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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1546. IKE
Morehead City,NC extended...maybe this front gives Igor one last kick north and then NE........

LONG TERM /WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 300 PM SUNDAY...NOT MUCH CHANGE IN EXTENDED FORECAST
THINKING FROM YESTERDAY. UPPER FLOW WILL REMAIN RELATIVELY ZONAL
UNTIL H5 HEIGHTS START TO RISE BY NEXT WEEKEND. GFS/ECMWF AND HPC
GUIDANCE INDICATE SURFACE RIDGE TO LINGER JUST OFFSHORE THURSDAY
BEFORE MOVING OFFSHORE THURSDAY NIGHT. THIS ALLOW A COLD FRONT TO
MOVE INTO THE REGION FRIDAY AND OFFSHORE EARLY SATURDAY.
CONTINUED
WITH SMALL POPS FOR THE FRIDAY THRU SATURDAY TIME FRAME...WITH
REMAINDER OF EXTENDED PERIOD DRY. TEMPS WILL REMAIN NEAR OR
SLIGHTLY ABOVE SEASONAL NORMALS.
-- End Changed Discussion --

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I think I know the answer to this question but gonna ask anyway. As long as there is adequate jet fuel and the right conditions, can a hurricane like Igor maintain its itensity all the way of a CONUS landfall (if that were to happen), with eyewall cycle changes etc..? I remember Dean and Felix seemed to be monsters long before they both hit Mexico.
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1542. IKE
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Quoting CosmicEvents:
TD OR NOT TD, that is the Shakesperean tropical question.


;P
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Looks like a huge ACE producer.
Member Since: June 9, 2007 Posts: 4 Comments: 15946
1538. IKE
THE NHC TRACK FORECAST IS NUDGED TO THE RIGHT OF
THE PREVIOUS FORECAST AFTER DAY 3...CLOSER TO THE TVCN CONSENSUS
MODEL...BUT STILL TO THE LEFT OUT OF RESPECT TO THE RELIABLE ECMWF
MODEL.


Hmm...nudged the track forecast to the right. I guess the NHC isn't buying into west-casting this afternoon.
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Quoting CosmicEvents:
TD OR NOT TD, that is the Shakesperean tropical question.
"It is the green-ey'd monster, which doth mock the meat it feeds on.".....gulp....hope Igor doesn't reach the green eye stage!
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000
WTNT32 KNHC 122037
TCPAT2
BULLETIN
TROPICAL DEPRESSION TWELVE ADVISORY NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010
500 PM AST SUN SEP 12 2010

...DEPRESSION NEAR TROPICAL STORM STRENGTH...WILL PASS NEAR THE
SOUTHERN CAPE VERDE ISLANDS TONIGHT AND EARLY MONDAY...


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Quoting Stormchaser2007:
RI has stopped.

For now...


Final T# Adj T# Raw T#
6.4 6.4 6.4

It just went up a little more.

CI# /Pressure/ Vmax
6.5 / 937.0mb/127.0kt



Final T# Adj T# Raw T#
6.5 6.5 6.5
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Stormchaser2007:
Peak 135 knots.

Wow
Yeah, 155mph. 1mph shy of category 5 status.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Peak 135 knots.

Wow
Member Since: June 9, 2007 Posts: 4 Comments: 15946
Quoting IpswichWeatherCenter:


It seems to be a combination of it being stubborn, dry air, shear and land interaction.

Thank god Igor isn't there right now - lives would truly be in danger. And we'd have a huge cyclone on our hands.
Maybe it wont have a "mysterious night" tonight and develop, like the good Doc posted this morning.
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RI has stopped.

For now...


Final T# Adj T# Raw T#
6.4 6.4 6.4

Member Since: June 9, 2007 Posts: 4 Comments: 15946
000
WTNT41 KNHC 122038
TCDAT1
HURRICANE IGOR DISCUSSION NUMBER 19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010
500 PM AST SUN SEP 12 2010

IGOR CONTINUES TO INTENSIFY AT A RAPID PACE. DVORAK INTENSITY
ESTIMATES AND THE UW-CIMSS ADT HAVE INCREASED FURTHER...AND THE
INITIAL INTENSITY IS ADJUSTED SLIGHTLY UPWARD TO 120 KT BASED ON A
COMPROMISE OF THESE DATA AND THE LATEST SATCON INTENSITY ESTIMATE.
THE OFFICIAL INTENSITY FORECAST HAS ALSO BEEN ADJUSTED TO SHOW SOME
FURTHER STRENGTHENING AND A PEAK INTENSITY AT DAY 3 OF 135
KT...SIMILAR TO SHIPS MODEL. FOR THE REMAINDER OF THE PERIOD...THE
OFFICIAL FORECAST CALLS FOR SOME GRADUAL WEAKENING AND IS BASED
PRIMARILY ON THE ICON CONSENSUS MODEL. IT IS WORTH NOTING THAT
FLUCTUATIONS IN STRENGTH DUE TO EYEWALL REPLACEMENT CYCLES ARE
POSSIBLE...HOWEVER...THERE IS LITTLE SKILL IN FORECASTING THE
TIMING OF THESE CYCLES.

THE INITIAL MOTION ESTIMATE REMAINS 270/12. THE TRACK FORECAST
PHILOSOPHY REMAINS UNCHANGED FOR THIS ADVISORY...HOWEVER THERE IS
STILL CONSIDERABLE DYNAMICAL MODEL SPREAD AFTER 36 HOURS. THE
HWRF...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. THE NHC TRACK FORECAST IS NUDGED TO THE RIGHT OF
THE PREVIOUS FORECAST AFTER DAY 3...CLOSER TO THE TVCN CONSENSUS
MODEL...BUT STILL TO THE LEFT OUT OF RESPECT TO THE RELIABLE ECMWF
MODEL.

FORECAST POSITIONS AND MAX WINDS

INITIAL 12/2100Z 17.7N 46.9W 120 KT
12HR VT 13/0600Z 17.8N 48.7W 125 KT
24HR VT 13/1800Z 18.1N 50.8W 125 KT
36HR VT 14/0600Z 18.7N 52.6W 130 KT
48HR VT 14/1800Z 19.4N 54.3W 130 KT
72HR VT 15/1800Z 21.3N 57.1W 135 KT
96HR VT 16/1800Z 23.5N 60.0W 125 KT
120HR VT 17/1800Z 25.8N 62.9W 120 KT

$$
FORECASTER ROBERTS/BRENNAN
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1528. will40
Quoting stormpetrol:
anyone know if the HHs are still flying into 92L tonight?



ATLANTIC REQUIREMENTS
1. SUSPECT AREA (CENTRAL CARIBBEAN)
FLIGHT ONE -- TEAL 70
A. 12/1800Z
B. AFXXX 01EEA INVEST
C. 12/1145Z
D. 15.5N 70.0W
E. 12/1700Z TO 12/2100Z
F. SFC TO 10,000 FT

was scheduled this afternoon but i think it got canceled
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1527. leo305
Igor has been moving a tad south of due west for a while now
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...LARGE AND POWERFUL IGOR MOVING WESTWARD OVER THE CENTRAL TROPICAL
ATLANTIC...

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...17.7N 46.9W
ABOUT 1065 MI...1715 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/HR
PRESENT MOVEMENT...W OR 270 DEGREES AT 14 MPH...22 KM/HR
MINIMUM CENTRAL PRESSURE...942 MB...27.82 INCHES


...DEPRESSION NEAR TROPICAL STORM STRENGTH...WILL PASS NEAR THE
SOUTHERN CAPE VERDE ISLANDS TONIGHT AND EARLY MONDAY...

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...13.3N 22.8W
ABOUT 150 MI...240 KM SE OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/HR
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting NCHurricane2009:


LOL! I hate 92L too! Make up your mind, and quit reading shakespeare "to be or not to be, that is the question." From now on, I am classifying disturbances like 92L as Shakesperean tropical disturbances.
TD OR NOT TD, that is the Shakesperean tropical question.
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Quoting BVImom:
Afternoon WU people. As of yesterday Igor (the ghastly) looked forecast to pass several hundred miles to our north east. Today looks like he may take a passing swipe. Any comments and advice?
Prolly something like

INTERESTS IN THE BVI SHOULD MONITOR THE PROGRESS OF MAJOR HURRICANE IGOR....

Frankly, wouldn't be surprised to see something similar posted by Wednesday latest. But there's still a huge amount of variability possible with this system. Best just to keep the wx eye out...
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anyone know if the HHs are still flying into 92L tonight?
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Quoting NCHurricane2009:


I take it from your name that you live in the British Virgin Islands? (BVImom). In that case, it still looks like Igor should pass to the north of you, and bring lots of sea swells to beaches no matter what. So don't be out in the water when local officials post rip current and surf warnings on your beaches. Although its really unlikely Igor will bring direct weather to your area (i.e. clouds rain and wind), as always, you should keep an eye on the storm. If it doesn't start turning north even a little bit by the time its nearing 57W longitude, then that's when it seems Igor will start to possibly bring direct weather impacts to your area. Till then, just keep an eye on its eye (no pun intended).

With a storm this far out, always watch it to make sure forecasts are verifying.


Well said.
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12L remains a tropical depression.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Holy Moly, all I did was go to work for a few hours, and Igor blew up!
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No stick throwing please. But to my very untrained eye, it looks like 92L has become an open wave and has gone the way of Gaston, is this a correct obs?
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Quoting NCHurricane2009:


If we get 8 storms in September, that'll tie the record as the most September storms for the Atlantic, tying with 1998, 2002, and 2007.
Yeah, I know. I don't see why it can't happen. In fact, I wouldn't be surprised to see a new record there. U do realize it is only SEP 10th, right? We have 20 days left, with yet another AEW set to exit and potentially become another storm; we still can't rule out development of our monsoonal 92L, especially after passage into the WCar and BoC... that's potentially two more storms before the 17th.... I'm not seeing so much a stopping or slowing of the season as a transferral of TC formation location...

But, we shall see...
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Quoting BVImom:
Afternoon WU people. As of yesterday Igor (the ghastly) looked forecast to pass several hundred miles to our north east. Today looks like he may take a passing swipe. Any comments and advice?


I take it from your name that you live in the British Virgin Islands? (BVImom). In that case, it still looks like Igor should pass to the north of you, and bring lots of sea swells to beaches no matter what. So don't be out in the water when local officials post rip current and surf warnings on your beaches. Although its really unlikely Igor will bring direct weather to your area (i.e. clouds rain and wind), as always, you should keep an eye on the storm. If it doesn't start turning north even a little bit by the time its nearing 57W longitude, then that's when it seems Igor will start to possibly bring direct weather impacts to your area. Till then, just keep an eye on its eye (no pun intended).

With a storm this far out, always watch it to make sure forecasts are verifying.
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Quoting RecordSeason:


Actually, the SE quadrant of Igor has pretty consistently been 5 to 10 Celsius colder convection than any other quadrant, particularly in the 1945 IR frame, so I don't know what you're looking at.


It looks slightly more ragged to me. But I'm probably wrong - Its very late where I am and I'm tired.
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Quoting anyotherliestotell:
there is absolutely NO chance Igor will hit Florida. NONE.


You mind if I borrow your crystal ball...I could sure use the lottery numbers!!
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Quoting Vero1:


Left of the "High Seas"

South Atlantic is always kissing the hot carribean !!!
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Quoting NCHurricane2009:
My theory with 92L,:

Its like, water too hot, ouch, ooh, getting burned, help me! Hey, maybe tropical systems don't like touching hot water just like humans don't like to put their hand on a burning stove!

Just Kidding. I really want to know why 92L hasn't developed yet. I am glad it hasn't, but I am always a "why" person, I want explanations.


It seems to be a combination of it being stubborn, dry air, shear and land interaction.

Thank god Igor isn't there right now - lives would truly be in danger. And we'd have a huge cyclone on our hands.
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Is that a purple hippo I spy?!?!

LOL
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http://www.ssd.noaa.gov/goes/east/nwatl/vis-l.jpg

In that satellite image, you can barely see Igor's eye in the lower-right corner. Its like Igor is saying, "wazzup?!! I am here!"
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BahaHurican: you are right about the models. Earl was barely inside the southern edge of what had been the 5-day cone; it was supposed to miss the Leeward Islands, and I for one was a little surprised by the fact that they got hit. It looks like the islands will be safe this time, but we're bascially talking about 8 days from now in terms of what happens next. Once that NW turn starts, then we'll be looking at 3-5 day forecasts again, and the certainty will certainly be enough.
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1502. leo305
92L is looking a lot more organized.. perfect outflow, and it feels like it's going to really develop tonight
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1501. BVImom
Afternoon WU people. As of yesterday Igor (the ghastly) looked forecast to pass several hundred miles to our north east. Today looks like he may take a passing swipe. Any comments and advice?
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1499. Max1023
Quoting IpswichWeatherCenter:
If I were the NHC I would be considering 150mph right now. The 2 meso-vortices and the almost perfect organisation of the storm certainly merit it. However the Southern Section of the Storm certainly doesn't do it any favours - its clearly the weakest part of the storm.


The "weakest" part of the storm would be enough to make a 115 knot storm if it went the whole way around. Also the southern eyewall has cooled recently. Igor is most of the way to the "Pink Ring of Devastation" on WU IR.
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1498. xcool


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My theory with 92L,:

Its like, water too hot, ouch, ooh, getting burned, help me! Hey, maybe tropical systems don't like touching hot water just like humans don't like to put their hand on a burning stove!

Just Kidding. I really want to know why 92L hasn't developed yet. I am glad it hasn't, but I am always a "why" person, I want explanations.
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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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