WILL CONTRIBUTE TO MODERATE BUOYANCY WITH MLCAPE OF
1000-2000 J/KG. PRESENCE OF A MODERATE MID-LEVEL SPEED MAX /SAMPLED
IN AMA VWP DATA/ ASSOCIATED WITH A SUBTLE IMPULSE CROSSING THE SRN
ROCKIES IN WATER VAPOR IMAGERY WILL LIKELY YIELD EFFECTIVE SHEAR
SUFFICIENT FOR A FEW SUPERCELLS. GIVEN 35-40 DEG F SURFACE
TEMPERATURE/DEW POINT SPREADS...SEVERE WIND/HAIL WILL BE THE
HAZARDS.

..GRAMS/THOMPSON.. 05/26/2013
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Quoting stormchaser19:


GFS, is fantasy hours but, Yikes!!!The wind shear is almos death in MDR in June 9(So early).....Woow!!!!!!I think GFS is overhiped but Man!!!!





Yeah, I've been noticing that on the very long range of the GFS. It's not really moving up in time yet, so not sure of the accuracy.
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Huh, kinda forgot about the Slight we have for today.



URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 222
NWS STORM PREDICTION CENTER NORMAN OK
350 PM MDT SUN MAY 26 2013

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
PARTS OF CENTRAL AND SOUTHEAST MONTANA
NORTHEAST WYOMING

* EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 350 PM UNTIL
1000 PM MDT.

* PRIMARY THREATS INCLUDE...
SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2
INCHES IN DIAMETER POSSIBLE
A FEW DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 80
STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES NORTHEAST OF
LEWISTOWN MONTANA TO 60 MILES SOUTH SOUTHWEST OF BROADUS MONTANA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU2).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

&&

DISCUSSION...ONGOING STORMS FROM CENTRAL MT INTO NE WY ARE EXPECTED
TO INTENSIFY SOME THE NEXT FEW HOURS AS SURFACE HEATING CONTINUES IN
THE DOWNSTREAM AIR MASS...AND ADDITIONAL STORMS WILL LIKELY DEVELOP
AS THIS AREA IS BRUSHED BY AN EJECTING SPEED MAX OVER THE NRN
ROCKIES. THE COMBINATION OF MODERATE INSTABILITY AND SUFFICIENT
VERTICAL SHEAR WILL SUPPORT THE RISK FOR A FEW SUPERCELLS WITH LARGE
HAIL THE NEXT FEW HOURS. LATER THIS EVENING...STORM MERGERS COULD
LEAD TO THE GROWTH OF A CLUSTER OR LINE SEGMENTS...WITH THE RISK FOR
DAMAGING WINDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 26025.
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1066. KEEPEROFTHEGATE (Mod)
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Quoting MississippiWx:


Absolutely no chance anything develops in that part of the world for a while. The subtropical jet is racing through there at speeds of 60-70kts. That area is a little south of the highest shear. If it comes north, it will be ripped to shreds. If it stays south, it will run into South America. It could eventually provide more energy to the monsoon circulation in the Western Caribbean, however.



GFS, is fantasy hours but, Yikes!!!The wind shear is almost dead in MDR in June 9(So early).....Woow!!!!!!I think GFS is overhiped but Man!!!!



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...SPECIAL FEATURE...

A 1008 MB LOW IS EMBEDDED WITHIN THE MONSOON TROUGH SITUATED NEAR
12N94W...OR WITHIN A COUPLE HUNDRED MILES S OF THE GULF OF
TEHUANTEPEC MOVING SLOWLY NW. THIS LOW HAS A RATHER TIGHT AND
SMALL CIRCULATION AS SEEN IN THE LATEST SATELLITE VISIBLE
IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
180 NM OF THE LOW IN THE NE QUADRANT...AND WITHIN 90 NM OF HE
LOW IN THE NW QUADRANT. THE LOW IS UNDERNEATH THE SW PERIPHERY
OF AN UPPER LEVEL ANTICYCLONE CENTERED OVER GUATEMALA. COMPARED
TO 24 HOURS AGO...IT APPEARS THE LOW HAS ATTAINED MORE MOMEMTUM
IN TERMS OF VORTICITY AS IT CONTINUES PULL FURTHER AWAY FROM THE
MONSOON TROUGH. THERE IS A MEDIUM PROBABILITY OF TROPICAL
CYCLONE FORMATION WITH THIS SYSTEM DURING THE NEXT 48 HOURS. SEE
LATEST TROPICAL WEATHER OUTLOOKS FOR PROBABILITY CONDITIONS
RELATING TO THIS LOW.
Member Since: April 29, 2009 Posts: 75 Comments: 15421
Ok, ncstorm. I've been corrected to never say never. ;-)
Member Since: Posts: Comments:
Quoting Civicane49:
18z GFS at 96 hours:


Ok, i know that low by California most likely isn't a tropical system but how interesting would that be? A storm hitting S. CA as a few did a long time ago?
Member Since: Posts: Comments:
Quoting Civicane49:
18z GFS at 96 hours:


dead
Member Since: June 13, 2009 Posts: 2 Comments: 12840
Quoting GeorgiaStormz:




MUCH better one

Link


Lol. I agree, that one is much better.
Member Since: Posts: Comments:

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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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