92L still a threat to develop; Igor a hurricane; TD 12 forming near Africa

By: Dr. Jeff Masters , 2:18 PM GMT on September 12, 2010

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Tropical disturbance (92L) over the Central Caribbean, a few hundred miles south of the Dominican Republic, remains a threat to develop into a tropical depression. Satellite loops this morning show 92L may be starting to form a surface circulation, and an Air Force Hurricane Hunter aircraft will investigate 92L this afternoon to see if a tropical depression is forming.

The storm has only a modest area of heavy thunderstorm with limited low-level spiral banding and upper-level outflow, thanks to an infusion of dry air last night that disrupted the storm. Long range radar out of Puerto Rico shows that heavy rains are affecting that island, but there is no rotation to the radar echoes evident. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are hot, 29.5°C, and these warm waters extend to great depth. Water vapor satellite loops show a large area of dry air lies to the north and west of 92L, and this dry air could interfere with development at times over the next few days.


Figure 1. Morning satellite image of 92L.

Track forecast for 92L
The disturbance is moving west to west-northwest at 15 mph, and steering currents favor a continuation of this motion for the next three days. Model support for development is scattered. The GFS and NOGAPS models do not develop 92L. The GFDL and ECMWF models predict development, with a track taking 92L into Belize or Mexico's Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches today through Monday morning; southern Haiti can expect similar rains tonight through Monday night, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba can expect rains in the 2 - 4 inch range. Once 92L crosses the Yucatan, the ridge of high pressure steering it is expected to remain in place, forcing 92L to a second landfall in Mexico south of the Texas border.

Intensity forecast for 92L
NHC is putting the odds of 92L developing into a tropical depression by Tuesday at 50%; I'd put them higher, at 70%. However, time is running out for 92L to become a hurricane before hitting the Yucatan Peninsula on Wednesday. Given the current disorganized state of 92L, it would be difficult for it to intensify quickly enough to become a hurricane by then. The storm may also suffer another of its mysterious evening collapses, where it loses most of its heavy thunderstorm activity. However, the SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and water temperatures are certainly warm enough to support development. The main detriment to intensification is likely to be dry air, and 92L could wrap in some of the dry air to its northwest at times, slowing down development. There are a number of research flights being made into 92L this afternoon that should help long-term efforts to make better predictions in the future on whether or not disturbances like this will develop or not.


Figure 2. Morning satellite image of Igor.

Igor
Hurricane Igor appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is low, 5 - 10 knots, and is expected to drop below 5 knots for the next five days. Waters are warm, 28°C, and will warm to 29°C by Wednesday. Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor is undergoing a period of rapid intensification today, and will probably be a Category 3 or 4 hurricane by Monday.

The track forecast for Igor remains unchanged. Igor will move west under the influence of a strong ridge of high pressure for the next 2 - 3 days, then turn more to the west-northwest then northwest in response to the steering influence of a broad trough of low pressure moving across the Western Atlantic on Tuesday and Wednesday. This should allow Igor to pass several hundred miles to the northeast of the Lesser Antilles. In the longer range, Igor may be a threat to Bermuda, and does have a small chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 15% of all tropical cyclones that have existed at Igor's current position have gone on to hit the U.S. East Coast; these odds are about 10% for Bermuda and 10% for Canada. The forecast steering pattern for the period 5 - 12 days from now from the ECMWF and GFS models shows a continuation of the pattern we've seen all hurricane season, with regular strong troughs of low pressure moving off the U.S. East Coast. This pattern favors Igor eventually recurving out to sea without affecting any land areas. Recent runs of the ECMWF model indicate that these troughs may not be as intense as previously thought, so it is possible Igor has a higher chance than usual to hit land than climatology suggests. One wild card may be the possible development of TD 12 behind Igor. If TD 12 develops into a hurricane, and moves close to Igor, as some of the models are suggesting, the two hurricanes could rotate around a common center, forcing Igor more towards the coast of the U.S. The long term fate of Igor is difficult to predict at this point.

Tropical Depression Twelve forms
Tropical Depression Twelve formed between the Cape Verdes Islands and coast of Africa this morning, and is already affecting the Cape Verdes with winds near tropical storm strength; sustained winds of 35 mph were recorded in the northwest Cape Verdes this morning. You can follow the progress of TD 12 through the Cape Verdes today using our wundermap.

Next post
I'll have a new post Monday morning, and perhaps late this afternoon if events warrant.

Jeff Masters

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Igor is not annular, but may have similar characteristics. He always had an eastern outflow channel present during his RI stage today, so in my opinion he wasn't annular. Extreme, Igor could definitely become a category five hurricane in the 24-36 hour timeframe, but not before then, he has peaked out right now, and after the EWRC he will peak again.
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Quoting flsky:
Excuse my ignorance, but can anyone tell me just how many Cape Verde systems have hit the U.S. mainland?
Since when?..what time frame are you asking about?
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Quoting StormJunkie:


Evening Dart, good to see you around here.

While this may be true...And I agree there is still plenty of time with Igor. (I assume that's what we are referring to.) I think this is the same mentality of Mrs Lyda Ann Hunkerdown that cost lives on the Bolivar Peninsula. I also think some arguments could be made that this way of thinking may have also cost some lives during Katrina as well.


No question. And they were supposed to learn from that experience. Mnay responders have now put in place protocols that allow for rapid deployment, but I personally feel this allows the NHC to be too conservative.
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3293. Relix
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Quoting DarIvy959810:

good point about 1995


we are currently 5 storms behind 2005, which was up to Ophelia at this point, Phillippe formed on the 17th

looking back at 6 of the busiest seasons so far and seeing where they were on this date

1933: 14 named storms, 7 Hurricanes, 4 Major Hurricanes, 15th storm formed on Sept 16th (21 storms total that season)
1969: 7 named storms, 5 Hurricanes, 4 Major Hurricanes, 8th storm formed on Sept 14th (18 storms total that season)
1995: 13 named storms, 6 Hurricanes, 2 Major Hurricanes, 14th storm formed on Sept 26th (19 storms total that season)
2004: 10 named storms, 6 Hurricanes, 4 Major Hurricanes, 11th storm formed on Sept 16th (15 storms total that season)
2005: 15 named storms, 8 Hurricanes, 4 Major Hurricanes, 16th storm formed on Sept 17th (28 storms total that season)
2008: 10 named storms, 5 Hurricanes, 3 Major Hurricanes, 11th storm formed on Sept 25th (16 storms total that season)

2010: 10 named storms, 4 Hurricanes, 3 Major Hurricanes,
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I agree extreme, I grossly overestimated a system with no strong low level circulation present and that was my bad. Julia and Igor, two cyclones I find hard to believe will affect anyone but Bermuda.
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Have a look at how Igor is effecting the environment around him and even as far away as 30N


Click image for loop.
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Igor 17.6N 47.8 W 150 mph. We need him to move at least to 21 N Worst situation....

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Quoting JLPR2:
Jeez, news weather man are such wishcasters LOL!
I just saw one say that Igor was heading to the NE Caribbean moving straight west, not to be alarmed, but vigilant and he didn't even show the NHC cone. >:| WTH?
@ 13 mph...if he goes any slower he will be moving backwards.
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Quoting DestinJeff:
How can I ignore a word?

Annular.

Let's say that Igor gets blessed as annular. Ok, now what?

Such a fascination with that. Very perplexing.


They're fantastic ACE generators. Mayhap that's the source of said fascination with annulars?
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3283. flsky
Excuse my ignorance, but can anyone tell me just how many Cape Verde systems have hit the U.S. mainland?
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3282. wjdow
Quoting PSLFLCaneVet:
I've learned that the ignore feature works well here. You must make your own choices though. Good evening, btw.


ty. will do.
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Quoting angiest:


XTRP goes through a Hebert Box!!!


That's HeRbert box to you :)
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3278. Gearsts
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Quoting DestinJeff:
How can I ignore a word?

Annular.

Let's say that Igor gets blessed as annular. Ok, now what?

Such a fascination with that. Very perplexing.


Just imagine if it were biannular!
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Quoting TheDawnAwakening:
Igor has become an extremely dangerous category four hurricane of 150mph. It appears the eye of Igor has begun to shrink over the past few hours as cloud tops have begun to shrink. Could be a fluctuation as extreme has just mentioned, but I believe we could be on the brink of an EWRC with Igor. Tough to tell until we get to the morning hours. Update soon to come on Igor and Julia, 92L is not a current threat to develop.


I agree completely. Igor appears to be heading toward an EWRC in its near future. After that I believe we could see this powerful cyclone reach Cat 5. Not too concerned with 92L either. At least not until I see any real signs of development.
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3275. RyanFSU
I suggested two days ago that nothing would stop Igor from becoming a Category 5 and I am a little befuddled that the NHC was so conservative in their forecast. With the almost perfect atmospheric conditions and warm SSTs, Igor was destined to approach its Maximum Potential Intensity (MPI) relatively quickly.

Its explosive development is also an indictment of the dynamical models' intensity predictions which haven't been particular good. Even the overambitious HWRF and GFDL grossly underestimated the RI just 12-18 hours ago.
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Quoting tinkahbell:


That is PERFECT for this blog! LOVE IT!!!!!! it should be the blogs mascot.
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Quoting Herbertsbox:


As a first responder I can tell you that they will hold off until they are absolutely certain there will be some impact. The logistics involved in moving people to places is quite expensive, and I tell you this in the interest of full disclosure--money talks. Until such time as is reasonably necessary, they will be conservative.


Evening Dart, good to see you around here.

While this may be true...And I agree there is still plenty of time with Igor. (I assume that's what we are referring to.) I think this is the same mentality of Mrs Lyda Ann Hunkerdown that cost lives on the Bolivar Peninsula. I also think some arguments could be made that this way of thinking may have also cost some lives during Katrina as well.
Member Since: Posts: Comments:
3272. JLPR2
Jeez, news weather man are such wishcasters LOL!
I just saw one say that Igor was heading to the NE Caribbean moving straight west, not to be alarmed, but vigilant and he didn't even show the NHC cone. >:| WTH?
Member Since: September 4, 2007 Posts: 7 Comments: 8732
Quoting DestinJeff:
Is Igor annular?

Do you think I can mock that question into submission, like The Chart?
Nah.... every time u ask somebody'd answer "not yet". Seriously.

Member Since: October 25, 2005 Posts: 19 Comments: 22307
Sorry about the confusion,local met misspoke,said we had a new td,ment to say new ts,still looks to meet td criteria to me,but what do i know?????,lol
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Quoting Levi32:
Igor is starting to lose some of his annular characteristics.
I agree. He no longer has present that intense ring of strong thunderstorm activity that surrounded the eye a couple of hours ago. He no longer is as symmetric as before, and banding features are beginning to develop.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
3266. JRRP
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HELLO?

that is no wobble...the hurricane is definitely heading wwsw....

on a straight line. Annular.

we have a player gentleman and ladies...

pucker. up...


Katrina, Camille...Andrew time....


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3263. angiest
Quoting StormJunkie:
Evening all

Igor is a nasty little beast...

Ans since it still a ways out, here's a little westcasting humor...

OMG!!!! It's missing the turn! Look at the Xtrap model!



And as a note, for those of you that may want to post the SFWMD model graphic at some point. Copy the image location, but then make sure you change the https to http


XTRP goes through a Hebert Box!!!
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Igor has become an extremely dangerous category four hurricane of 150mph. It appears the eye of Igor has begun to shrink over the past few hours as cloud tops have begun to shrink. Could be a fluctuation as extreme has just mentioned, but I believe we could be on the brink of an EWRC with Igor. Tough to tell until we get to the morning hours. Update soon to come on Igor and Julia, 92L is not a current threat to develop.
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3261. angiest
Quoting GeoffreyWPB:
Don't forget what StormW and Max Mayfield said:

StormW:

"If it's strong enough, and oriented in a certain way, it can, well, not really create it's own high pressure, but it can what we call "pump the ridge"...meaning, if there is a decent enough ridge to it's north, if the outflow of the hurricane is strong enough, the heat it pumps out, will reinforce the ridge to the North and NW of the hurricane enough, that it has a tendency to remain on a more of a WNW or even steady NW course, vice a more poleward motion. That is what we mean when we say the a strong hurricane can modify the environment around it."

Max Mayfield:

A large and strong hurricane can on occasion contribute to building a ridge to the north. Hurricane Gilbert in 1988 was such an example. Some of the models continued to indicate it would turn more toward the north in the Gulf of Mexico and it continued moving west-northwestward instead. Hopefully, the numerical models have improved enough to handle this much better. Examples like Isabel in 2003 and Bill in 2009 turning northward were handled well by the models.




In 1988, Galveston famously ordered an evacuation for Gilbert based on Accuweather's forecast of Gilbert turning north towards a trough.

The question is, can you really fault them for doing that?
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3260. angiest
Quoting GeoffreyWPB:
Don't forget what StormW and Max Mayfield said:

StormW:

"If it's strong enough, and oriented in a certain way, it can, well, not really create it's own high pressure, but it can what we call "pump the ridge"...meaning, if there is a decent enough ridge to it's north, if the outflow of the hurricane is strong enough, the heat it pumps out, will reinforce the ridge to the North and NW of the hurricane enough, that it has a tendency to remain on a more of a WNW or even steady NW course, vice a more poleward motion. That is what we mean when we say the a strong hurricane can modify the environment around it."

Max Mayfield:

A large and strong hurricane can on occasion contribute to building a ridge to the north. Hurricane Gilbert in 1988 was such an example. Some of the models continued to indicate it would turn more toward the north in the Gulf of Mexico and it continued moving west-northwestward instead. Hopefully, the numerical models have improved enough to handle this much better. Examples like Isabel in 2003 and Bill in 2009 turning northward were handled well by the models.




In 1988, Galveston famously ordered an evacuation for Gilbert based on Accuweather's forecast of Gilbert turning north towards a trough.

The question is, can you really fault them for doing that?
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What's the annular index (if any) for Isabel?
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Evening all

Igor is a nasty little beast...

And since it still a ways out, here's a little westcasting humor...

OMG!!!! It's missing the turn! Look at the Xtrap model!



And as a note, for those of you that may want to post the SFWMD model graphic at some point. Copy the image location, but then make sure you change the https to http
Member Since: Posts: Comments:
3257. FLDART1
Quoting Herbertsbox:


As a first responder I can tell you that they will hold off until they are absolutely certain there will be some impact. The logistics involved in moving people to places is quite expensive, and I tell you this in the interest of full disclosure--money talks. Until such time as is reasonably necessary, they will be conservative.
Absolutely correct...
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3255. Levi32
Igor is starting to lose some of his annular characteristics.
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Quoting ChrisDubois:
Looks like Igor has a good chance of becoming Annular with its very large eyewall ( above 14wiles wide) and extremely warm SST's in front of it. Your right Storm W the first trough has missed Igor, and its up to the 2nd one to pick it up. I also see a bend back towards the WNW at the end of the model runs. This one like the others will be interesting come Wednesday


Man today Im on point with my forecast... I guess I got lucky. I wonder if IGOR can strengthen the high pressure above it and continue on a more West Run?
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Quoting weatherwart:
Moving west at 13 mph. There you go. Igor wobbles but he doesn't go south.


With a tenth of a degree drop...if that continues then this will cause a change in the forecast path....that is all everyone is getting at....
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Don't forget what StormW and Max Mayfield said:

StormW:

"If it's strong enough, and oriented in a certain way, it can, well, not really create it's own high pressure, but it can what we call "pump the ridge"...meaning, if there is a decent enough ridge to it's north, if the outflow of the hurricane is strong enough, the heat it pumps out, will reinforce the ridge to the North and NW of the hurricane enough, that it has a tendency to remain on a more of a WNW or even steady NW course, vice a more poleward motion. That is what we mean when we say the a strong hurricane can modify the environment around it."

Max Mayfield:

A large and strong hurricane can on occasion contribute to building a ridge to the north. Hurricane Gilbert in 1988 was such an example. Some of the models continued to indicate it would turn more toward the north in the Gulf of Mexico and it continued moving west-northwestward instead. Hopefully, the numerical models have improved enough to handle this much better. Examples like Isabel in 2003 and Bill in 2009 turning northward were handled well by the models.


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Quoting angiest:


That's old news. ;)


Dang. Came back from the store and thought I found something big.
Member Since: June 9, 2007 Posts: 4 Comments: 15920
Quoting DestinJeff:


I've been looking for a discounted trough. I wonder how much they are asking?
I think I saw them advertised at Big Lots.
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3247. Ldog74
Quoting hunkerdown:
so you are honestly trying to say that only the northern part of the eyewall contracted but the southern part didn't ?? IF that were the case then the eyewall would be significant;y lopsided...try again.


Obviously the entire eyewall contracted, however the eyewall contraction was to the south. That is, the northern part contracted south but stayed the same from an angular perspective. The southern part of the eyewall did not contract north but instead became steeper or tighter from an angular perspective.
Obviously this is how it appears to me, by no means am I communicating directly with the weather gods.
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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.