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 Levi32:
Igor has begun a WSW jog during the last couple hours after being on a due west heading. Just a jog but worth pointing out as it may take Igor south of the next forecast point.
someone said earlier that you thought this trough had a chance to miss it and the high to build back in and send this toward florida and the SE coast.

1) is this true
2) what chance do you have of this happening
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Couple of hours old, but...

WOW

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Quoting BDAwx:


funny thing is our authorities haven't made any public statements about this... except for the Bermuda Weather service who says "See latest Tropical Update Bulletins for Hurricane Igor updates." and links you to here
They are probably waiting for at least another 48 hours. I-man is still way out in the atlantic.
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Quoting LongIslandXpress38:


Thankfully Igor is going to recurve!


That isn't certain. Likely, but not certain.
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Quoting JLPR2:
Some slight reflection in the 850mb level with the wave inland.



What is that system near Spain?
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Quoting MiamiHurricanes09:

Dealing with that dry air quite well.
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2590. Seastep
Quoting Krycek1984:
And how can Igor be so strong and well organized when it's ramming right into all that dry air?


None of that really matters for a storm of this strength. Has minimal effect.
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Quoting LightningCharmer:
If I've been informed correctly, Bermuda has some of the strictest building codes in the world. Even so, Igor cannot be taken lightly in my humble opinion.


Thankfully Igor is going to recurve!
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
2587. Drakoen
Quoting Stormchaser2007:
Now we are up to 10 storms.

Quite a bit of time left for 7-9 more storms.

Specially if this active period continues through October.


Yup. I would put it at 7-10 more named storms possible.
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Quoting DESteve:
StormW sharing his comments with BarometerBob @ irc.hurricanehollow.org


Thanks! :)
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Quoting Levi32:
Igor has begun a WSW jog during the last couple hours after being on a due west heading. Just a jog but worth pointing out as it may take Igor south of the next forecast point.


The flow in front of Igor has not changed yet either.
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Quoting hurristat:


It was the only TD that formed over Africa to be named... there were several that formed but were not named.

Ah, thanks for that. I didn't know that. Do you have a link or anything so I can see some of them? TIA
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Quoting JLPR2:
Don't you just hate it when ASCAT misses. :|



Doesn't it always?
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If I've been informed correctly, Bermuda has some of the strictest building codes in the world. Even so, Igor cannot be taken lightly in my humble opinion.
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2581. BDAwx
Quoting Flyairbird:
If I were you ,I would just check this from time to time and listen to your authorities.....


funny thing is our authorities haven't made any public statements about this... except for the Bermuda Weather service who says "See latest Tropical Update Bulletins for Hurricane Igor updates." and links you to here
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TAFB also at T6.5.

TAFB, SS, I, 1, 6565 /////, , , MET8, CSC, T, DT = 6.5 BASED ON IR EYE PATTERN. NLINEEYE COLOR==
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Quoting JLPR2:
Don't you just hate it when ASCAT misses. :|



They have been playing horse shoes all year...lol
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Now we are up to 10 storms.

Quite a bit of time left for 7-9 more storms.

Specially if this active period continues through October.
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2577. Levi32
Igor will likely be the single greatest ACE contributer to the 2010 Atlantic hurricane season.
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Quoting Levi32:
Igor has begun a WSW jog during the last couple hours after being on a due west heading. Just a jog but worth pointing out as it may take Igor south of the next forecast point.
Levi, How far ?
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Quoting CybrTeddy:
Great Scott!
11, 2010091300, , BEST, 0, 177N, 473W, 130, 935, HU

150 mph, 935 mb.

Dang! Igor getting really close to category 5 strength.
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.
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Quoting AWeatherLover:
The wave behind TD12 looks pretty vigorous this evening. It's looked pretty impressive all day. Reminds me of TS Christina (1972 I believe, but I could be off). It was designated a TD while still over Africa. The only one to do so if I remember correctly.


It was the only TD that formed over Africa to be named... there were several that formed but were not named.
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2572. Drakoen
Water vapor imagery show the eye has completely clear out with the system firing the most intense cloud tops in the southeast quadrant.
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18z's GFDL and HWRF develop 92L


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2570. JLPR2
Don't you just hate it when ASCAT misses. :|

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2010SEP12 234500 6.7 931.4/ +2.0 /132.2 6.7 6.9 6.9 NO LIMIT OFF OFF 16.04 -71.61 EYE 24 IR 17.67 47.10 COMBO
2010SEP13 001500 6.7 931.4/ +2.0 /132.2 6.7 6.8 6.8 NO LIMIT OFF OFF 16.84 -70.02 EYE 24 IR 17.57 47.31 COMBO WSW movement...

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2567. Levi32
Igor has begun a WSW jog during the last couple hours after being on a due west heading. Just a jog but worth pointing out as it may take Igor south of the next forecast point.
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Quoting weatherwatcher12:

Well, I don't think it counts as completely close unless we have true west winds. Correct me if I'm wrong.


I doubt it has a closed circulation...the NHC states "...may not have a well-defined center of circulation"...who knows though.
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Quoting Krycek1984:


How can it reach Cat 5 that far north with all the upwelling of cool water from Danielle?


Danielle was a long time ago.. *shrug*
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WOW.

12/2345 UTC 17.6N 47.2W T6.5/6.5 IGOR
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Stormchaser2007:






+1
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2562. JLPR2
Some slight reflection in the 850mb level with the wave inland.

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Quoting Stormchaser2007:


NHC FTP site


AL, 11, 2010091300, , BEST, 0, 177N, 473W, 130, 935,
I wouldn't be surprised if its higher by the way that the satellite estimates are increasing.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting stormwatcherCI:
What does this mean ? Does it have a closed circulation ?
They'll probly make another pass then we will know for sure but i think it has
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2558. dmaddox
Quoting RecordSeason:
2506:

Igor is not weakening currently.


Given both the Sea Surface Temperatures and the depth of the hot water ahead of Igor only becomes more favourable for at least the next 3 or 4 days, and given the atmospheric conditions are actually BETTER ahead of him for tomorrow and the next day, there is no reason to expect Igor to do any significant weaking any time soon.

It may experience some minor fluctuations, but every available tool suggests Igor is probably going to be at least a mid-level cat5 at some point.


Just my oppinion:

Igor probably will have a "mini-peak" in intensity over night tonight as a cat 5 in the 160mph to 165mph range. Then it may weaken slightly. Then it will reach an even higher peak between 57W and 60W, and probably be near 180mph storm.
WOW!!! they better have a Hunter in there to verify that then!! amazing!
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Quoting Stormchaser2007:




LMAO
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Quoting Stormchaser2007:
Igor was 75 mph at 11pm yesterday.

Now it will be 150mph.

Amazing.
Imagine if we had a landfalling storm that did that in the 24 hours before landfall. How can you forecast something of that magnitude to happen? The impact would be catastrophic.
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2554. bassis
Be back for the 11:00, gonna watch some football
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Quoting Vero1:


A 1007 MB SURFACE LOW S OF HAITI NEAR
16N72W
Good find. Watching the SSD watervapor currently, early outflow seems to be there as well to my untrained eye.
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Quoting dmaddox:
officially? by whom?


NHC FTP site


AL, 11, 2010091300, , BEST, 0, 177N, 473W, 130, 935,
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Quoting BDADUDE:
You guys are actually starting to make me think that we Bermudians actually have something to worry about.
If I were you ,I would just check this from time to time and listen to your authorities.....
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Winds down 5kt.

AL, 92, 2010091300, , BEST, 0, 159N, 733W, 20, 1007, DB,
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Quoting stormwatcherCI:
What does this mean ? Does it have a closed circulation ?

Well, I don't think it counts as completely close unless we have true west winds. Correct me if I'm wrong.
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2547. dmaddox
Quoting Stormchaser2007:


150 mph officially.

Wow.
officially? by whom?
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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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