Igor turns west-northwest; Julia a hurricane; 92L growing more organized

By: Dr. Jeff Masters , 1:49 PM GMT on September 14, 2010

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Hurricane Igor remains an impressive Category 4 hurricane with 135 mph winds over the Central Atlantic. Though Igor's winds are 15 mph weaker than at its 150 mph peak yesterday, the hurricane continues to maintain the classic appearance of a major hurricane on satellite imagery, with a well-formed eye, plenty of low-level spiral bands, and solid upper-level outflow to the north and south.


Figure 1. Hurricane Igor as seen by the MODIS instrument on NASA's Aqua satellite at 12:40 pm EDT Monday, September 13, 2010. Image credit: NASA.

Intensity forecast for Igor
Wind shear is low, 5 - 10 knots, and is expected to remain low for the next 3 - 4 days. Waters are warm, 28.7°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. These conditions should allow Igor to remain at major hurricane status for the next 3 - 4 days. The hurricane will probably undergo one of the usual eyewall replacement cycles intense hurricanes commonly have, where the eyewall collapses and a new eyewall forms from an outer spiral band. This will weaken the hurricane by 10 - 20 mph when it occurs, and may be responsible for the 15 mph weakening Igor experienced since yesterday. Igor will probably regain its lost intensity when the cycle completes in the 12 - 36 hours. By Saturday, when Igor should be nearing Bermuda, the trough of low pressure steering Igor northwestwards should bring moderate wind shear of 10 - 20 knots to the storm, weakening it. Igor will also be tracking over cooler 28°C waters then.

Track forecast for Igor
The track forecast for Igor remains unchanged. Igor has made its long-anticipated turn to the west-northwest, in response to the steering influence of a broad trough of low pressure moving across the Western Atlantic. This trough will steer Igor several hundred miles to the northeast of the Lesser Antilles, and high waves should be the only impact of Igor on the islands. In the longer range, Igor appears likely to be a threat to Bermuda, and that island can expect tropical storm force winds as early as Friday. Igor does have a small chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 20% 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 5 - 10% for Bermuda and 15% for Canada. The forecast steering current pattern for the period 5 - 10 days from now from the ECMWF and GFS models shows several modest troughs of low pressure moving across the Western Atlantic. These troughs will probably be strong enough to recurve Igor out sea. However, 5 - 10 day forecasts are prone to large errors, and it is too early to be highly confident that Igor will miss hitting the U.S. or Canadian coasts.

Wave forecast for Igor
Large swells from Igor have arrived in the Northern Lesser Antilles Islands, and will spread westwards over the next few days, reaching the U.S. East Coast on Friday. By Saturday, much of the East Coast from northern Florida to Cape Cod Massachusetts can expect waves of 3 - 4 meters (10 - 13 feet), causing dangerous rip currents and significant beach erosion. These waves will continue through Sunday then gradually die down. The latest NOAA marine forecast for Cape Hatteras, North Carolina calls for 8 - 11 foot waves on Saturday.


Figure 3. Forecast wave heights for 2pm EDT Saturday September 18, 2010, as predicted by 00 UTC 9/14/2010 run of NOAA's Wavewatch III model.

Caribbean disturbance 92L
Tropical disturbance 92L over the Western Caribbean, between Jamaica and the Yucatan Peninsula, has become more organized this morning. The storm remains a threat to develop into a tropical depression, but time is running out for it to do so. There is no evidence of a surface circulation on satellite loops this morning, but the cloud pattern of 92L has become more circular, with low-level spiral bands developing on the west and north sides of the storm. 92L has a moderate but increasing area of intense thunderstorms; these are bringing heavy rains to Jamaica, the Cayman Islands, and western Cuba this morning.


Figure 3. Morning satellite image of 92L.

Forecast for 92L
Rains from 92L will spread over Belize, Northern Guatemala, and Mexico's Yucatan Peninsula tonight through Wednesday, bringing peak accumulations in the 4 - 8 inch range. Lesser peak amounts of 2 - 4 inches are possible over northern Honduras. Wind shear over 92L is low, 5 - 10 knots, and is expected to remain low for the next five days. The waters beneath are hot, 29.7°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; this dry air has been interfering with development of 92L, and will continue to do so. NHC is putting the odds of 92L developing into a tropical depression by Thursday at 40%; I'll give it a 50% chance. Given the current disorganized state of 92L, it would be difficult for it to intensify quickly enough to become any stronger than a tropical storm with 50 mph winds by Wednesday afternoon, when it will move over Belize and Mexico's Yucatan Peninsula. Once 92L crosses the Yucatan, the ridge of high pressure steering it is expected to remain in place, forcing 92L west or west-southwest to a second landfall in Mexico between Veracruz and Poza Rica early Saturday morning. The shape of Mexico's Bay of Campeche and the topography of the mountains surrounding the Bay help air spiral in a counterclockwise fashion, aiding tropical storm development, and 92L has its best chance of development once it crosses into the Bay of Campeche. With the shear there expected to be low and the waters warm, I give a high 70% chance that 92L will be a tropical depression or tropical storm in the Bay of Campeche. The GFDL model is predicting 92L could be a hurricane at landfall near Veracruz on Saturday morning; the other intensity models are much less aggressive. Given the rapid development of Hermine in a similar location last week, residents of the Mexican Gulf Coast should be wary of the possibility that 92L could intensify into at least a strong tropical storm before making landfall Friday night or Saturday morning. A Hurricane Hunter aircraft is scheduled to investigate 92L this afternoon.

Julia
Hurricane Julia is headed northwest, out to sea, and it is unlikely that this storm will trouble any land areas. The intensification of Julia into a hurricane brings our activity tally for the 2010 Atlantic hurricane season to 10 named storms, 5 hurricanes, and 3 intense hurricanes. An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes, so we've already had a full season's worth of activity, with about 45% of the season still to come.

Shear will be low to moderate, 5 - 20 knots, over Julia during the next two days. Shear will rise sharply to 30 knots 3 - 5 days from now, as Julia moves within 1000 miles of Igor and begins to experience strong northwesterly winds from her big brother's upper level outflow. Julia does have a window of opportunity today and Wednesday to intensify into a Category 2 hurricane before the shear rises.

Elsewhere in the tropics
The GFS and ECMWF models are suggesting the possibility of a new tropical depression forming a few hundred miles off the coast of Africa about seven days from now.

"Hurricane Haven" airing this afternoon
Tune in to my live Internet radio show, "Hurricane Haven", airing at 4pm EDT today. If you want to ask a question, the call in number is 415-983-2634, or you can email a question to broadcast@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line.

Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have a new post on Wednesday morning.

Jeff Masters

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Quoting Tazmanian:
i take back my last post about the banned thing lol


You're a good man Taz.
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1969. SLU
...INITIAL CONDITIONS...

LATCUR = 18.9N LONCUR = 53.5W DIRCUR = 295DEG SPDCUR = 8KT
LATM12 = 18.1N LONM12 = 52.0W DIRM12 = 300DEG SPDM12 = 7KT
LATM24 = 17.7N LONM24 = 50.9W
WNDCUR = 135KT RMAXWD = 25NM WNDM12 = 115KT
CENPRS = 925MB OUTPRS = 1010MB OUTRAD = 325NM SDEPTH = D
RD34NE = 195NM RD34SE = 150NM RD34SW = 130NM RD34NW = 160NM
Member Since: Posts: Comments:
1968. leo305
Quoting CybrTeddy:


Incorrect

AL, 11, 2010091500, , BEST, 0, 189N, 535W, 135, 925, HU


I meant they haven't released an advisory upgrading the system to 155MPH
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting KerryInNOLA:
Igor's eye now has a flying saucer shape. Could that mean something?


What bar you hang out in? I reallyyyyy need to visit it!
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15/0000 UTC 16.5N 30.5W T5.0/5.0 JULIA -- Atlantic
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Quoting CybrTeddy:

AL, 11, 2010091500, , BEST, 0, 189N, 535W, 135, 925, HU

The first since Felix in 2007
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Wow!

14/2345 UTC 18.9N 53.4W T7.0/7.0 IGOR
Member Since: June 9, 2007 Posts: 4 Comments: 15947
Quoting Tazmanian:



but with T # at 7.0 they may go with winds of 160mph


Correct, and I highly suspect it will. If that is the case, expect a special advisory.
Member Since: July 8, 2005 Posts: 259 Comments: 24548
Quoting leo305:


NHC have not upgraded the system to 155, they have it at 145

and infared shows although convection is becoming heavier around the core of the system, the eye is becoming less organized, and so is the overall structure of the hurricane.



No. That was the 5:00 Update, satellite estimates were 10 to 15 knots lower at that time then they are now...
Member Since: August 21, 2008 Posts: 0 Comments: 7969
Quoting Hurricanes101:
anyone have radar loops for Mexico?


Here is a radar for Cancun.

And one for Belize.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
1959. bird72
So many dynamic forces interacting there, looks a little difficult to forecast something out of this! lol.


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Raw T is up to 7.1

Member Since: June 9, 2007 Posts: 4 Comments: 15947
Quoting CybrTeddy:


Incorrect

AL, 11, 2010091500, , BEST, 0, 189N, 535W, 135, 925, HU



but with T # at 7.0 they may go with winds of 160mph
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1956. SLU
14/2345 UTC 18.9N 53.4W T7.0/7.0 IGOR

This would make IGOR the 1st category 5 "supercane" to form east of 60W, south of 20N since MH HUGO in September 1989.
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Whoa. I've been gone since the morning and a LOT has happened since. Holy pants! Igor is twice as huge and is wasting no time in re-strengthening, and is probably 90% more likely to become a category 5, and Karl has finally formed when 92L looked so bleak earlier today - and he is wasting no time either, he's like quadrupled his size. Mexico should be very, very happy he's moving so fast. I'd be worried.

Sorry about the "urgent" tone here folks, I'm just rather impressed.
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1954. FLDART1
evening gang...
Member Since: August 4, 2007 Posts: 0 Comments: 201
Igor's eye now has a flying saucer shape. Could that mean something?
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Quoting Tazmanian:



7.1?


Yea, very impressive its ramped up so quickly the last few hours. We haven't seen a Category 5 in 3 years, looks like we'll get one tonight.
Member Since: July 8, 2005 Posts: 259 Comments: 24548
Quoting Levi32:
14/2345 UTC 18.9N 53.4W T7.0/7.0 IGOR


I spoke too soon!
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2010SEP15 001500 6.7 931.0/ +1.6 /132.2 6.7 7.1 7.1 NO LIMIT OFF OFF 13.64 -73.61 EYE 27 IR 18.90 53.40 COMBO
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1949. Max1023
2010SEP15 001500 6.7 931.0/ +1.6 /132.2 6.7 7.1 7.1 NO LIMIT OFF OFF 13.64 -73.61 EYE 27 IR 18.90 53.40 COMBO

That's 2 in a row over 7, and the eye has only cooled because that massive hot tower has compressed it a bit.
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Quoting Grecojdw:
I'm actually weary of the pattern change hinted in Levi's blogs he's been explaining. Us from the Houston East to Florida might get a shock at the latter end of September. Quite nervous currently since most of the predictions this season that have transpired so far came true:0
Actually, dunno about that... seems that the only one NOT true so far is the one about the US landfalls.
Member Since: October 25, 2005 Posts: 19 Comments: 22682
Quoting leo305:


NHC have not upgraded the system to 155, they have it at 145

and infared shows although convection is becoming heavier around the core of the system, the eye is becoming less organized, and so is the overall structure of the hurricane.


Incorrect

AL, 11, 2010091500, , BEST, 0, 189N, 535W, 135, 925, HU
Member Since: July 8, 2005 Posts: 259 Comments: 24548
Quoting CybrTeddy:
SAB is the naturally more conservative one, SAB is at 7.0 we're probably looking at Category 5 Hurricane Igor.

Wow! Never seen SAB at 7.0. But I found out about SAB and TAFB this year so...
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting CybrTeddy:


Satellite estimates disagree with you, and so is the NHC right now. 155 mph, so its 1 mph short of Category 5.

Looks like a CAT 5 to me

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Quoting Stormchaser2007:
2010SEP15 001500 6.7 931.0/ +1.6 /132.2 6.7 7.1 7.1



7.1?
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1943. leo305
Quoting CybrTeddy:


Satellite estimates disagree with you, and so is the NHC right now. 155 mph, so its 1 mph short of Category 5.


NHC have not upgraded the system to 155, they have it at 145

and infared shows although convection is becoming heavier around the core of the system, the eye is becoming less organized, and so is the overall structure of the hurricane.
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting Levi32:


Not necessarily, but if such an error continues over time you know the models have a problem. For example, the models have been consistently 20-30 miles too far northeast in the very short-term forecasts for most of Igor's life, and ultimately the initial long-range forecasts ended up 10 degrees too far east for Igor's recurve. If such errors continue over the next couple days, then it is likely that the entire recurve will again take place farther west than the models have it now, hopefully far enough west to spare Bermuda a direct hit.


Levi- how far west can Igor go before he recurves if we are to be spared a hit in Nova Scotia? It seems to me (an amateur) that the longer he takes to really start turning. the greater the chance we have of being smacked? As it is with the current NHC track, he will pass too close for comfort so the margin of error would seem to be small?
Thanks!
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Quoting StormW:


It's forecast to hang around that area or centered just north of Louisiana for at least the next 96 hours

okayso we've got at least 4 days...so that SHOULD be enough to keep Karl out of our backyard, correct? :))))
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1940. bwat
notice the temps of the northern eyewall towards the end.
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i take back my last post about the banned thing lol
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2010SEP15 001500 6.7 931.0/ +1.6 /132.2 6.7 7.1 7.1
Member Since: June 9, 2007 Posts: 4 Comments: 15947
Quoting JupiterFL:


Its not jealousy. Its purely to pick a fight. Thats it. Distract the blog and push it into a direction where no one wishes to go. Thats it pure and simple. See these "trolls" hide behind their computer screens because they would never confont someone in real life. They are real life pansies trying to be computer tough guys.


another 1000
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1936. JLPR2
Quoting StormW:


Wanted to pick your brain (I know you need it for Calculus), but looking at the way the trof is going zonal along the base, if he goes CAT 5, think he may "eat" the trof?


Isabel Style? As in busting it.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Long Range GFS was showing a hurricane hitting Southwest Florida around the 26th of September, newest runs showing the same hurricane taking a similar course to Karl and hitting Mexico. Based on patterns this year, this sounds like a likely scenario as every storm is either a fish or a Mexican cutie.
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.
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Quoting leo305:
the structure is getting worse so I doubt it's getting stronger


Satellite estimates disagree with you, and so is the NHC right now. 155 mph, so its 1 mph short of Category 5.
Member Since: July 8, 2005 Posts: 259 Comments: 24548
..
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.
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Quoting Max1023:
I meant the raw numbers, 7.0 is 140 knots


It showed 6.7,7.0,7.0, What is it now?
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Quoting Levi32:
By Dvorak estimates we have ourselves a Cat 5 hurricane.



whats slow down there and wait for the nhc K?
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Quoting Tazmanian:



reported you be banned soon for posting that



During active periods of hurricane season, these rules will be strictly enforced. Violations will be met with a minimum 24 hour ban


It must be impossible to get banned today. Otherwise several people would have been sent to jail........like Jeff.
Member Since: November 18, 2007 Posts: 0 Comments: 1030
1927. lennit
see when you work in this field weather forecasters are like doctors...everyone has an idea what they diagnosis but try not to step on toes of each others for each has there own analysis of whats going on.. that how you can tell the real from the imposters on the blog..
Member Since: October 28, 2007 Posts: 0 Comments: 101
SAB is the naturally more conservative one, SAB is at 7.0 we're probably looking at Category 5 Hurricane Igor.
Member Since: July 8, 2005 Posts: 259 Comments: 24548
1925. Grothar
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Quoting Levi32:


Well that's asking for a lot. We're talking about 650 miles between Cape Hatteras and Bermuda, which means tropical storm force winds would have to extend out 325 miles to the west of the storm....very hard to pull off. Currently they extend out just over 200 miles, and the east side will have to greatest extent when the storm turns north.


Levi, LOVE your TIDBITS!! Love looking at your videos....GOOD job, you are a very knowledgeable young man!!!!
Member Since: June 16, 2008 Posts: 0 Comments: 507
Quoting Tazmanian:



reported you be banned soon for posting that



During active periods of hurricane season, these rules will be strictly enforced. Violations will be met with a minimum 24 hour ban


Lighten up taz lol!
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Quoting Levi32:
By Dvorak estimates we have ourselves a Cat 5 hurricane.

Yikes!
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Quoting Tazmanian:



reported you be banned soon for posting that



During active periods of hurricane season, these rules will be strictly enforced. Violations will be met with a minimum 24 hour ban


what in the world are you talking about?
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1920. leo305
the structure is getting worse so I doubt it's getting stronger
Member Since: April 17, 2010 Posts: 0 Comments: 1753

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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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