Unanswered questions concerning Hurricane Isaac

By: Dr. Jeff Masters , 4:35 PM GMT on August 31, 2012

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The top winds of Tropical Depression Isaac have fallen to 25 mph, but the storm continues to be a potent rain-maker as it heads north-northwest at 11 mph into Missouri. Isaac has spawned up to 20 suspected tornadoes, brought storm surges as high as 13.6' to the coast (in Lake Borgne, LA), and dumped 20" of rain at one station in New Orleans. The 13.27" of rain that fell at Hattiesburg, MS broke the record for wettest August in the city's history (previous record: 13.03" in 1987.) Major flooding is occurring on seven rivers in Louisiana and Mississippi. Isaac is being blamed for at least four deaths in the U.S., 24 in Haiti, and five in the Dominican Republic.

A few notable rainfall totals from Isaac, through 11 am EDT on Friday:

20.08" New Orleans, LA
15.02" Marion, MS
13.99" Pascagoula, MS
13.27" Hattiesburg, MS
10.85" Gulfport, MS
10.39" Slidell, LA
10.17" Biloxi, MS
9.85" Mobile, AL
7.38" Pine Bluff, AR
5.95" Baton Rouge, LA

A major reason for Isaac's heavy rainfall totals has been its very slow motion. This slow speed was due to the fact Isaac has been bumping into a ridge of high pressure that is unusually strong, due to the intense drought over the center of the U.S.; strong drought-amplified high pressure areas are very resistant to allowing any low pressure areas to intrude into their domain. The high pressure area was strong enough this week to allow several all-time records for heat this late in the year to be set:

112° on August 29 at Winner, SD
108° on August 29 at Valentine, NE
107° on August 29 at Corpus Christi, TX
97° on August 29 at Denver, CO (2nd highest so late in the year)


Figure 1. Nighttime view of Hurricane Isaac taken at 1:57 am CDT August 29, 2012, by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite. The VIIRS day-night band detects light in a range of wavelengths from green to near-infrared, and uses light intensification to enable the detection of dim signals. In this case, the clouds of Isaac were lit by moonlight. Image credit: NASA.

Isaac's beneficial rains falling in drought-stricken regions
Hurricanes get a lot of attention because of the billions in damage they cost, and the lives they disrupt. AIR Worldwide estimated today that insured damage from Isaac would cost up to $2 billion. This does not include damage to infrastructure or uninsured damage, so the final price tag of Isaac's rampage will be more like $3 - $5 billion. However, Isaac is now dumping beneficial rains over Arkansas, Missouri, Illinois, Indiana, Ohio, and Kentucky--regions stricken by the worst drought since the 1950s or 1930s, depending upon the exact location. These regions need 9 - 18 inches of rain to pull them out of drought. Isaac's 3 - 6 inches of rain will not end the drought, but will put a pretty good dent in it. I expect that 3 - 6 inches of rain for a wide swath of prime agricultural land in extreme drought is probably worth at least $5 billion, when you consider that a recent estimate by a Purdue economist put the cost of the great drought of 2012 at more than $77 billion. Only Hurricane Katrina ($146 billion) and the drought of 1988 ($78 billion) have been more expensive disasters, according to NOAA's National Climatic Data Center. Unfortunately, Isaac's arrival is poorly timed, as the storm is arriving during harvest season. The strong winds associated with the storm will flatten many crops, making it more difficult to harvest them, and Isaac's winds may cost farmers several hundred million dollars due to unharvestable crops. Still, the rains from Isaac will be highly beneficial for the success of the upcoming winter wheat season, and for next year's growing season.


Figure 2. Predicted precipitation for the five-day period ending on Tuesday evening shows that Isaac is expected to bring a large region of 3 - 6 inches of rain (red, orange, and brown colors) to Arkansas, Missouri, Illinois, Indiana, Ohio, and Kentucky. Image credit: NOAA/HPC.


Figure 3. The great drought of 2012 has brought so little rain to the Midwest that some areas require over 15" of rain (dark purple colors) to end the drought. Image credit: NOAA/CPC.

Unanswered questions about Hurricane Isaac

1. Did the passage of Hurricane Isaac stir up oil from the Deepwater Horizon oil spill? Isaac was the first hurricane to pass over the site of the 2010 Deepwater Horizon oil spill. We know that large hurricanes are capable of creating currents in deep water at the bottom of the Gulf of Mexico; Hurricane Ivan caused upwelling currents of 0.5 cm/s at a depth of about 500 meters. In an August 28 article in the Huffington Post, Nick Shay, professor of meteorology and physical oceanography at the University of Miami, said: "Winds will push water away from the center of a storm, which causes an upwelling as the ocean tries to adjust. It brings whatever is near the bottom up higher in the water column and currents can then push it towards the coast." Up to 1 million barrels of oil from the spill are estimated to still be present in the deep water sediment, on beaches, and in the marshes of Louisiana, and it is possible some of this oil will wash up on the Gulf Coast in coming months. The storm surge of Isaac also likely flushed out oil lodged in the coastal marshes of Louisiana, but it is unknown how much of a concern this might be.

2. What's the deal with these super-sized Category 1 and 2 hurricanes that have been hitting the U.S.? The past three landfalling hurricanes in the U.S.--Isaac (2012), Irene (2011), and Ike (2008)--have all been exceptionally large, among the top ten on record for horizontal extent of tropical storm-force winds. Each of these storms had an unusually low pressure characteristic of a storm one full Saffir-Simpson category stronger. Is this the new normal for U.S. hurricanes?

3. Did the new $14.5 billion upgrade to the New Orleans levee system cause worse flooding elsewhere? Whenever a new levee or flood control structure is created, you make someone else's flood problem worse, since the water has to go somewhere. Where did the water was stopped by the new $1.1 billion, 1.8 mile-long Lake Borgne flood barrier on the east side of New Orleans go? Did it flow south and contribute to the overtopping of the levees near Braithwaite? Or did it go north and contribute to the 36 hours of storm surge in excess of 5' observed along the Mississippi coast at Waveland? I posed this question to NHC's storm surge expert Jaime Rhome, and he said it was impossible to know without doing detailed storm surge modeling studies.

4. Can only hurricanes beginning with the letter "I" hit the U.S. now? Isaac (2012), Irene (2011), and Ike (2008) are the last three hurricanes to hit the U.S. It turns out that hurricanes that begin with the letter "I" and "C" have more names on the list of retired hurricanes than any other letter (nine each.) I'm thinking Isaac will get its name retired, letting storms beginning with "I" take over sole possession of first place on the retired storms list.

Hurricane Kirk in the Central Atlantic
Hurricane Kirk intensified into a 105 mph Category 2 hurricane this morning, becoming the 2nd strongest hurricane of the 2012 Atlantic hurricane season. Hurricane Gordon was the only stronger storm; Gordon hit sustained winds of 110 mph just before reaching the Azores Islands on August 18. Kirk has probably peaked in intensity, and is about to move over colder waters and gradually decay. Kirk is not a threat to any land areas.


Figure 4. Morning satellite image of Tropical Storm Leslie.

Tropical Storm Leslie a long-range threat to Bermuda, Canada, and the U.S. East Coast
Tropical Storm Leslie formed on Thursday in the Central Atlantic. Leslie's formation date of August 30 puts 2012 in 2nd place for earliest formation date of the season's 12th tropical storm. Only 1995 had an earlier formation date of the season's 12th storm. With records dating back to 1851, this year is only the second time 8 total storms have formed in August. The other year was 2004, when the first storm of the season formed on August 1 (Alex), and the 8th storm (Hermine) formed on August 29th. Satellite loops show that Leslie has a modest amount of heavy thunderstorm activity, and respectable low-level spiral bands and upper-level outflow. Conditions appear ripe to allow Leslie to intensify into a Category 2 hurricane by Sunday. Fortunately, Hurricane Kirk is weakening the ridge of high pressure to the north of Leslie, and Leslie is expected to turn to the northwest and miss the Lesser Antilles Islands. However, steering currents for Leslie are expected to collapse early next week, as Leslie gets stuck between two upper level lows. The storm will then slowly meander over the open ocean for many days, potentially threatening Bermuda. Leslie will stay stuck until a strong trough of low pressure approaches the U.S. East Coast around September 8. This trough should be strong enough to pull Leslie to the north and then northeast by September 9. At that time, Leslie may be close enough to the coast that the storm will make landfall in New England, Canada, or the Mid-Atlantic states. Leslie could also miss land entirely; this all depends upon the timing and strength of the September 8 trough of low pressure. Regardless, Leslie is expected to bring an extended period of high waves to the U.S. coast. According to NOAA's Wavewatch III model, large swells from Leslie will reach Bermuda by Monday, and arrive along the U.S. East Coast on Tuesday. These waves will be capable of creating dangerous rip currents and beach erosion.

Portlight disaster relief charity responds to Isaac
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, are in Mississippi, helping out with Isaac relief efforts. You can check out their progress or donate to Portlight's disaster relief fund at the portlight.org website.

I'm planning on taking Saturday off, but will have a new post for you on Sunday. Have a great holiday weekend, everyone!

Jeff Masters

Hurricane Isaac Louisiana (apphotos)
People play in the storm surge from Hurricane Isaac, on Lakeshore Drive along Lake Pontchartrain, as the storm nears land, in New Orleans, Tuesday, Aug. 28, 2012. (AP Photo/Gerald Herbert)
Hurricane Isaac Louisiana
Portlight volunteers at Biloxi shelter (Portlight)
Portlight volunteers at Biloxi shelter
Hurricane Isaac Louisiana (apphotos)
Research students from the the University of Alabama measure wind speeds as Hurricane Isaac makes landfall, Wednesday, Aug. 29, 2012, in New Orleans, La. Isaac was packing 80 mph winds, making it a Category 1 hurricane. It came ashore early Tuesday near the mouth of the Mississippi River, driving a wall of water nearly 11 feet high inland and soaking a neck of land that stretches into the Gulf. The storm stalled for several hours before resuming a slow trek inland, and forecasters said that was
Hurricane Isaac Louisiana
TS Isaac (Raine911)
Between the rain bands
TS Isaac

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Good Night everybody! Too much excitement for me. Play nicey nice.

Member Since: July 17, 2009 Posts: 71 Comments: 27108
920. JLPR2
Wow, a lot of people went to bed there. XD

I'll probably stay till the 00z EURO finishes running.

Member Since: Posts: Comments:
Quoting stormpetrol:
Just one more note the Trough has weakened considerably and the ULL to the NE of Leslie is pushing her west or maybe even slightly south of due west!
Lets see if the models pick up on this or not, will be very interesting to see.
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Quoting JLPR2:


That's a lot of yellow. :\


Looks like it needs some Pepsodent.
Member Since: July 17, 2009 Posts: 71 Comments: 27108

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There is zero convective storms near the area of 11pm advisory. I see no spin or banding wrapping into this area.

They are the Pros but something isn't stirring the Kool AID..

Guess we have to wait till first Visible pics in the morning..
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Whew!
Bedtime for me.

Keep on the front foot, y'all.
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Trying to find Leslie's center has worn me out. Tomorrow's images should shed some light into the situation (literally).

Good Night all.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting JustSouthofEquator:


Hello Grothar,

Ernesto also build up a very impressive -80 C ring patterned convection while it was tranversing the E. Carribean. I was so sure it was an eyewall forming. But......, as it turns out, the LLC was completely decoupled and weak. Seems that is the story for most of the mid season storm (except Gordon and Kirk).


Yes, but I don't believe it was ever as strong as this one. You usually see these in Pacific storms.
Member Since: July 17, 2009 Posts: 71 Comments: 27108
Just one more note the Trough has weakened considerably and the ULL to the NE of Leslie is pushing her west or maybe even slightly south of due west!
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Isn't this the same thing that happened with Isaac when he was in the Central Caribbean when the NHC was hesitant on relocating the center further south? I guess they want to see persistence before they jump the gun.
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Quoting stormwatcherCI:
I can understand them not changing the forecast track/models in the short-term but I cannot understand the location they are saying she is. There is nothing at 17.4 N as far as I can tell.


It is hard to see, but it is there. Many times these lows cannot been seen.

It's like the story of the guy who got caught by his wife. He said, "Are you going to believe me or your eyes?"
Member Since: July 17, 2009 Posts: 71 Comments: 27108
The Most Important Thing :

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD MONITOR THE
PROGRESS OF LESLIE.


NHC is doubting...
Member Since: Posts: Comments:
the 8pm NHC tropical storm winds map only has a 5% chance of TS force winds in the northren most islands and a 0% chance for the islands a few miles south of them...i find that crazy
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Almost a full degree off, hahaha. We'll see what morning light has for us. Night All.
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Turning in for the night, everyone have a goodnight, we'll have to trust the NHC as they are usually right, but if and a big IF, if this hits the N Antilles, they need to start the human part of analysis of tropical cyclones instead of relying just on computer models alone, just sayin... Goodnight.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
903. JLPR2
Quoting PRweathercenter:
This makes no sense lol


LESLIE CONTINUING WEST-NORTHWESTWARD...
...EXPECTED TO PASS NORTH OF THE LEEWARD ISLANDS THIS WEEKEND...










WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD MONITOR THE
PROGRESS OF LESLIE




Just in case. XD
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Quoting goalexgo:

Thanks. NHC certainly holding their ground on this.


Yes, they are. Here is an image of the first trough which you can see goes all the way to Florida. The remnants of Isaac is located in the Central US. The trough expected to move Leslie NW then NE is still developing to the North and West of Isaac.

Member Since: July 17, 2009 Posts: 71 Comments: 27108
TRMM pass mentioned in the discussion:

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900. Relix
I... I see nothing at their location. Not even low level flow or any spin or anything. What the heck NHC. They are the pros... repeat x 100. Don't fully agree but they know what they are doing. Their blind trust in models has cost them a bit in the past (anyone remeber Earl?) but I fully trust them. I just don't see anything at their location.
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899. WWPR
Quoting WeatherNerdPR:

O_o
wat


I just don't see her at 17.4. Not wishing her down, but just don't see it.
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Quoting Grothar:
It is possible that Leslie might miss the first trough, and move Leslie a little further to the west in the short term. But the important feature is where the remnants of Isaac will be in a few days. There is another trough which is expected to lift Leslie NW or North. If ex-Isaac remains more inland, it could prevent the trough from moving down as far and allow a more westerly component to Leslie. However, that does not seem likely at the moment. I believe this is the reasoning that they have been keeping the models as they are until they see what the 1st and 2nd trough does.
I can understand them not changing the forecast track/models in the short-term but I cannot understand the location they are saying she is. There is nothing at 17.4 N as far as I can tell.
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The NHC is going with consistency, until they can confirm otherwise by microwave images, ASCAT, OSCAT, SMFR and all the other neat tools they use to locate the center since Recon isn't in there..."SSM/IS OVERPASS AT 2318 UTC
AND A TRMM OVERPASS AT 0030 UTC INDICATED THAT THE CENTER IS STILL
DISPLACED TO THE NORTH OF THE CONVECTION DUE TO CONTINUING
NORTHERLY VERTICAL WIND SHEAR."
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I'm thinking Leslie will take a path similar to Fiona 2010. Intensity is a bit tricky.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
This makes no sense lol


LESLIE CONTINUING WEST-NORTHWESTWARD...
...EXPECTED TO PASS NORTH OF THE LEEWARD ISLANDS THIS WEEKEND...










WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD MONITOR THE
PROGRESS OF LESLIE


Member Since: Posts: Comments:
894. JLPR2
Quoting Grothar:
It is getting intenser and intenser.





That's a lot of yellow. :\
Member Since: Posts: Comments:
It is not moving wnw... its moving more west
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Quoting Grothar:
The oddest thing with this, is that Leslie has an immense core of cold cloud tops. You normally see this in a very strong developing system. That yellow indicates them.





Hello Grothar,

Ernesto also build up a very impressive -80 C ring patterned convection while it was tranversing the E. Carribean. I was so sure it was an eyewall forming. But......, as it turns out, the LLC was completely decoupled and weak. Seems that is the story for most of the mid season storm (except Gordon and Kirk).
Member Since: Posts: Comments:
891. JLPR2
Quoting stormpetrol:


Not saying it won't, but boy they are stuck on models! nuff said!


No evidence against their location so far, if we later get a OSCAT pass or microwave image proving otherwise then they will have to make some changes.
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890. Relix
Oh knew it. NHC.... well they are the pros.
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Quoting Grothar:
It is possible that Leslie might miss the first trough, and move Leslie a little further to the west in the short term. But the important feature is where the remnants of Isaac will be in a few days. There is another trough which is expected to lift Leslie NW or North. If ex-Isaac remains more inland, it could prevent the trough from moving down as far and allow a more westerly component to Leslie. However, that does not seem likely at the moment. I believe this is the reasoning that they have been keeping the models as they are until they see what the 1st and 2nd trough does.

Thanks. NHC certainly holding their ground on this.
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What is the FLORIDA STATE SUPERENSEMBLE?
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Quoting stormpetrol:


Not saying it won't, but boy they are stuck on models! nuff said!


and smfr
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It is getting intenser and intenser.



Member Since: July 17, 2009 Posts: 71 Comments: 27108
good evening :)
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Quoting GTcooliebai:
You're all wrong! :P

...LESLIE CONTINUING WEST-NORTHWESTWARD... ...EXPECTED TO PASS NORTH OF THE LEEWARD ISLANDS THIS WEEKEND...
11:00 PM AST Fri Aug 31
Location: 17.4°N 52.8°W
Moving: WNW at 21 mph
Min pressure: 999 mb
Max sustained: 65 mph


Not saying it won't, but boy they are stuck on models! nuff said!
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Quoting pottery:

NHC, at 10:37 has it at 16.7.

SORRY !
That was weird..., and wrong... maybe they had not updated the statement.....
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882. denni
Quoting Terradad:
I would like to take a minute to send out a big THANK YOU!
to all the wonderful posters on here tonight. Lot's of great stuff, and none of the petty bs that can occur here.

It will be most interesting to see what things look like in the morning.
I second that!
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000
WTNT32 KNHC 010244
TCPAT2

BULLETIN
TROPICAL STORM LESLIE ADVISORY NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
1100 PM AST FRI AUG 31 2012

...LESLIE CONTINUING WEST-NORTHWESTWARD...
...EXPECTED TO PASS NORTH OF THE LEEWARD ISLANDS THIS WEEKEND...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.4N 52.8W
ABOUT 595 MI...955 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD MONITOR THE
PROGRESS OF LESLIE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM AST...0300 UTC...THE CENTER OF TROPICAL STORM LESLIE WAS
LOCATED NEAR LATITUDE 17.4 NORTH...LONGITUDE 52.8 WEST. LESLIE IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 21 MPH...33 KM/H...AND THIS
GENERAL MOTION WITH A SLIGHT DECREASE IN FORWARD SPEED IS EXPECTED
THROUGH SATURDAY NIGHT. A NORTHWESTWARD MOTION IS EXPECTED BY LATE
SUNDAY. ON THE FORECAST TRACK...THE CENTER OF LESLIE IS EXPECTED TO
PASS WELL NORTH OF THE LEEWARD ISLANDS.

MAXIMUM SUSTAINED WINDS ARE NEAR 65 MPH...100 KM/H...WITH HIGHER
GUSTS. SLOW STRENGTHENING IS POSSIBLE DURING THE NEXT 48 HOURS...
AND LESLIE COULD BECOME A HURRICANE BY SUNDAY.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 90 MILES...150 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 999 MB...29.50 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER BEVEN
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Time to put TS warning for the N Antilles and possibly hurricane watches.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
It is possible that Leslie might miss the first trough, and move Leslie a little further to the west in the short term. But the important feature is where the remnants of Isaac will be in a few days. There is another trough which is expected to lift Leslie NW or North. If ex-Isaac remains more inland, it could prevent the trough from moving down as far and allow a more westerly component to Leslie. However, that does not seem likely at the moment. I believe this is the reasoning that they have been keeping the models as they are until they see what the 1st and 2nd trough does.
Member Since: July 17, 2009 Posts: 71 Comments: 27108
Quoting TropicalAnalystwx13:
17.4N? 0.o

O_o
wat
Member Since: July 7, 2010 Posts: 0 Comments: 5725
TROPICAL STORM LESLIE DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
1100 PM AST FRI AUG 31 2012

LESLIE IS PRODUCING A LARGE CENTRAL AREA OF CONVECTION WITH CLOUD
TOPS COLDER THAN -80C. HOWEVER...AN SSM/IS OVERPASS AT 2318 UTC
AND A TRMM OVERPASS AT 0030 UTC INDICATED THAT THE CENTER IS STILL
DISPLACED TO THE NORTH OF THE CONVECTION DUE TO CONTINUING
NORTHERLY VERTICAL WIND SHEAR. SATELLITE INTENSITY ESTIMATES ARE
55 KT FROM TAFB AND 45 KT FROM SAB....AND THE INITIAL INTENSITY
REMAINS 55 KT. ALTHOUGH SHEAR CONTINUES...THE CIRRUS OUTFLOW IS
GOOD IN ALL DIRECTIONS EXCEPT TO THE NORTH.

THE INITIAL MOTION IS 295/18. THE SUBTROPICAL RIDGE NORTH AND
NORTHEAST OF THE STORM SHOULD STEER LESLIE WEST-NORTHWESTWARD FOR
THE NEXT 36 HR. AFTER THAT...THE CYCLONE IS LIKELY TO TURN
NORTHWESTWARD AND THEN NORTHWARD DUE TO A BREAK IN THE RIDGE
CREATED BY A DEVELOPING MID/UPPER-LEVEL LEVEL LOW PRESSURE
SYSTEM...CURRENTLY SEEN IN WATER VAPOR IMAGERY BETWEEN BERMUDA AND
THE EASTERN UNITED STATES. THE FORECAST TRACK THROUGH 72 HR IS AN
UPDATE OF THE PREVIOUS TRACK AND LIES NEAR THE CENTER OF THE TRACK
GUIDANCE ENVELOPE. THE GUIDANCE DIVERGES AFTER 72 HR AS LESLIE IS
EXPECTED TO MOVE INTO AN AREA OF LIGHT STEERING CURRENTS. THE
GFS...GFDL...HWRF...AND CANADIAN MODELS SHOW A SLOW EASTWARD OR
NORTHEASTWARD MOTION DURING THIS PERIOD...WHILE THE ECMWF AND THE
FLORIDA STATE SUPERENSEMBLE SHOW A SLOW NORTHWESTWARD MOTION.
OVERALL...THE GUIDANCE ENVELOPE HAS SHIFTED A LITTLE TO THE EAST
AFTER 72 HR. AS A RESULT...THE NEW FORECAST TRACK IS ALSO NUDGED A
LITTLE TO THE EAST AND SHOWS A SLOW NORTHWARD MOTION BY 120 HR.
HOWEVER...IT LIES ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE TO THE
WEST OF THE CONSENSUS MODELS.

THE GLOBAL MODELS SUGGEST THAT SOME NORTHERLY SHEAR SHOULD PERSIST
FOR THE NEXT 24-48 HR...AND IT IS UNCLEAR IF LESLIE WILL FIND A
REALLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT DURING THIS TIME.
FROM 48-96 HR...THE CYCLONE MOVES NORTH OF AN UPPER-LEVEL RIDGE AND
IS LIKELY TO ENCOUNTER MODERATE/STRONG WESTERLY SHEAR...WHICH AT
THE VERY LEAST SHOULD STOP DEVELOPMENT. THE UPPER-LEVEL WINDS MAY
BECOME MORE FAVORABLE AFTER 96 HR...ALTHOUGH THE ECMWF STILL SHOWS
A RATHER HOSTILE ENVIRONMENT DURING THIS TIME. THE NEW INTENSITY
FORECAST IS THE SAME AS THE PREVIOUS FORECAST...CALLING FOR SLOW
DEVELOPMENT THROUGH 48 HR...LITTLE CHANGE IN STRENGTH AT 72 AND 96
HR...AND SLIGHT STRENGTHENING FROM 96-120 HR. THE FORECAST IS A
BLEND OF THE SHIPS MODEL AND THE INTENSITY CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 17.4N 52.8W 55 KT 65 MPH
12H 01/1200Z 18.3N 54.8W 60 KT 70 MPH
24H 02/0000Z 19.7N 57.4W 60 KT 70 MPH
36H 02/1200Z 21.1N 59.4W 65 KT 75 MPH
48H 03/0000Z 22.6N 60.9W 70 KT 80 MPH
72H 04/0000Z 25.0N 62.0W 70 KT 80 MPH
96H 05/0000Z 26.5N 62.5W 70 KT 80 MPH
120H 06/0000Z 28.0N 62.5W 75 KT 85 MPH

$$
FORECASTER BEVEN
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I would like to take a minute to send out a big THANK YOU!
to all the wonderful posters on here tonight. Lot's of great stuff, and none of the petty bs that can occur here.

It will be most interesting to see what things look like in the morning.
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Quoting PRweathercenter:
I agree, they won't change

NHC, at 10:37 has it at 16.7.
SORRY, bad post....
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You're all wrong! :P

...LESLIE CONTINUING WEST-NORTHWESTWARD... ...EXPECTED TO PASS NORTH OF THE LEEWARD ISLANDS THIS WEEKEND...
11:00 PM AST Fri Aug 31
Location: 17.4°N 52.8°W
Moving: WNW at 21 mph
Min pressure: 999 mb
Max sustained: 65 mph
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Quoting Relix:
NHC at 17.2N at least... so sure of it :P
17.4 52.8 wnw
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872. 7544
Quoting xtremeweathertracker:
Ok i just looked at the funktop imagery with Tropical Forecast points on.....is it my imagination or is the center of Leslie located under those cold cloud tops and well south and west of the NHC forecast points??? Just sayin!!!
yeap the nhc will relocate the coc soon imo
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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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