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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Super 93L....
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We will NEVER Forget, and through it all the fools have fallen, there she STANDS!

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Quoting Drakoen:


I'm actually wondering why they don't just go ahead and classify 93L already.


We'll see why in less than 20-30 minutes...
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting Drakoen:


I'm actually wondering why they don't just go ahead and classify 93L already.


Yeah, I don't see why it's not a tropical cyclone already. The NHC has to have their steps of classification though. They can't upgrade a disturbance to a tropical cyclone without coloring it red first. Lol.
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Can you see that ugly face, with his mouth open????
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Quoting Drakoen:


I'm actually wondering why they don't just go ahead and classify 93L already.
i am thinking at 5Pm ,all observations support TD status, and is much better organized than 92L
Member Since: July 14, 2009 Posts: 0 Comments: 3029
Quoting MississippiWx:


Yep, we seem to agree on 92L. I like its chances for development, but it's still 12 hours or so from being where it needs to be.


I'm actually wondering why they don't just go ahead and classify 93L already.
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MississippiWx that Ascat pass was from this morning so the Ascat missed the COC and the rest of it but the new one that come in could show diffrently
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http://www.ssd.noaa.gov/goes/flt/t2/vis-l.jpg

Coquis are singing that means Mucha Agua!
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Quoting Drakoen:


It caught the western most side. Also, current surface observation s do not support a closed low. It looks to be all in the mid levels. 93L has a much better defined low level center.


Yep, we seem to agree on 92L. I like its chances for development, but it's still 12 hours or more from being where it needs to be.
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I think that 92L's percentages will increase at 2 PM but not become a TC. At 5 PM is when think that TD 12 will be born.
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Quoting btwntx08:
i would look at radar to double check also well know something in 30 minutes
Don't need radar to show me anything. It definitely does not have a defined closed low level circulation.
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Quoting btwntx08:
ascat didnt pick up 92L so we dont know


It caught the western most side. Also, current surface observation s do not support a closed low. It looks to be all in the mid levels. 93L has a much better defined low level center.
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Quoting btwntx08:
ascat didnt pick up 92L so we dont know


It shows plenty of the western part of 92L to tell there are no west wind components with it.
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Quoting jonelu:


Its is really big. Boy I hope Haiti can avoid the rain...because all those earthquake refugees have enough to worry about.


here in san juan is raining a lot more heavy than Earl
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SAL is minimal for all three systems- looks like Igor cleared a moist path for 93L.

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Quoting luigi18:


well here is raining a lot san juan area

Convection heading toward PR. A lot of rain here in Toa Alta already.
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Quoting Drakoen:
ASCAT pass already showing up some 30-35 knot wind vectors on 93L:



So far, most of 92L seems to be mid-level. Low clouds on visible don't seem to be indicating a closed low level center and I don't believe it will be classified today. It looks nice, but it also looks just like that disturbance that formed off of the Yucatan last month that was all mid-level. I will say that 92L has a good bit more 850mb vort than the disturbance I'm referring to had. I think 92L will become a TC, just not sure about today.
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Quoting btwntx08:
sterring suggests that 92L wont go over pr or north of there


Not like I don't believe you, but could you provide a source? I'm looking at CIMSS and I can't find it.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting moonlightcowboy:
E D I T


Good morning, all.

RESPECTS remembering the 911 fallen and their families!




Igor is going to struggle with dry air just as the others have before it, keeping the system disrupted but not enough to TO NOT feel the tug of the approaching trough. 92L is in the dead zone, hardling anything spins up there - at least not quickly. It's a broad system and, like xG, will have a tough time getting wound up tight around a coc. 93L, however, looks fairly impressive early, but they all do in that position.

It's a waiting game, and I'm beginning to wonder if prevailing conditions can be too perfect? SST's too warm for development? Certainly, much has defied development odds so far, imo.

that is so beautiful! god bless the fallen and their families, and our troops and their families always. and god bless America!
i hope 92l don't come our way and i am hoping that Igor goes out to sea. does anyone think that 92l will affect the gulf coast? and what is the thinking for Igor? thanks in advance
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No indication of a surface circulation on 92L:
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ASCAT pass already showing up some 30-35 knot wind vectors on 93L:

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Quoting KanKunKid:


Um, then what are you doing? I was attacking the phraseology, not a person.

That was a defense from your use of "drama, annoying and exageration " words. And a defense of my phraseology.

explosion (etymology)
1620s, "action of driving out with violence and noise," from Fr. explosion, from L. explosionem (nom. explosio), noun of action from pp. stem of explodere "drive out by clapping" (see explode for origin and sense evolution). Meaning "going off with violence and noise" is from 1660s. Sense of "rapid increase or development" is first attested 1953.
http://www.etymonline.com/index.php?term=explosion

Now you are going to admit that you meddling with a wrong argument and using offensive wording? Or I need to expect more excuses.

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Quoting btwntx08:


Vorticy is incredibly good with Igor, decent, in 92L.
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Quoting 7544:
92 is lifting north going over pr ?


well here is raining a lot san juan area
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Quoting btwntx08:
my thoughts for the incoming two
92L=70-80%
93L=50-60%


Seem reasonable legittimate predictions, as we're thinking in the minds of the NHC, keep in mind... ;)
Member Since: April 1, 2010 Posts: 9 Comments: 2699
284. 7544
looks like 92l is trying to follow the hwrf path hmmmmm all the conv to the north and could reform there imo
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Hello?
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Igor appears to be getting smaller- a sign of a system tightening up. I expect a hurricane at 5 PM, and a Tropical Depression, plus Code Red for 93L.
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Quoting Seflhurricane:
92L will more than likely be upgraded at 5pm, my main concern will be the heavy rain on the islands it is a huge storm


Its is really big. Boy I hope Haiti can avoid the rain...because all those earthquake refugees have enough to worry about.
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I'm back...
Member Since: April 1, 2010 Posts: 9 Comments: 2699
For all you who are just following the convection, the center of 92L is south of the strongest convection...

Quoting 7544:
92 is lifting north going over pr ?
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Good afternoon...

NAM has been doing a pretty good job with the moisture fields and propagation for 92L.
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Quoting beell:
Hey, Drak,
Good time to get on the list of well-wishers as you begin your formal education.

If you can survive on the Doc's blog-you can make it anywhere.

Good Luck!

And Levi, too!


Thank You!
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Quoting Drakoen:


TS or Hurr conditions
hey drak good to hear from you, so far florida has been spared so far
Member Since: July 14, 2009 Posts: 0 Comments: 3029

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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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