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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896. MZT
Quoting PensacolaDoug:
IGOR 950 cat4 - ALEX Cat2 at 947....

Odd......

Alex did not have room to run in the bay of Campeche. His winds would have matched that pressure if he'd had one more night over water.
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Igor will probably be the first category 5 Hurricane since Wilma of 2005!
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Run for the hills!!!!!!!!A monster is coming!!!!!IGOR!!!!!!!!!!!!
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OMG! CAT4! 14% chance of Cat5. Explosive Deepening. Igor is a beautiful BEAST!
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Quoting nash28:


Why is everyone having such a hard time with the name of this storm? It's IGOR! LOL!





losin' the bubble?
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Quoting MiamiHurricanes09:
WOW, that's 127kt (146mph) hurricane. This thing is definitely making a great run for category 5 status.

119.8KTS~138 MPH

So at 12:15PM CDT we have a CAT 4 w/140MPH winds and a central pressure of 945MB!! AMAZING :O)!!
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HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 40 MILES...65 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 160
MILES...260 KM.

It's not that big. That'll help him achieve any greater intensity.

The pressure's a little bit high for a usual Cat 4, but it's not that uncommon.
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Quoting nash28:


Why is everyone having such a hard time with the name of this storm? It's IGOR! LOL!
LOL! I'm already getting used to it.
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LOL, I'm sorry, Earl is still on my mind... ;)
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Quoting weatherlover94:


i have to agree with you but its getting very frighting


it all depends on what model the NHC is leaning to. The track right now has a lot of GFS bias IMO
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Quoting Hurricanes12:
MH09, Is there any possibility of Earl hitting Florida?

It's Igor, IGOR!! Lol.

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Storm W,
Since it appears that Igor is obtaining Cat 4 and still could get stronger, how much effect would "Pumping the Ridge" have on its movement. Expecially if and when he would fell the effects of any troughs?
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Quoting nash28:


Why is everyone having such a hard time with the name of this storm? It's IGOR! LOL!


Been like that all day!
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Quoting Hurricanes12:
MH09, Is there any possibility of Earl hitting Florida?

No Zero Nada.
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----- Current Analysis -----
Date : 12 SEP 2010 Time : 171500 UTC
Lat : 17:39:53 N Lon : 45:56:42 W


CI# /Pressure/ Vmax
6.2 / 944.8mb/119.8kt


Final T# Adj T# Raw T#
6.2 6.5 6.5

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Igor is impatient ... way ahead of schedule
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Quoting Hurricanes12:
MH09, Is there any possibility of Earl hitting Florida?


Why is everyone having such a hard time with the name of this storm? It's IGOR! LOL!
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Quoting MiamiHurricanes09:
WOW, that's 127kt (146mph) hurricane. This thing is definitely making a great run for category 5 status.

Possibly a strong cat. 4 by 5pm.
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I've been reading about the elimination criterion for declaring (or, that is, not declaring) a hurricane as annular:

--SSTs can't be below 25.4.C or higher than 28.5.C;
--Winds can't be below 85 knots or higher than 125 knots;
--Deep-layer (850-200 mb) wind shear can't be greater than 23.9 knots;
--Generalized wind shear can't be greater than 30.7 knots;
--The 200 mb zonal wind can't be less than -11 or greater than 17.2 knots;
--The radius of the coldest (brightest) cloud tops can't be less than 50 km;
--The REFC (Relative Eddy angular momentum Flux Convergence) can't be under -4.4 or greater than 8.4.

Not sure where Igor stands on all those, but I suspect he's pretty darn close...
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Quoting Hurricanes12:
MH09, Is there any possibility of Earl hitting Florida?
Yes. A very, very, slight one right now though.
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Nash I have said it before I say it again, humorous yes, but we do not have good luck with all these comically named storms
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ADT suggests 120 knots

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MH09, Is there any possibility of Earl hitting Florida?
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Quoting Stormchaser2007:
WOW. Raw T up 6.5

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 171500 UTC
Lat : 17:39:53 N Lon : 45:56:42 W


CI# /Pressure/ Vmax
6.2 / 944.8mb/119.8kt



Final T# Adj T# Raw T#
6.2 6.5 6.5

WOW, that's 127kt (146mph) hurricane. This thing is definitely making a great run for category 5 status.
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A 38MB pressure drop in 9.5 hrs!!! That is a whopping 4 MB an hour drop in pressure AMAZING!!!
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Quoting nash28:


Let's not get carried away.. Yes, the 12z CMC has shifted significantly to the left, but it is one run. We need to see how these troughs evolve or devolve as it were.


i have to agree with you but its getting very frighting
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Quoting KimberlyB:


I'm assuming you expect they will? Sorry, I haven't had a chance to go over to your update yet.


Storm likes to tease us in order to make us work harder at learning. He's a good teacher.
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Quoting MiamiHurricanes09:

@802.
Whispers...Wow. omg. Wow. wow.
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Quoting CosmicEvents:
It's true, everytime a Cat3 or higher that's ever come down the pike for the last 6 years this blog has thrown around the annular word.
.
.
So, please enlighten me. What would it mean right now if Igor was declared an annular hurricane? Besides being something of interest for mets. Would it effect track, intensity, etc?

Yes and yes Igor does resemble one of them though it probably has too much banding.
They look like donuts. are supercanes and can become annular and then go back to being just hurricanes. Wiki has a good explanation and here's a pdf of one. a-canes
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Quoting weatherlover94:
storm i dont know about you but i think this thing is headed for the us how about you?


I was thinking more along the lines of Bermuda getting wailed, but I could be wrong. Lord knows I'm no expert. ;)
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Really built the cloud shied right after the NHC cat 2 advisory.

Member Since: August 16, 2007 Posts: 6 Comments: 12463
oh yes if the models shift west then so does the forecast track making it even more frighting for us in the outer banks
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Quoting weatherlover94:
storm i dont know about you but i think this thing is headed for the us how about you?


Let's not get carried away.. Yes, the 12z CMC has shifted significantly to the left, but it is one run. We need to see how these troughs evolve or devolve as it were.
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92L is moving NW towards cuba
Member Since: April 17, 2010 Posts: 0 Comments: 1753
WOW. Raw T up 6.5

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 171500 UTC
Lat : 17:39:53 N Lon : 45:56:42 W


CI# /Pressure/ Vmax
6.2 / 944.8mb/119.8kt



Final T# Adj T# Raw T#
6.2 6.5 6.5

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Quoting KanKunKid:


Are you sure it's not a kid in his car with his sub-woofers blasting and shaking your pot and pans?

LOL!!
Nah! This is even better....
I may be forced to take a Siesta, shortly.
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whoaaaa.....look at Igor...holy smokes!
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so it's now..

9(10)
4
3
Member Since: April 17, 2010 Posts: 0 Comments: 1753
Quoting StormW:
Going to be interesting to see if the models shift left.


I'm assuming you expect they will? Sorry, I haven't had a chance to go over to your update yet.
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How probable or possible is to get Igor near Puerto Rico? Are we already safe from IGOR?
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storm i dont know about you but i think this thing is headed for the us how about you?
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It has a long ways to go.

Large ACE producer.


MAXIMUM SUSTAINED WINDS ARE NEAR 135 MPH...215 KM/HR...WITH HIGHER
GUSTS. IGOR IS A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON
HURRICANE WIND SCALE. SOME ADDITIONAL STRENGTHENING IS FORECAST
DURING THE NEXT 48 HOURS
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Quoting LongIslandXpress38:


Great update Levi. If your crazy Japanese model scenario pans out you should be Met. of the year!


I should point out that I haven't said the Japanese is right. I am pointing out the different scenarios that are possible and showing that what the Japanese has could make sense, and that's why the eastern seaboard should watch this very closely.
Member Since: November 24, 2005 Posts: 635 Comments: 26652
Quoting StormW:
Going to be interesting to see if the models shift left.


Howdy StormW!
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Quoting TropicalAnalystwx13:
Earl's a Cat. 4!


The only word that popped into my head was "DUH!" lol

He's looking all kinds of fine out there. I'm hoping and praying he stays far away from land. I don't think he will right now, but I'm sure has heck hoping he will!
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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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