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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Quoting will40:


Link
Thanks Link
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ADT showing 6.6 (129 knots) from CIMSS
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Quoting KimberlyB:


I know I know the answer to this question, but I cannot remember and it's been driving me crazy today (cause Ive been here all day lol)

What does "EWRC" stand for?


Eye Wall Replacement Cycle
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Quoting angiest:


EyeWall Replacement Cycle
Quoting CaneAddict:


Eye Wall Replacement Cycle


Thank you very much!

Oh, and I was right.....I did know that! lol
*facepalm*
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Quoting Goldenblack:
I am kinda disagreeing....

Unless I am reading this wrong...looks like he might (albeit it could be temporary) be caught under a tongue of deep layer high pressure....Please correct me if I am looking at this wrong. I'd much rather be proven incorrect on this one.





This will be an interesting test of the models. Remember the initialization is not going to be that good since we have no HH yet.

However, given the setup, I would agree with the northern turn in 24 hours per NHC and model guidance.

What amazes me about the models (well, shouldn't really since I do computational fluid dynamics for a living BUT I know the difficulties) is that they picked up that the next 24 hours would produce a turn so far in advance. I do agree the steering is subtle and on the surface looks to be immovable object going to collide with irresistable force (which is always a hard problem).

We had that one cycle with Alex where some of the models got things on the wrong side.

Yah, I see what you are saying, but we are almost to the critical juncture and even a moron like myself can see the setup for the next 24 hours.
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2939. KEEPEROFTHEGATE (Mod)
011L/MH/I/C4
MARK
17.75N/47.55W
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2938. LBU1
Quoting Flyairbird:
I;ve been asking that ever since someone posted that blob....where can we get a good overhead on that , I forgot which

Link
shttp://www.ssd.noaa.gov/eumet/eatl/loop-wv.htmlatellite


Stop loop on last frame.
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2937. help4u
I see all the south wobble casters out tonight.
Member Since: September 18, 2006 Posts: 0 Comments: 1256
Anyone else concerned(even slightly) that 3 of the 6 models are hinting at a bit more of a westward shift? As opposed to the previous strong consensus re-curving Igor well out to sea.... I am.
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Quoting HurricaneGeek:


Yeah, true. But the thing is there HAS to be a reason why. Those guys at the NHC are no dummies. I just would like to know the reasoning behind the odd number selection for those milestones.

74 makes a Hurricane. Why not 75?
111 makes a major . Why not 110? 115?
156 makes a CAT 5. Why not 155?


All I can say to that is...

The NHC works in mysterious ways...
Member Since: August 19, 2008 Posts: 104 Comments: 503
Quoting philliesrock:
Wobbling WSW.

Link


Hey first place feel good, huh?

Hopefully it's just a wobble!
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And now......For Something Completely Different..............Link
Member Since: August 3, 2005 Posts: 10 Comments: 5458
2931. pottery
Quoting CaneAddict:


Check out satellite imagery...it's CLEARLY heading southward..whether it's a wobble or not. Hopefully just a wobble..

Just looked at that.
The models (post 2906) show a little southward before NW.
So hopefully, just a little something to keep us excited.
I dont really want to be excited right now....
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Quoting KimberlyB:


I know I know the answer to this question, but I cannot remember and it's been driving me crazy today (cause Ive been here all day lol)

What does "EWRC" stand for?


Eye Wall Replacement Cycle
Member Since: Posts: Comments:
2929. angiest
Quoting KimberlyB:


I know I know the answer to this question, but I cannot remember and it's been driving me crazy today (cause Ive been here all day lol)

What does "EWRC" stand for?


EyeWall Replacement Cycle
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting nyhurricaneboy:


Technically, you are right.

It's all about the estimates, unfortunately. 110 is a Cat 2, while 111 gets rounded to 115 (Cat 3). Same with 115 being a Cat 4, 156 getting rounded to 160 (Cat 5).

Honestly, I think that your solution is feasible. There really isn't much difference between a 110/"115" or 155/"160" mph storm when it comes to damage.

Now, let's try telling that to the NHC. ;)


Yeah, true. But the thing is there HAS to be a reason why. Those guys at the NHC are no dummies. I just would like to know the reasoning behind the odd number selection for those milestones.

74 makes a Hurricane. Why not 75?
111 makes a major . Why not 110? 115?
156 makes a CAT 5. Why not 155?
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Quoting pottery:

True!
What's this I hear about a SW jog in the track?


I do not see that....maybe just a hair but we have a massive storm....you know how the room reacts to each Wobble
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recon has found some west winds in the recon of 92l
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Wobbling WSW.

Link
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2924. will40
Quoting Flyairbird:
I;ve been asking that ever since someone posted that blob....where can we get a good overhead on that , I forgot which satellite


Link
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Quoting RecordSeason:
2896:

Well, it can't have an EWRC without an outer eye-wall, and it doesn't have an outer eye-wall.


I know I know the answer to this question, but I cannot remember and it's been driving me crazy today (cause Ive been here all day lol)

What does "EWRC" stand for?
Member Since: Posts: Comments:
Quoting angiest:


Looks like he could make it to 65-70W easily without gaining a lot of latitude if that pattern were to hold.


I almost want to put a minus by what you are saying because I live in Puerto Rico and that is the last thing that I want to read. LOL I am watching the storm closely though. If it does not gain latitude we are going to get a direct hit. Not a pretty thought.
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Quoting RecordSeason:
2896:

Well, it can't have an EWRC without an outer eye-wall, and it doesn't have an outer eye-wall.


I know dude, i'm just picking on ya ;p. goodnight all.
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NOGAPS, HWRF AND GFDL all show it curving back to the west. Is this a high building in?
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Julia weakening?
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 13 SEP 2010 Time : 011500 UTC
Lat : 13:29:39 N Lon : 23:36:36 W


CI# /Pressure/ Vmax
3.2 / 997.6mb/ 49.0kt


Final T# Adj T# Raw T#
3.1 3.2 3.2

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -60.8C Cloud Region Temp : -48.7C

Scene Type : IRREGULAR CDO

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF
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Quoting LBU1:


That blob is huge.
I;ve been asking that ever since someone posted that blob....where can we get a good overhead on that , I forgot which satellite
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Quoting HurricaneGeek:
I have never understood why, if 111 is the threshold for a cat 3, why the the NHC never says a storm is 11 mph. They go right from 110 to 115.
Wouldn't it be easier to make a 110 storm a CAT 3 and a 155 storm a CAT 5?
1 mile per hour, does it really make any difference at all?


Technically, you are right.

It's all about the estimates, unfortunately. 110 is a Cat 2, while 111 gets rounded to 115 (Cat 3). Same with 155 being a Cat 4, 156 getting rounded to 160 (Cat 5).

Honestly, I think that your solution is feasible. There really isn't much difference between a 110/"115" or 155/"160" mph storm when it comes to damage.

Now, let's try telling that to the NHC. ;)
Member Since: August 19, 2008 Posts: 104 Comments: 503
Quoting dracko19:
OMG! The NOGAPS just shifted. Its heading directly at....um....well...

What kind of wobble was that?
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2914. mbjjm
Quoting dracko19:
OMG! The NOGAPS just shifted. Its heading directly at....um....well...



Remember the Nogaps with Earl, had over the NE Us
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I know...eating nachos with peppers watching my Boys choke...it won't be pretty...
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Quoting pottery:

True!
What's this I hear about a SW jog in the track?


Check out satellite imagery...it's CLEARLY heading southward..whether it's a wobble or not. Hopefully just a wobble..
Member Since: Posts: Comments:
That is forecasted to move east.....

Quoting will40:



also notice that bigg high over the GOM
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2910. angiest
Quoting btwntx08:
00z bam suite have shift northward in a big way


As of now, they probably still have the best feel for this system. Once we get a closed circulation I'll pay more attention to the other models.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
2909. will40
Quoting Goldenblack:
Wow, just don't see the trough influencing steering at this time, maybe the second trough, but I am now seeing what StormW was talking about.




also notice that bigg high over the GOM
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2908. LBU1
Quoting Vero1:
The Blob over Africa



That blob is huge.
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2907. KEEPEROFTHEGATE (Mod)
........MODEL UPDATE........
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OMG! The NOGAPS just shifted. Its heading directly at....um....well...

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Quoting HurricaneGeek:
Although barley, 60W and south of 20N is STILL in the NHC's 5p m cone.

LINK


Well if they have as much error as they did with Earl...i'd bet on a SE U.S. landfall.
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I have never understood why, if 111 is the threshold for a cat 3, why the the NHC never says a storm is 11 mph. They go right from 110 to 115.
Wouldn't it be easier to make a 110 storm a CAT 3 and a 155 storm a CAT 5?
1 mile per hour, does it really make any difference at all?
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2902. pottery
Quoting traumaboyy:


No Fun....glad to laugh about it now though!!

True!
What's this I hear about a SW jog in the track?
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2901. Vero1
The Blob over Africa

Member Since: July 21, 2008 Posts: 4 Comments: 2233
Oracle....that won't last long...but thanks for the laugh. I'm gonna' have to watch that whole movie again, soon.
Member Since: August 3, 2005 Posts: 10 Comments: 5458
2899. angiest
.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
2898. angiest
Quoting Goldenblack:
Wow, just don't see the trough influencing steering at this time, maybe the second trough, but I am now seeing what StormW was talking about.



Looks like he could make it to 65-70W easily without gaining a lot of latitude if that pattern were to hold.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting RecordSeason:
2878:

Nah, based on microwave and Shortwave IR, Igor isn't even close to thinking about IWRC...


So now the hurricane sends you private messages and last message from Igor said, "yeah, ima wait, i don't feel like shutting my eye right now, i'll let you know when I plan on doing so."
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.