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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2373. Vero1
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 12 2010

...SPECIAL FEATURES...

THE CENTER OF HURRICANE IGOR AT 12/0900 UTC IS NEAR 17.7N 44.4W.
IGOR IS MOVING WESTWARD 16 KT. THIS POSITION IS ABOUT 990 NM TO
THE EAST OF THE NORTHEASTERN CARIBBEAN SEA ISLANDS. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 992 MB.
THE MAXIMUM SUSTAINED WIND
SPEEDS ARE 70 KT WITH GUSTS TO 85 KT. PLEASE READ THE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/
WTNT31 KNHC AND THE FULL FORECAST AND ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. STRONG RAIN-
SHOWERS AND THUNDERSTORMS ARE FROM 16N TO 19N BETWEEN 42W AND
48W. OTHER RAINSHOWERS AND THUNDERSTORMS ARE FROM 10N TO 14N
BETWEEN 30S AND 47W...AND FROM 18N TO 22N BETWEEN 30W AND 47W.

A 1008 MB LOW PRESSURE CENTER IS NEAR 16N69W...ABOUT 180 NM TO
THE SOUTH OF THE DOMINICAN REPUBLIC. STRONG RAINSHOWERS AND
THUNDERSTORMS COVER THE AREA FROM 14N TO 18N BETWEEN 67W AND 74W.
LOCALLY HEAVY RAINFALL IS POSSIBLE IN THE VIRGIN ISLANDS...
PUERTO RICO...AND HISPANIOLA DURING THE NEXT DAY OR SO. THESE
RAINS MAY CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...
ESPECIALLY IN MOUNTAINOUS TERRAIN. IT IS POSSIBLE THAT
A TROPICAL DEPRESSION MAY FORM DURING THE NEXT 48 HOURS.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 17N19W 8N20W MOVING
WESTWARD 10 KT. A 1006 MB LOW PRESSURE CENTER IS ALONG THE WAVE
NEAR 13N. IT IS POSSIBLE THAT THIS FEATURE MAY TURN INTO
A TROPICAL CYCLONE DURING THE NEXT 24 HOURS...AND IT MAY BE
NECESSARY TO ISSUE ADVISORIES AT ANY TIME TODAY. ANYONE WHO IS
IN THE CAPE VERDE ISLANDS SHOULD MONITOR CLOSELY THE PROGRESS
OF THIS SYSTEM IN CASE WATCHES OR WARNINGS ARE REQUIRED. PLEASE
READ THE LATEST TROPICAL WEATHER OUTLOOK UNDER AWIPS/WMO HEADERS
MIATWOAT/ABNT20 KNHC FOR MORE DETAILS. NUMEROUS STRONG
RAIN-SHOWERS AND THUNDERSTORMS ARE FROM 13N TO 17N BETWEEN 18W
AND 23W...RIGHT AT THE EASTERN EDGE OF THE CAPE VERDE ISLANDS.

Member Since: Posts: Comments:
The eye isn't that big, its just Igor's pretty small.

Member Since: July 8, 2005 Posts: 259 Comments: 23956
2371. Relix
Quoting Ryuujin:
Since Igor is already so strong, wouldn't that reinforce the idea that he'll pump the ridge above him, which in turn will push him further west?


There is no way he's missing this hole:

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2370. Ryuujin
Double post
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2369. Ryuujin
Since Igor is already so strong, wouldn't that reinforce the idea that he'll pump the ridge above him, which in turn will push him further west?
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Quoting Cotillion:
BEGIN
NHC_ATCF
invest_RENUMBER_al932010_al122010.ren
FSTDA
R
U
040
010
0000
201009121234
NONE
NOTIFY=ATRP
END

Finally!
Member Since: July 7, 2010 Posts: 0 Comments: 5675
With Igor's very large eye, is it a matter of waiting for the winds to catch up? (I presume the storm is too far out for HH planes, so we don't know the central pressure?)
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invest_RENUMBER_al932010_al122010.ren

TD12 is born and Igor is a Category 2.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
Quoting Cotillion:
BEGIN
NHC_ATCF
invest_RENUMBER_al932010_al122010.ren
FSTDA
R
U
040
010
0000
201009121234
NONE
NOTIFY=ATRP
END


So TD 12 is born...
Member Since: Posts: Comments:
BEGIN
NHC_ATCF
invest_RENUMBER_al932010_al122010.ren
FSTDA
R
U
040
010
0000
201009121234
NONE
NOTIFY=ATRP
END
Member Since: Posts: Comments:
Quoting Thundercloud01221991:



they said Earl???


Ack! No, they said Igor. Sorry, coffee is 'perking' so I havent' had my first cup yet. Should have waited until I had some before posting.
Member Since: August 22, 2009 Posts: 0 Comments: 3115
Quoting CybrTeddy:


Assuming the ADT isn't off its rocker, it would be a average of 5.0, so yea 90 knots.


Which is a Category 2 storm...
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We 'should' see a renumber shortly, as 93L is continuing to become better organized.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
Quoting Cotillion:
AL, 11, 2010091212, , BEST, 0, 177N, 449W, 85, 975, HU, 64, NEQ, 30, 15, 15, 20,

Category Two.


and it still has 2 and a half hours to strengthen before the advisory comes out
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Quoting Snowlover123:


And blending them together would equate to roughly 90 kts.

-Snow


Assuming the ADT isn't off its rocker, it would be a average of 5.0, so yea 90 knots.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
Quoting HurricaneSwirl:


Here's an elaborate chart you may wanna bookmark: Link


thank you!!!
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AL, 11, 2010091212, , BEST, 0, 177N, 449W, 85, 975, HU, 64, NEQ, 30, 15, 15, 20,

Category Two.
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Quoting WeatherNerdPR:

Oh My God.


The sat pics tell the story here. Should not be a big surprise. Igor likely (IMO) goes to cat 3 by end of day.
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Quoting jodi4lsu:


thank you so much...i appreciate all of you who take time to explain these things to people like me!


Here's an elaborate chart you may wanna bookmark: Link
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2353. Relix
Any changes with Igor's track?

Good Morning StormW and everyone!
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Quoting aislinnpaps:
Good morning, everyone. Woke up and glanced at the paper this morning and they have Earl heading west and is 'one to watch'. Nothing about the track has him turning north eventually or that he won't be giong into thr GOMEX. They don't mention anything else in the tropics. Gotta love the media sometimes.



they said Earl???
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Happy Sunday everyone!

First stupid question of the day.

Is there a greater amount of dry air around this year? (I don't remember this amount of talk about air in the past)

And is it a result of the record high temperatures we've been having?

Been wondering and have no clue who to ask.
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Quoting CybrTeddy:
SAB at 4.5 for Igor, or 77 knots.


And blending them together would equate to roughly 90 kts.

-Snow
Member Since: Posts: Comments:
Good morning, everyone. Woke up and glanced at the paper this morning and they have Earl heading west and is 'one to watch'. Nothing about the track has him turning north eventually or that he won't be giong into thr GOMEX. They don't mention anything else in the tropics. Gotta love the media sometimes.
Member Since: August 22, 2009 Posts: 0 Comments: 3115
SAB supports a 90 mph system right now. Wondering what the TAFB will say.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
SAB at 4.5 for Igor, or 77 knots.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
ADT jumping through the roof is no surprise. As soon as any hurricane gets a well defined eye, it always does.
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Impressive. Nice feeder band to its west, and a very large eye, for such a small system. Looks like a miniture Katrina almost!
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Impressive. Nice feeder band to its west, and a very large eye, for such a small system. Looks like a miniture Katrina almost!
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Quoting Thundercloud01221991:


well the 5.5 is a satellite estimated number equivalent to strength of a system

example is 2.5 is usually a TS
4.0 is usually a hurricane
5.5 is usually Cat 3
6.0 is usually Cat 4
6.5-8.0 is usually Cat 6

the 102.0 knts are estimated wind speed ~117 mph


thank you so much...i appreciate all of you who take time to explain these things to people like me!
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Quoting Snowlover123:


Okay... we'll see... when do they come out?


I think momentarily.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
12/1145 UTC 17.7N 44.8W T4.5/4.5 IGOR -- Atlantic
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Quoting jodi4lsu:


i'm very new at this weather watching....could you explain these numbers to me? i understand the pressure, the lower it is, the stronger the storm, but the other 2? thanks


well the 5.5 is a satellite estimated number equivalent to strength of a system

example is 2.5 is usually a TS
4.0 is usually a hurricane
5.5 is usually Cat 3
6.0 is usually Cat 4
6.5-8.0 is usually Cat 6

the 102.0 knts are estimated wind speed ~117 mph
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Quoting Snowlover123:


Superheated waters, low shear, no dry air... etc. and it may impact land... Bermuda, or the Eastern Seaboard...

So it could have an Earl-Like Track or a Fabian-Like Track?
Member Since: July 7, 2010 Posts: 0 Comments: 5675
Quoting CybrTeddy:


Unless the SAB and the TAFB come out with a 5.5 we don't.


Okay... we'll see... when do they come out?
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Quoting SevereWeather:
12/1145 UTC 15.7N 70.7W T1.5/1.5 92L -- Atlantic

Stronger than yesterday, they had it a TOO WEAK.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Snowlover123:


This is also in agreement with the 5.3 CyberTed showed before. I think we have a major hurricane on our hands, folks. Storm, can you confirm? :)


Unless the SAB and the TAFB come out with a 5.5 we don't.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
12/1145 UTC 15.7N 70.7W T1.5/1.5 92L -- Atlantic
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Quoting WeatherNerdPR:

Geee. I wonder why. lol


Superheated waters, low shear, no dry air... etc. and it may impact land... Bermuda, or the Eastern Seaboard...
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Quoting StormW:
I will have a synopsis out in about 15-20 min.

I'll be back later this afternoon and try to field questions then.


Ok; Thanks StormW
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Quoting Thundercloud01221991:
CI# /Pressure/ Vmax
5.5 / 962.0mb/102.0kt


Major Hurricane anyone???


Well, it certainly LOOKS like one--significant organization/strengthening overnight. It just where I like to see the big ones--not a threat to the Antilles, and we'll pray Bermuda gets spared.
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Quoting Thundercloud01221991:
CI# /Pressure/ Vmax
5.5 / 962.0mb/102.0kt


Major Hurricane anyone???


i'm very new at this weather watching....could you explain these numbers to me? i understand the pressure, the lower it is, the stronger the storm, but the other 2? thanks
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Quoting Thundercloud01221991:
CI# /Pressure/ Vmax
5.5 / 962.0mb/102.0kt


Major Hurricane anyone???


This is also in agreement with the 5.3 CyberTed showed before. I think we have a major hurricane on our hands, folks. Storm, can you confirm? :)
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Quoting Snowlover123:


I believe we have a rapid deepening system on our hands. The advisory stated that Igor had pressures of 988 mb. Now T-NUMBERS are showing 966 mb? A drop of 22 mb in a few hours? O.o


Raw T# have a tendency to jump the gun. If the TAFB and SAB have a 6.0 then we are.
Member Since: July 8, 2005 Posts: 259 Comments: 23956
don't be surprise if igor were to take a south of west jog today or tomorrow
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Quoting Snowlover123:


I think it has an excellent shot at Cat 5... like Ivan...

-Snow

Geee. I wonder why. lol
Member Since: July 7, 2010 Posts: 0 Comments: 5675
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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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