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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1746. leo305
Quoting Max1023:


Igor is not undergoing RI anymore winds wise, the organization suggests about 10 knots per 6 hours of strengthening. To me RI starts at 15. For a hurricane of Igor's strength though intensification after Category 4 is rare.

Pressure wise Igor is probably deepening at about 2-3mb an hour, near the line. At the rate it's going it would be a Cat 5 by 5am, however I doubt that Igor will continue to strengthen that far this early. The water temps do not support it.


I don't think the water is the main issue, I think the upper air conditions wont allow it
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1745. angiest
Quoting JLPR2:
There is just no end in sight.



I wonder if the Caribbean storm GFS has been developing in two weeks is in the picture yet.
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Quoting scott39:
Why is anybody debating the track of Igor past 72 hours?


because :)
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Quoting MiamiHurricanes09:
It probably could be. We'll just have to see for how long it intensifies rapidly. Right now, cloud tops are cooling and the eye is becoming better defined. If cloud tops begin to warm, then the stage of rapid intensification will likely be over and he'll likely maintain intensity until he weakens due to an EWRC.

Hopefully, he'll reach Cat5 status for 2 advisories or so and gradually weaken by the time he reaches any landmass.
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1740. Vero1
Quoting will40:
.UKMET AND ECMWF REMAIN TO THE LEFT OF THE CONSENSUS AND ARE
SLIGHTLY SLOWER...WHILE THE OTHER REGIONAL AND GLOBAL MODELS
SUGGEST A MORE PRONOUNCED WEAKNESS WITH TIME IN THE MID- TO
UPPER-LEVEL RIDGE.


.BUT STILL TO THE LEFT OUT OF RESPECT TO THE RELIABLE ECMWF
MODEL.

thats the two worrying parts of the discussion to me


confusing?
Member Since: July 21, 2008 Posts: 4 Comments: 2233
1739. JLPR2
There is just no end in sight.

Member Since: September 4, 2007 Posts: 7 Comments: 8732
Quoting angiest:


With a pinhead eye!

we all doom!
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1736. IKE
Quoting doorman79:


You aren't poking your chest out like a bannie rooster are ya? lol joke


Nope...not me. Man has to know his limitations.
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The trough that is supposed to encounter Igor extends down to 23N. Igor outer bands extend to 21 N. If that trough doesn't moves more to the south, maybe to 20N, there's a probability that it will miss Igor, and it will keep its westerly track. So We should be observing Igor, here in PR.
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1734. angiest
Quoting DestinJeff:


or annular??????


With a pinhead eye!
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1733. Max1023
Quoting WeatherNerdPR:

Wait a minute...If a moderate Cat4 is undergoing RI, shouldn't it be a Cat5 by 11?


Igor is not undergoing RI anymore winds wise, the organization suggests about 10 knots per 6 hours of strengthening. To me RI starts at 15. For a hurricane of Igor's strength though intensification after Category 4 is rare.

Pressure wise Igor is probably deepening at about 2-3mb an hour, near the line. At the rate it's going it would be a Cat 5 by 5am, however I doubt that Igor will continue to strengthen that far this early. The water temps do not support it.
Member Since: July 22, 2008 Posts: 1 Comments: 286
1731. scott39
Why is anybody debating the track of Igor past 72 hours?
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Quoting IKE:


Thanks for the compliment!


You aren't poking your chest out like a bannie rooster are ya? lol joke
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Quoting WeatherNerdPR:

Wait a minute...If a moderate Cat4 is undergoing RI, shouldn't it be a Cat5 by 11?
It probably could be. We'll just have to see for how long it intensifies rapidly. Right now, cloud tops are cooling and the eye is becoming better defined. If cloud tops begin to warm, then the stage of rapid intensification will likely be over and he'll likely maintain intensity until he weakens due to an EWRC.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1727. IKE
Quoting scott39:
Ike, what are the tracks for storms, that form where 92L is, this time of year?


Clips(CLP5), model could tell you.....Link

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Quoting Hurricanes101:


Exactly, it would be nice if some would follow the lead of people like Drak, Levi, StormW and Kman. They don't always agree, but when they disagree with each other they do it the right way.
yes but the difference is, to me anyway, that everyone on that list knows what they are talking about, unlike a lot of people here who wishcast
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Is Igor gonna be a cat 5??
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1724. angiest
This is what 18Z GFS is initializing on:

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Thanks folks
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Quoting CaptnDan142:


I mostly lurk, and I have certainly seen the same thing. But, it isn't limited to west-casting. You pretty much get attacked around here no matter what. Calling it a fish storm is as big a sin as saying it'll slam Florida. And whatever you do, don't ever suggest something may dissipate. Then you're a down-caster.

One thing I have noticed though... I don't ever recall any of the 'attackers' coming back after the fact and pointing out that someone ended up being right. I guess it just doesn't work that way around here.

All that aside, there is some useful info to be had here. You just have to do a lot of tuning-out and sorting through the garbage.

Lurking isn't a bad way to go.



You forgot about mentioning the trials of downcasters.
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1720. angiest
Quoting PcolaDan:


Unfortunately it is becoming a forum of "I'm right and you're wrong and if you disagree you're an idiot."


And never suggest the possibility of landfall, or that people should be prepared for it.
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1719. scott39
Quoting IKE:


Thanks for the compliment!
Your Welcome
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Quoting PcolaDan:


Unfortunately it is becoming a forum of "I'm right and you're wrong and if you disagree you're an idiot."


Exactly, it would be nice if some would follow the lead of people like Drak, Levi, StormW and Kman. They don't always agree, but when they disagree with each other they do it the right way.
Member Since: March 10, 2010 Posts: 1 Comments: 7813
Quoting MiamiHurricanes09:
Pretty easy to see why the RAW T# are increasing so quickly. Notice the very intense ring of strong strong thunderstorm activity that has developed around Igor's inner core/eye.

Based on this, Igor continues to undergo rapid intensification.

Category 4 Igor Satellite Loop


Wait a minute...If a moderate Cat4 is undergoing RI, shouldn't it be a Cat5 by 11?
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1716. scott39
Ike, what are the tracks for storms, that form where 92L is, this time of year?
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Quoting reedzone:
Before I leave...

Some of you are really immature, MSK was just stating his opinion that Igor could recurve a little too late, which is entirely a possible situation. It's not a guarantee that Igor will miss the USA, cut it out now! Let people share their opinions, it's a forum.


Unfortunately it is becoming a forum of "I'm right and you're wrong and if you disagree you're an idiot."
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1714. Max1023
Quoting MiamiHurricanes09:
Pretty easy to see why the RAW T# are increasing so quickly. Notice the very intense ring of very strong thunderstorm activity that has developed around Igor's core.

Based on this, Igor continues to undergo rapid intensification.

Category 4 Igor Satellite Loop


The eyewall is cooling about 1 degree an hour on average and the eye is warming about the same right now. This has to stop soon though, as Igor can only get so strong over 28 degree water. If upper level conditions remain nearly perfect like they are now then Igor should very slowly strengthen as the waters underneath warm, then begin to slowly decay once he crosses 25 North.

I think the magic Number is +20/-75, if ADT records that then we have a cat 5.
Member Since: July 22, 2008 Posts: 1 Comments: 286
1713. will40
Quoting Herbertsbox:
Right now the NHC has Igor starting its curve at about 51.5 west. Curious to see when and where it does. I assume it has been missing the forecast point up until now...yes?


nope been mostly right on the points today
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1712. leo305
Quoting btwntx08:
i believe that is happening leo could be a relocation under that developing convection will see though in the next few hrs


yep, the anticylone is centered right over it too, perfect conditions for rapid development
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1710. IKE
Quoting scott39:
LOL, Thank God for Ike!!


Thanks for the compliment!
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Quoting IKE:


Good. Thanks for posting that. I'll be looking out for their reports. Looks a little encouraging for you...so far, based on satellite, to me.
Sure hope so although Dolly never "developed" a closed circulation until she passed us and we had very strong TS winds and flooding rains. Looks like the rain from this will pass right over us but not sure.
Member Since: October 9, 2008 Posts: 0 Comments: 8391
1707. angiest
Quoting Herbertsbox:
Right now the NHC has Igor starting its curve at about 51.5 west. Curious to see when and where it does. I assume it has been missing the forecast point up until now...yes?


He is still on line from the forecast three days ago.
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1706. scott39
Quoting DestinJeff:


No, but it is our luck that Ike lives here. The Downcasting Energy around this area is so extreme that no storm dare come near here.

Ike, The Storm Whisperer.
LOL, Thank God for Ike!!
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1705. IKE
Quoting DestinJeff:


No, but it is our luck that Ike lives here. The Downcasting Energy around this area is so extreme that no storm dare come near here.

Ike, The Storm Whisperer.


LOL.

Amen. I'm counting the Opal days(Oct. 4th).
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Right now the NHC has Igor starting its curve at about 51.5 west. Curious to see when and where it does. I assume it has been missing the forecast point up until now...yes?
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Pretty easy to see why the RAW T# are increasing so quickly. Notice the very intense ring of strong thunderstorm activity that has developed around Igor's inner core/eye.

Based on this, Igor continues to undergo rapid intensification.

Category 4 Igor Satellite Loop

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting PcolaDan:


An ambiguous term at best and, obviously, highly debatable. My opinion? Any storm that has no detrimental affect on any land, i.e. severe erosion, flooding, etc., and of course the obvious. Others have differing opinions I'm sure.


I would think its more of an amphibious term lol
Member Since: March 10, 2010 Posts: 1 Comments: 7813
1700. leo305
I believe 92L will become a Depression or tropical storm tonight.. rather quickly.. the environment is perfect for it to become a tropical cyclone.. and on visible a LLC is forming under that deep convection near 17N
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1698. angiest
Quoting DestinJeff:


No, but it is our luck that Ike lives here. The Downcasting Energy around this area is so extreme that no storm dare come near here.

Ike, The Storm Whisperer.


LOL
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1697. Max1023
Igor could theoretically go anywhere from east of bermuda to the OBX. At the range we are talking (7 days plus) almost anything can happen. A CONUS landfall seems unlikely however it is not impossible, a Bermuda strike seems more likely, however both are too far in the future for a reliable forecast. Anyone living within 1000 miles of 26 degree water within 200 miles of the coast should always be ready for a hurricane with a plan in place, as storms like these are extremely dangerous and hard to forecast more than a few days out. Igor may be a fish storm from now on (notwithstanding it's CV hit) however always prepare for the worst. Hope for the best, but be ready.
Member Since: July 22, 2008 Posts: 1 Comments: 286
Quoting tinkahbell:
What exactly constitutes a "fish storm"? I would think that if it affects land in any way it could not be termed a "fish"...right? Wrong?


An ambiguous term at best and, obviously, highly debatable. My opinion? Any storm that has no detrimental affect on any land, i.e. severe erosion, flooding, etc., and of course the obvious. Others have differing opinions I'm sure.
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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.