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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Quoting stormpetrol:
Leslie is different from Ernesto and Isaac IMO , there ain't displacement per se of COC.



Almost perfectly vertical.
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Well...we know where the MLC is.



The LLC will either dissipate or relocate. There's no other option with an MLC that strong.
Member Since: July 6, 2010 Posts: 113 Comments: 33323
The weaker Leslie stays the more west she goes and not will only affect the islands but the U.S will have to start looking at this closely as well.
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Leslie is different from Ernesto and Isaac IMO , there ain't displacement per se of COC.


Member Since: April 29, 2007 Posts: 0 Comments: 8134
668. JLPR2
If I didn't know any better I would say the center is around 16.1n.



Really confusing storm, if this keeps up the circulation should be exposed by tomorrow, there isn't much intense convection above 17n.
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Quoting SLU:
Well the microwave pass supercedes the infrared imagery and you can clearly see the LLC near 17n. The rotation at 16n is the mid-level circulation. In other words, Leslie is very decoupled just like Isaac was in that same area. That is perhaps the strengthening ceased for most of today.

Having said that, it is possible for a new LLC to form further south since the mid-level low seems to be very powerful now.

I agree with you. "Extreme North East Islands" keep a very close on this, you could be in for squally weather Sunday night

Dave
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Quoting washingaway:
Well, I survived another one.......

Does anyone know how Patrap faired?


Presslord was in touch with Pat a couple of times by phone yesterday, and had no major problems to report...


[edit] oops.... I hit the 666 anti-post : (
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting NativeSun:
Pottery, please take a look at the high that is coming of the east coast, its at 1024 and getting stonger also moving east and south and the BH high behind Leselie is moving west and strenghtining and bridging the gap between the two highs. If the center is 17.1 than its moving W/SW. Hope it turns soon, just don't see it for the near future.

Yeah. It's all up in the air as far as I can see right now.

I must say, I don't like it.
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Quoting CybrTeddy:


Yea but people where thinking that might end up as a hurricane into Florida when it died overnight, I can assure you that the disappointment on here was quite abundant. Some things never change. Leslie though is OTS either way, the W-WSW motion you're seeing is actually convection being shunted off to the south some as the LLC is on the northern edge of the convection. I'm not going to call it decoupled though as per the latest microwave pass it appears to have a very well defined circulation + it's not clocking at 22mph like Ernesto and Isaac where. MLC and LLC's don't just decouple for no reason at all, it's usually a combination of trade winds and forward speed.

I wasn't saying that Leslie was moving WSW, I was actually agreeing with you. I wanted to know why the convection is being pushed away from the center. How are trade winds looking in the area?
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Quoting DDR:
Some feeder activity over the islands maybe.

Hey DDR.
Did you notice very heavy rains in Diego at noon, caused a lot of concern that the river would overflow again.

That was the tail end of a feeder from Leslie.
Check the Rainbow loops...
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662. SLU
Well the microwave pass supercedes the infrared imagery and you can clearly see the LLC near 17n. The rotation at 16n is the mid-level circulation. In other words, Leslie is very decoupled just like Isaac was in that same area. That is perhaps why the strengthening ceased for most of today.

Having said that, it is possible for a new LLC to form further south since the mid-level low seems to be very powerful now.

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Pottery, please take a look at the high that is coming of the east coast, its at 1024 and getting stonger also moving east and south and the BH high behind Leselie is moving west and strenghtining and bridging the gap between the two highs. If the center is 17.1 than its moving W/SW. Hope it turns soon, just don't see it for the near future.
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Quoting WeatherNerdPR:

Still sounds non-threatening to me! XD
I'm not going to apologize unless she becomes a major. Or if she decides to smack me in the face.
Here's hoping she stays far far away from us!.I couldn't take a hurricane with the name Leslie serious.But let's not make her angry!.
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DMax approaches
In the morning,
Ding-Dong the bells are gonna chime,
Check out your food stocks,
Secure the shutter-locks,
But get you to the Store on time.

just plagiarising a little song, there....
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Quoting avthunder:
Yeah, I bet she has had your attention! You guys are always the first to feel these storms. Hope for your sake she makes that turn, but does not seem to be happening yet.
thanks and no need to worry as most people would be prepared. After Louis, anything that chugs itself off the coast of Africa has the attention of everyone lols :D
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657. DDR
Some feeder activity over the islands maybe.
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Quoting washingtonian115:
Where is WNPR?.We owe Leslie a apology xD.

Still sounds non-threatening to me! XD
I'm not going to apologize unless she becomes a major. Or if she decides to smack me in the face.
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looks to be moving south of the next plotted point of the track they put on sat pic
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Quoting WeatherNerdPR:
I think Leslie is pulling a Chris 06. A lot of people are expecting a hurricane in the morning, but the circulation and the convection are becoming rather displaced from each other. It's possible that there may be some shear that the CIMSS maps aren't seeing. Why else would this be happening?


Yea but people where thinking that might end up as a hurricane into Florida when it died overnight, I can assure you that the disappointment on here was quite abundant. Some things never change. Leslie though is OTS either way, the W-WSW motion you're seeing is actually convection being shunted off to the south some as the LLC is on the northern edge of the convection. I'm not going to call it decoupled though as per the latest microwave pass it appears to have a very well defined circulation + it's not clocking at 22mph like Ernesto and Isaac where. MLC and LLC's don't just decouple for no reason at all, it's usually a combination of trade winds and forward speed.
Member Since: July 8, 2005 Posts: 259 Comments: 24634
Quoting antiguaboy396:
hmmm well most people here are pretty prepared as a precaution so the surprise warnings shouldnt be too much of a problem. Thanks for the wonderful reply :)
anytime!!, we islanders are very well prepared!

Dave
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Quoting antiguaboy396:
lols no worries. Leslie had our attention since she was a wave coming off of Africa :)
Yeah, I bet she has had your attention! You guys are always the first to feel these storms. Hope for your sake she makes that turn, but does not seem to be happening yet.
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Quoting 1900hurricane:
Looks like a good estimate to me, especially with that hour old microwave pass. For some reason, the convection has slipped away from the center a bit, which can be seen in infrared imagery.

A new center could be forming under that deep convection, only time will tell,tonight could be a very busy night for the NHC, but I think they will go wit with what the microwave pass says 17.1N.

Dave
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Quoting CaribbeanWave:


I'm from St. Croix also,

This dam thing is actually looking like it's moving SW and then West. I thing we might be in trouble. And everyone locally and nationally is saying she will miss us by 400 miles. Not to me.


You are right on buddy, take care of yourself and prepare for it!
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Where is WNPR?.We owe Leslie a apology xD.
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Quoting 1900hurricane:

If you mean a trip of my head to and from the desk repeatedly, then yes, yes it has. :P

heheheh
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Quoting PRweathercenter:
the NHC will take a hard look at the system tonight and the early morning hours of saturday, storms tend to wobble, the mid-level circulation is now going straight west maybe a bit south.

That goes in harmony with the latest steering patterns.

Leslie has pushed more west because she has not gain strength all day, that's bad news for the extreme north-east islands,( Antigua and Barbuda), I would expect," If this trend continues only" that maybe a new center forms further south, it could pass much closer than forecasted. I would not be surprized if a Tropical Storm watch is issued for the those islands sometime tomorrow

Greetings,

Dave
hmmm well most people here are pretty prepared as a precaution so the surprise warnings shouldnt be too much of a problem. Thanks for the wonderful reply :)
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Well, I survived another one. No damage at my place. 72 hours without power and 13 ham sandwiches later, I count my blessings. For I see, many were not as fortunate.

Does anyone know how Patrap faired?
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Quoting pottery:

Yeah, that loop is kind of worrying, isn't it ?
No sign of a north movement there, to my eyes.
Does not conform to the microwave image at all !

Another Isaac ????

This season has been a Trip so far..........

If you mean a trip of my head to and from the desk repeatedly, then yes, yes it has. :P
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Man, I'm gone for a few hours and come back at look at the infrared on Leslie and my eyes totally bugged out. Has the center relocated to the south or something?? She looks wicked strong right now, she has to be nearing hurricane strength. Somebody somewhere better put out a hurricane watch for those people living in the islands!! What in the world are they waiting for??

If those people living on the islands are thinking they have nothing to worry about since the "models" are saying it will go well north they are in for a world of hurt in the morning. The NHC better step up to the plate and admit something is wrong with their projections.
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Quoting GTcooliebai:
I feel ya, a lot of places are water logged and a hurricane would add insult to injury and quite possible bring down large oaks. The roots of my large oak surfaced since last year, I don't think that is a good sign.
Usually when a place is really wet on the coast it can spell trouble for that region.For an example.The gulf coast was wet this year and look what happened?.Isaac came.Last year we were really wet and Irene came and added insult to injury.Now N.C seems to be getting lots of rain.spells trouble if you ask me.Keep a eye open these next few weeks.
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Quoting CASANOVA7823:
Im here looking a the latest infrared images from Leslie and I see that ist not really starting to move northwest or that WNW like how the NWC/NHC says. It seems like that deep high convection is wobbling around the stroms center or relocating and they are following that high cloudtop and assuming that its moving in that direction which appears to be moving WNW but in actuality if you look closely it now seems to be moving SW. I really see a more of a westerly track (Beneath that convection) and it seems like its gaining strength rapidly now. Okay now Im concerned here in St. Croix. When does the HH investigate this one? Does anyone see what I see. Anyone thinks me ought to be concerend with this one?


I'm from St. Croix also,

This dam thing is actually looking like it's moving SW and then West. I thing we might be in trouble. And everyone locally and nationally is saying she will miss us by 400 miles. Not to me.
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Quoting GTcooliebai:
Idk guys, but this seems like another Isaac again. Here take a look at the shortwave loop and check LatLon and Fcst Pts.

Leslie Long Floater - Infrared Channel 2 Imagery Loop

500 mb. vort.


Yeah, that loop is kind of worrying, isn't it ?
No sign of a north movement there, to my eyes.
Does not conform to the microwave image at all !

Another Isaac ????

This season has been a Trip so far..........
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Quoting WeatherNerdPR:

Well, you were the one that mentioned that the mass of convection took a dive to the SW, while the center coordinates show a continuous WNW motion. Just look at the microwave pass. It isn't as well organized as you make it out to be.
Also, could you stop continuously posting those satellite image GIFs? It's nice that they added that feature, but it's making my computer a bit laggy.



We won't stop posting the gifts this be come it makes your computer a little laggy. You need. A faster and newer computer where not going too stop posting some I this be come your computer is a little laggy



You guys are more then welcome too post has many of them gifts has you want there no rules about it that we can post them on here
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Quoting stormchaser19:
Tropical Storm watches is not too far for the north part of Lesser antilles


Hope the models veryfied and turn NW Leslie is in bussines.
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Quoting WeatherNerdPR:

My Algebra teacher. xD

You should listen to her. You may learn straight line projection like aspectre. lol :)
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Quoting TropicalAnalystwx13:

I think we're going to see the LLC relocate to where the MLC is. Both are very vigorous, and I think the LLC would tend to be pulled towards the deepest convection.

Look at the new banding forming as well.


I'm not so sure about a relocation; a low level center that well defined doesn't just go away, which we found out firsthand with Isaac during his trek through the Caribbean. Once again, I must lament that this is occurring at night when visible imagery is unavailable. Vis would definitely be helpful at a moment like this.
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Quoting antiguaboy396:
lols no worries. Leslie had our attention since she was a wave coming off of Africa :)
the NHC will take a hard look at the system tonight and the early morning hours of saturday, storms tend to wobble, the mid-level circulation is now going straight west maybe a bit south.

That goes in harmony with the latest steering patterns.

Leslie has pushed more west because she has not gain strength all day, that's bad news for the extreme north-east islands,( Antigua and Barbuda), I would expect," If this trend continues only" that maybe a new center forms further south, it could pass much closer than forecasted. I would not be surprized if a Tropical Storm watch is issued for the those islands sometime tomorrow

Greetings,

Dave
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Quoting washingtonian115:
Sorry.Don't wanna see a hurricane come my way.Gotta go to home depot and get my supplies again.
I feel ya, a lot of places are water logged and a hurricane would add insult to injury and quite possible bring down large oaks. The roots of my large oak surfaced since last year, I don't think that is a good sign.
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Quoting TropicalAnalystwx13:

What has you in such a bad mood today?

My Algebra teacher. xD
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Quoting WeatherNerdPR:

Well, you were the one that mentioned that the mass of convection took a dive to the SW, while the center coordinates show a continuous WNW motion. Just look at the microwave pass. It isn't as well organized as you make it out to be.
Also, could you stop continuously posting those satellite image GIFs? It's nice that they added that feature, but it's making my computer a bit laggy.

What has you in such a bad mood today?
Member Since: July 6, 2010 Posts: 113 Comments: 33323
Idk guys, but this seems like another Isaac again. Here take a look at the shortwave loop and check LatLon and Fcst Pts.

Leslie Long Floater - Infrared Channel 2 Imagery Loop

500 mb. vort.

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Quoting Methurricanes:
Now imagine a surge moving at 70mph towards the coastline? it would rise 10x faster than Isaacs, Isaac was moving 7mph, New England Hurricane of 1838 moved over 70 mph.
Good night nurse!!! I just moved here from Tornado Alley...what you are describing sounds like the most epic and terrifying waterspout ever to make landfall...I hope that one broke the mold...
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Quoting TropicalAnalystwx13:

Why else would what be happening? The center of circulation is in the NE part of the convection...it's not like it's rapidly becoming exposed or anything, lol.

Well, you were the one that mentioned that the mass of convection took a dive to the SW, while the center coordinates show a continuous WNW motion. Just look at the microwave pass. It isn't as well organized as you make it out to be.
Also, could you stop continuously posting those satellite image GIFs? It's nice that they added that feature, but it's making my computer a bit laggy.
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Quoting rescueguy:
Looks to me on Shortwave that the LLC at 17.1 got ejected out and the MLC has taken over...

Can't tell because of the overall cloud coverage but looking at the overall motion on Dvorak it is moving more westerly again.

Just my observations..

Thats a possibility too.
But the convection is what you are seeing moving west, so unless the centre relocates southward, the convection will most likely head for the LLC.
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Quoting GTcooliebai:
You know Leslie could just keep going west and bust through the trough, especially if that trough flatens out and the high behind it builds and bridges with the Azores high.
Sorry.Don't wanna see a hurricane come my way.Gotta go to home depot and get my supplies again.
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Ion

Iden :this one

Iron

Ira: or this one have the most potential for replacement of Isaac.

Icarius
that are my guesses so far.
Member Since: October 15, 2011 Posts: 0 Comments: 4467
Quoting NativeSun:
Nice trough coming off the east coast, why is it moving so far south? Looks like a big strong high moving east and south and the high behind the storm is moving west to, where will Lesilie go? West or W/SW? Any takers? Have fun.
it will turn wnw and then nw, until it stalls.
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I think the NHC should come out with a special statement just to be on the safe side of things.
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Quoting Relix:


Actually... I looked at the latitudes... Its a 4 degree gap XD! So yeah, it is around 17.1

Yep, that fooled me when I first looked at it too !
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Quoting Methurricanes:
Now imagine a surge moving at 70mph towards the coastline? it would rise 10x faster than Isaacs, Isaac was moving 7mph, New England Hurricane of 1838 moved over 70 mph.


That is not how that works.

You have it backwards.

The faster the forward speed of the storm, the lower the surge will be for the same intensity, because it has much less time to pile up water, also, in most cases after a limit somewhere between 10 and 20mph, the wave action decreases as forward speed increases as well, and for the same reason.

The optimal forward speed is different for each storm depending on it's size and intensity, but in general the faster it's moving the LOWER the wave action and surge...
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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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