Potentially dangerous 92L steadily developing; Igor nears hurricane strength

By: Dr. Jeff Masters , 3:04 PM GMT on September 11, 2010

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A tropical disturbance (92L) over the Eastern Caribbean, a few hundred miles south of Puerto Rico, is steadily organizing and appears likely to develop into a tropical depression by tonight or Sunday morning. Satellite loops show an impressive and expanding region of heavy thunderstorms, with good spiral banding and respectable upper-level outflow on all sides. Long range radar out of Puerto Rico shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. However, the rain bands are becoming more intense and more organized. San Juan, Puerto Rico reported a heavy rain squall at 8:44 am this morning, and radar estimates suggest two inches of rain fell in this squall just southeast of San Juan. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are at near-record warmth, 30°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-northwest at 11 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 Mexico's Yucatan Peninsula on Wednesday. The HWRF model has a more northwesterly track, taking 92L over the Dominican Republic, Haiti, and Cuba, but this model has been trending too far north in its tracks. I expect 92L will follow a path south of the islands, bringing it near or just south of Jamaica on Monday, then into the Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches tonight through Monday morning; southern Haiti can expect similar rains Sunday through Monday, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba will probably escape 92L's heaviest rains in this scenario (Figure 2.)

Intensity forecast for 92L
I can't find any reason to doubt this will be a tropical storm by Sunday or Monday, and potentially a Category 1 or 2 hurricane by Wednesday, if 92L avoids passage over Hispaniola and Cuba. The SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and makes 92L a Category 1 hurricane by Monday night. 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. The first Air Force Hurricane Hunter mission into 92L is scheduled for Sunday afternoon, but there will be a research mission by the National Center for Atmospheric Research G-V jet today that will give us valuable information on 92L's large scale environment and potential for development.


Figure 2. Forecast rain amounts from 92L from the 2am EDT Saturday run of the GFDL model. This model predicts most of 92L's heaviest rains will miss Haiti, but will affect Jamaica, the Cayman Islands, and the Yucatan Peninsula. Image credit: Morris Bender, NOAA/GFDL.

Igor
Tropical Storm Igor is very close to hurricane strength, and appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is moderate, 15 - 20 knots, waters are warm, 28°C, and Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor will track west under the influence of a strong ridge of high pressure for the next three days, then turn more to the west-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 has a slight chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 10% 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 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model 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. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.

Elsewhere in the tropics
A new tropical wave (Invest 93L) emerged from the coast of Africa yesterday, and is already showing signs of organization. Most of the models predict 93L will develop into a tropical depression 2 - 4 days from now, and NHC is giving 93L a 30% chance of developing by Monday.

Next post
This may be my only post today; I'll have a new post Sunday morning.

Jeff Masters

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872. IKE
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Quoting will40:


look at all those lows in Carrib


SmileyCentral.com Do I have to?
Member Since: August 24, 2010 Posts: 0 Comments: 459
Quoting weatherportricheyfl:
has anyone seen the scary model for the gfs 384 hrs from now west coast of florida get ready

Link
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julia karl and igor can really be a part 2 of danielle fiona and earl
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Quoting weatherportricheyfl:
has anyone seen the scary model for the gfs 384 hrs from now west coast of florida get ready


That was on the 0Z but not on 12Z.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
is the af c130 recon flying 92l today?
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Happy B-day to Dr. Masters who is 50 today,,one can send him B-day wishes here..on FACEBOOK.
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has anyone seen the scary model for the gfs 384 hrs from now west coast of florida get ready
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Quoting weatherlover94:


what does this mean? a greater threat to the us?


Nope, this run recurves east of Bermuda.. Though I am trying to explain why the ensembles are not in agreement, along with the EURO ensembles and some other model runs.
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Quoting reedzone:
The second trough is stronger on the new run, this would really strengthen the ridge to the west.


does this make a us hit more likely?
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...really Kman..also your calm during chaos here on the blog hasn't gone unnoticed....thx and now back to my dark shade tree....not a troll..per se....just trolling...lol...is that the same?
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92L may still fire back up tonight.
stay tuned.
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Quoting Seflhurricane:
very true
a flattened trough can be dangerous,a storm will stall and the take a sharp turn left.beware
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Quoting KanKunKid:


Well, I kinda thought Angiest might post it when it is done running. Here is the link for the graphic of the GFS
Link


It dropped 92L.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting reedzone:
The second trough is stronger on the new run, this would really strengthen the ridge to the west.


what does this mean? a greater threat to the us?
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Happy Ivan Anniversary Kman!
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Quoting kmanislander:


LOL. Thanks.


Kman,
Is there a technical name for the John Hope rule?

Trying to google it TIA
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Quoting Legion:
I always wondered why it is that a lot of people praise the John Hope rule but you see so many mocking the Hebert boxes? Paul Hebert was a very knowledgeable meteorologist also, and his boxes are worthy of merit too, the proof is in the pudding.


From what I gather people misunderstand the Hebert Boxes. Whereas the Hope rule predicts behaviour of a storm, the Hebert Box shows where a storm came from.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
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114 hours..


Second trough is strong, straight north of Igor which means Igor has to recurve soon or the ridge, which is also strong builds and steers him west.
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Quoting RecordSeason:
Patrap:

How did you get those?

The dumb SSD site still won't go past 2015 for me on Igor, and won't go past 1945 on 92L...


I know a Lady in Boca who has a connection in NOAA.
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Looks like 92L went poof today.
gotta run. l8r.
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look at all those lows in Carrib
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Patrap, congrads on the Thursday night game.

As far as those photos, that system is doing something. I want to see what will happen once they are able to get favorable conditions to fly their missions into it.
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Quoting Seflhurricane:
so far South Florida has been spared from a hurricane But the bad month for us is October so enjoy while it lasts
Some people who live in South Florida do not even realize that October is a very dangerous month...And more tropical cyclones have hit S.W.Florida in October than in any other month.
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I miss John Hope too!
I remember his first day on TWC.
never missed his updates !
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The second trough is stronger on the new run, this would really strengthen the ridge to the west.
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Everyone in the Northern Leeward islands needs to monitor Igor very closely even though models have it to its Northeast look what happened to Earl and Igor is going to be much much stronger when it makes its closest approach
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92L Rainbow Image





RGB




WV

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Quoting will40:


wandering is wayyyyyyyyyyyyyyy too expensive hee hee


Boy aint that the truth! In more ways than one. I'm getting too old to keep starting over. And my own bed is really comfy at night.SmileyCentral.com
Member Since: August 24, 2010 Posts: 0 Comments: 459
Quoting Txwxchaser:
Kman..you should seriously being teaching a class somewhere...very understandable explanation of what might/might not steer Igor..really appreciate things in layman terms.


LOL. Thanks.
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834. JRRP
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Quoting moonlightcowboy:


Plywood, I've got to look at the basics - there've been so many things said, the models doing whatever and we aren't short on any opinions. I can't see Igor missing the tug of the trough. EC landfall? I'm not thinking so, not at this time, but I guess the chance still remains. As far as 92L - it's a mess, no LLC is clearly evident, scattered convection. It acts like xG who could never get anything going. Still, as it drifts west or wnw I can see the high TCHP values giving it the extra spark it may need to get churning. As far as track then, I'd think he'd ride more northwards on the western periphery of the high weakened by the wake of the trough and the departing Igor. And, who knows really - the ridge may build back in and it may track further west. It's got to develop first - not real sure about it yet.
Good to see ya around, MLC.
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The trough is weaker on the 18Z, the first one that is.. Also going a few more frames, the high is a tad stronger.
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Kman..you should seriously being teaching a class somewhere...very understandable explanation of what might/might not steer Igor..really appreciate things in layman terms.
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Quoting PensacolaDoug:
The "John Hope" rule (god I miss that guy) is showing its power today.


No question about that. Whenever I see a weak system pass 63 W without closing off I say thanks to John for his great knowledge and grasp of all things tropical.
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Quoting KanKunKid:


The answer is in the models, or guess. It is of significance because the models weren't developing it before. Now, if they are, there has to be a reason, and it doesn't look like circulation. We should see a plot soon, that may answer your question(s)and my musings.


Hey Kid, could you post that model or tell me how to find it...Corpu here and want to keep ahead of the game on this one 92L, we have been lucky so far...
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so far South Florida has been spared from a hurricane But the bad month for us is October so enjoy while it lasts
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Quoting plywoodstatenative:
what did NOAA find with their plane today, any idea?
They finally found the ocean...
(sry)
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Quoting kmanislander:


Take a look at this WV loop

You will see two troughs. The first is now off the East coast and will reinforce the ridge behind it. Igor will not be caught by the first trough.

The second trough can be seen pushing through the Great lakes area now. That is supposed to dig down and pick up Igor. If that second trough is flat and does not amplify it will only pull Igor up to the WNW and NW for a time but may not effect a recurve. Behind that trough another ridge will then build back in which could force Igor back towards the West and WNW.

As usual it is all about timing and strength of the various features. Stay tuned.
very true
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Quoting kmanislander:


Take a look at this WV loop

You will see two troughs. The first is now off the East coast and will reinforce the ridge behind it. Igor will not be caught by the first trough.

The second trough can be seen pushing through the Great lakes area now. That is supposed to dig down and pick up Igor. If that second trough is flat and does not amplify it will only pull Igor up to the WNW and NW for a time but may not effect a recurve. Behind that trough another ridge will then build back in which could force Igor back towards the West and WNW.

As usual it is all about timing and strength of the various features. Stay tuned.


Earl came down to timing, and it was quite tight....
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting kmanislander:
Great ventilation courtesy of high pressure aloft



But next to nothing going on at the surface



Until we see some convergence at the surface 92L will not develop a closed low

I guess we'll see what happens later tonight.
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Quoting joetuttledays:
Thank you aall so much for the welcome. Let me just jump right in. This is only an opinion, from what I see I dont believe the Low's coming off the east coast of the US will dig far enough south to recurve Igor. What I think will happen they will have enough of an influence to lift Igor to the NW but I just dont see the recurve. What feedback-if any?


Take a look at this WV loop

You will see two troughs. The first is now off the East coast and will reinforce the ridge behind it. Igor will not be caught by the first trough.

The second trough can be seen pushing through the Great lakes area now. That is supposed to dig down and pick up Igor. If that second trough is flat and does not amplify it will only pull Igor up to the WNW and NW for a time but may not effect a recurve. Behind that trough another ridge will then build back in which could force Igor back towards the West and WNW.

As usual it is all about timing and strength of the various features. Stay tuned.
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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.