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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12 hr out



24 hr out



36 hr out



48 hr out

Member Since: August 23, 2008 Posts: 0 Comments: 1918
My prediction of Igor's strength at 5pm.

Winds: 145 mph

Pressure: 938 mbar

Movement: West at 10-15mph
Member Since: August 9, 2009 Posts: 10 Comments: 4898
For the first time since 92l was named, I am actually seeing some visible rotation. Let's hope that high in the gulf holds. Some parts of Texas do not need anymore rain...
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There's still a lot of dry air out in front of Igor - not enough to do it harm as big as the storm is - but maybe enough to keep it at a 4.
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1390. Max1023
Quoting MiamiHurricanes09:
Satellite loops reveal that Igor has been moving generally towards the W with slight wobbles towards the WSW.


He needs to get above 18N, he is still at 17.7.
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Quoting Max1023:


You are about 30-50 mph low on the intensity though. (Everybody was so nothing much there) The problem is a recurve at 70W often hits Canada, as we stick out all the way to 53W.


LOL, you're right. In a deep-layered steering scenario, strength of a hurricane doesn't seem to have a substantial effect on the track scenario. Looking at the CIMSS for 700-850 mb (weak tropical cyclone steering) and CIMSS for say 500-850 mb (strong tropical cyclone steering scenario), the pattern is the same in this case.

I find myself doing better forecasting tropical cyclone decays when it comes to intensificaiton forecasting. When I try to forecast how fast a storm will come up, I am either too low or too high. When I forecast how fast a storm will come down, I do better, like my Earl decay forecast a few days ago, that intensity forecast was dead on (see Figure 3 of this link).
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Satellite loops reveal that Igor has been moving generally towards the W with slight wobbles towards the WSW.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting angiest:


Earl recurved hundreds of miles west of where originally forecast. NHC has generally been good this year, but Earl's first 5 or so days were a major fail.


The trouble with Earl was, as you said, forecasting the point where he would begin turning. I agree that the forecasting was bad with Earl at some points, but NHC overall did relatively well, with an average error of 250 nautical miles in the 5-day range (within NHC's historical track error for that time).

Below (average error for Earl):
Light blue = OFCL
Purple = CMC2
Yellow = GFS interpolated/AVNI
EDIT = Tan = EGRI/UKMET interpolated


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1386. Grothar
Quoting CosmicEvents:
It looks like that graphic track that btwntx08 posted a few days has verified.


I still find that graphic hard to believe!!
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1385. WxLogic
Quoting StormW:




Well Storm... that's a pretty impressive high trying to push and fill the weakness gap. One interesting thing to note is the oval shape of Igor from W to E... so definitely won't be surprised of a longer W heading before a WNW materializes.

You can also see this in the last 6hrs of the steering:



I know the above is a 200MB to 700MB Steering current... but it is to show the DLM High guiding Igor W and you and also see the DLM High over E CONUS attempting to bridge with it. If this bridge is stronger than expected due to a possible weaker or quicker lift of the TROF then there might be issues down the road.
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Quoting btwntx08:
off topic but the texans are beating the colts 27-10 almost half way though the 4th qtr anyways back tropics


yeah but this game is like the tropics...ANYTHING can happen...lol
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Looking at the water vapor, it appears to me that Igor should start moving more north around 20N, 55W. I think Igor takes a NW turn due to the second trough, then as a ridge builds, Igor may steer WNW south of Bermuda. After that, It's up in the air what else could happen. Another trough may recurve it, that being the best scenario to look at right now, or a weak trough lifts it north along the East Coast.
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For those that would like daily quick tropical updates for the swfl area,you can find mine at sarasotaweather on twitter,92l's heading for haiti over the next 24hrs,look for a more northerly component short term......
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1381. Vero1
Member Since: July 21, 2008 Posts: 4 Comments: 2233
And models have a really hard time predicting tropical storm intensity.
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1379. KEEPEROFTHEGATE (Mod)
011L/MH/I/C4
MARK
17.75N/46.25W
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1378. Max1023
Quoting NCHurricane2009:


I disagree, I think its actually easy to do for Igor, although the next pair of troughs won't buckle Igor significantly northward, they may be just what we need for this to happen (see my blog post for more)


You are about 30-50 mph low on the intensity though. (Everybody was so nothing much there) The problem is a recurve at 70W often hits Canada, as we stick out all the way to 53W.
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Amazing to think Igor was a TS yesterday at this time and now a Cat 4. What is the possibility of him 'creating his own environment' as I have heard mentioned and the trough will not impact him?
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1375. Walshy
Models always seem to have a poleward bias to going north to early.

surprise, surprise...

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1373. Max1023
That ADT will go back up soon, they eye is still warming which almost never happenes in a weakening system, in fact if earl had peaked the eye would become undercast and cool before the eyewall weakened significantly. The .1 drop was caused by a drop of LESS THAN 1 degree in the average eyewall temp, which seems odd as the eyewall looks cooler and more uniform then it did an hour ago when 6.6 was showing. ADT is a bit sketchy with a system this strong, it works best around 6.0 imho.
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1372. angiest
Quoting CosmicEvents:
It looks like that graphic track that btwntx08 posted a few days has verified.


It was very graphic.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting Max1023:
Right now the bast possible track is a recurve near 70W - the models are having Bermuda take a Category 4 Hurricane right now. Igor needs to go west of Bermuda and east of the carolinas and somehow miss Atlantic Canada while he's at it. Hard to do from his position.


I disagree, I think its actually easy to do for Igor, although the next pair of troughs won't buckle Igor significantly northward, they may be just what we need for this to happen (see my blog post for more)
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1370. IKE
Quoting MZT:

I wouldn't go that far. Computers are good at removing human biases, they just crunch the data. Humans have a tendency to say "This looks like the situation of storm XXX in the year 19ZZ and so it'll do the same thing".

The NHC cites model predictions regularly in their outlooks. And they have a good record of being right.


And the same models(GFS...CMC...ECMWF and NOGAPS), that get hammered on here, have successfully predicted 92L's problems...so far...

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1369. pottery
I have just learned that the Enrollment for Bustcasters Annonymous is closed..
too many applicants, apparently.
Member Since: October 24, 2005 Posts: 0 Comments: 24033
Quoting TerraNova:


If there's one track that's been performing great this year it's the NHC official forecast. They did very well with Earl and Danielle, both of which recurved.


You're right. When I said 'the models', I really meant the NHC forecast. It's been very impressive.
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1366. angiest
Quoting btwntx08:
off topic but the texans are beating the colts 27-10 almost half way though the 4th qtr anyways back tropics


and no Rosencopter!
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1365. Max1023
Quoting StormW:




Very soon that trough will give Igor a poleward outflow channel. That pretty much adds 15-20 knots of extra intensity all else being equal.
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CI# /Pressure/ Vmax
6.4 / 939.6mb/124.6kt


Final T# Adj T# Raw T#
6.4 6.5 6.5
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1362. Levi32
Quoting MZT:

I wouldn't go that far. Computers are good at removing human biases, they just crunch the data. Humans have a tendency to say "This looks like the situation of storm XXX in the year 19ZZ and so it'll do the same thing".

The NHC cites model predictions regularly in their outlooks. And they have a good record of being right.


Actually that's almost never done anymore in professional Meteorology at the government level. You're thinking of random bloggers pulling up hurricanes that passed within 100 miles of a storm and made landfall. That has no logical basis. They're not looking at analogs. Looking at things that have happened before requires looking at the overall pattern to see if it fits, and if it does, it can provide valuable insight, and very few Meteorologists actually practice that anymore, but they should.
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Quoting TerraNova:


If there's one track that's been performing great this year it's the NHC official forecast. They did very well with Earl and Danielle, both of which recurved.


Exactly, TN. Models did shift westwards, but the NHC had an excellent handle on them - impressed really. Not always perfect, but no reason to discount them either. Sharp team with all the sharp tools and information.

My concern is that we've still 1/2 the season to go and the tropics are steadily shooting bullets at us -granted, some have been blanks. But, take Hermine for instance, a surprise for many and it wound up taking life and destroying property. So, it doesn't take a landfalling Cat 5 - it can be deadly just as TS or TD even, dropping dangerous winds and rain.
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1359. Max1023
Quoting angiest:


Earl recurved hundreds of miles west of where originally forecast. NHC has generally been good this year, but Earl's first 5 or so days were a major fail.


5 day track errors are huge anyway, compounded by them both undergoing RI when it wasn't forecast a 500 mile error is about average. Igor is not 50 knots stronger than the NHC thought it would be at this position just 18 hours ago, that changes the track forecast a lot simply due to the different steering layers coming into play.
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1358. dmaddox
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It looks like that graphic track that btwntx08 posted a few days has verified.
Member Since: August 3, 2005 Posts: 10 Comments: 5528
1356. A4Guy
Quoting TerraNova:


If there's one track that's been performing great this year it's the NHC official forecast. They did very well with Earl and Danielle, both of which recurved.



Agreed...but run the graphics archive loops on Earl and you can see how the forecast changes over time. 2-3 days out...always spot on...but the margin of error widens considerably on days 4 and 5.
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1355. MZT
Quoting Levi32:
we'll probably end up proving for the millionth time that our human brains are better at forecasting than the computers we created

I wouldn't go that far. Computers are good at removing human biases, they just crunch the data. Humans have a tendency to say "This looks like the situation of storm XXX in the year 19ZZ and so it'll do the same thing".

The NHC cites model predictions regularly in their outlooks. And they have a good record of being right.
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1354. cknltl
Pimples... A rapid growth spurt... Why won't Igor just go to his room and slam the door like every other growing boy with a temper?
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Quoting Levi32:
I'm gonna put this up to prove a point. See the model consensus, including the GFS ensemble members? Impressive right? Infallable....right? Igor must recurve near 60-65W near Bermuda then, right?

No. Watch Igor run farther west before recurving like Earl did, and we'll probably end up proving for the millionth time that our human brains are better at forecasting than the computers we created. This kind of a consensus looks like a completely confident forecast, but watch it go wrong by several hundred miles.

I don't care if it's not a US landfall. It doesn't have to hit land for the model consensus to be wrong. We'll see how it goes.



This has probably been said hundreds of times before, but in the end computers are still inferior to the reasoning of a real person. We've got the NHC, and they've historically outperformed most if not all of the models.
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1352. angiest
Quoting TerraNova:


If there's one track that's been performing great this year it's the NHC official forecast. They did very well with Earl and Danielle, both of which recurved.


Earl recurved hundreds of miles west of where originally forecast. NHC has generally been good this year, but Earl's first 5 or so days were a major fail.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1351. Max1023
Right now the bast possible track is a recurve near 70W - the models are having Bermuda take a Category 4 Hurricane right now. Igor needs to go west of Bermuda and east of the carolinas and somehow miss Atlantic Canada while he's at it. Hard to do from his position.
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Quoting NCHurricane2009:


On my blog post last evening, I was hinting at a pass just southwest of Bermuda, with a turn to the north between Bermuda and the US East Coast.


Oops, here is the link to the projected path I made last night.
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1349. dmaddox
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Quoting yonzabam:
I'm getting deja vu, here. This is Earl all over again.

"It's going west of the models."

"if it gets to 75W, it'll hit the Carolinas."

"The trough is moving too slowly. It ain't gonna reach."

"Any chance of it hitting Florida?"

"No, it's going to New York."

Models have been excellent this year, with regard to tracks. I've given up disagreeing with them. Intensity forecasts are still a joke, though



If there's one track that's been performing great this year it's the NHC official forecast. They did very well with Earl and Danielle, both of which recurved.
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Quoting KanKunKid:
First it was cheesecake, now donuts.

I'll be back. Tracking Igor is gonna be hard on my diet!

I'm snarffing chocolate!!! LOTS of chocolate. Also, (yep I know not on point, but) GO DOLPHINS!
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Quoting WeatherMum:
Just pulled pumpkin chocolate chip cookies out of the oven. Other than that, I'm as sweet as you're going to get....it's my day OFF ! LOL.

Are you in the CONUS?
I'll be right over.
Sounds delicious!
Member Since: August 3, 2005 Posts: 10 Comments: 5528

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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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