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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Quoting btwntx08:

its 384 hrs from now not likely to happen


I know it can change. That has just been the pattern so far as it seems to be with 92L as well.
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1044. angiest
Most recent annular analysis:

## ANNULAR HURRICANE INDEX (AHI) AL112010 IGOR 09/12/10 12 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=6 NFAIL=1 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
## ANNULAR INDEX RAN NORMALLY
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting DestinJeff:
192:



That is from yesterdays 12z run, note the date and the date at 168 hours. Both say the 19th of September.

Big shift south. 168 hours 00z.


168 hours 12z.


Keep in mind, this is ONE model run of a particular model. Don't put much stock in it yet.
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Quoting NOVArules:
How come storms with scary names(Walter,Igor,Bob) tend to be strong?


The same reason storms without scary names tend to be strong; Camille, Katrina, and Wilma, for instance, all sound like the name of an elderly aunt.

Really, it's only in hindsight that storm names seem scary; I don't find anything particularly threatening about Bob or Walter...

Igor, however, is another story...
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1041. breald
Quoting largeeyes:


You guys are kicking our butts. Embarassing effort....


I was under the impression you guys had a good team...LOl J/K. The game isn't over yet.
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Quoting tropicfreak:



If you are talking about igor, its still staying due west.
Not on the model at 168 hours.
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1038. DDR
Quoting pottery:

LOL see my last post.

Got it,got 96mm(3.77 inches) in 1.5 hours or so,my river is angry right now,im hearing boulders crashing coming down.
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Quoting tropicaltank:
I think Camille was actually a"CAT 6"


You don't need a cat. 6 classification. Here's why. Because the cat. of a hurricane determines the destructive potential of its max. sustained winds in the eye wall on buildings. So, if cat. 5 causes total destruction, what's worse than total destruction? A cat. 6 would have to turn the earth into a black hole (LOL)!
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1036. IKE
Quoting DestinJeff:
192:



That's yesterdays 12Z run.
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Quoting MiamiHurricanes09:
It hasn't recurved. Moving WNW/NW so far, could still be a threat to OBX.


If you are talking about igor, its still staying due west.
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Hi Pottery,

Wonder if we will have anything to worry about the year. Rain just keeps us wet at the moment. Had 6 inches Wed-Fri last week
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1033. Max1023
Based on Igor's satellite presentation I think that he has developed an upper anticyclone over his center. Igor's outflow pattern is nearly perfect in all directions. The CDO looks better than Earl's did at his peak, and Earl probably briefly reached 130 knots.
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Quoting DestinJeff:
192:



Is that TD12 doing a Fujiwara with Igor?
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Quoting DestinJeff:
192:

That's from yesterday.
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Quoting tropicaltank:
I think Camille was actually a"CAT 6"


I always heard that the wind guage at the airport in Gulfport broke at 200 mph.
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All this talk about being confident on Igor recurving needs to stop. We don't know what is going to happen. A 50% chance Igor recurves and a 50% chance Igor threatens the USA.
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1026. angiest
Quoting TexasHurricane:



hmmmmm, let me guess. MX/S.TX?


Two runs have gone over the Yucatan into the BOC, one went over Cuba and looking like it might go to the west coast of Florida (like Charley) based on steering, and one run went through the northern Caribbean including over or skirting Hispaniola.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
This is where Igor's forecast track gets VERY VERY hard to forecast.

He's one of these storms that can form their own enviroment and move how they want. He already destroyed 1/3 troughs.
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Quoting Melagoo:


... Did Andrew and Kitrina make it to 175?


I think Katrina peaked at 175 mph, but Andrew was 160 mph.
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Quoting weatherman12345:

lol

It's that understated, dry humor that is sometimes the funniest!
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Quoting MiamiHurricanes09:
168 hours, moving WNW/NW. Very intense category 5 cyclone.



That ECMWF run seems way west...where does it compare to the first hit of west we saw last night?
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Member Since: June 9, 2007 Posts: 4 Comments: 15920
Quoting KanKunKid:


After watching Levi's synopisis (awesome) It really is not set in stone where he will go. It adds the element of suspense to the picture and I would venture to guess that more people will be watching the course of Igor than any hurricane we have seen for awhile.
Cheesecake optional.


Yeah, Levi was talking about Euro ensemble model spreads showing anywhere from northern Cuba to Atlantic Canada! If I drew a 7 day cone of uncertanty, this would be a really really really fat cone out in 7 days, LOL!
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Quoting hurricane23:
12z EURO has a pretty sharp recurve which is pretty much again the consensus right now.
It hasn't recurved. Moving WNW/NW so far, could still be a threat to OBX.
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Quoting MiamiHurricanes09:
168 hours, moving WNW/NW. Very intense category 5 cyclone.


Wow!
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the steering current from CIMMS both the middle and upper level steering show a continuious west track until 70W where there seems to be a moderate weakness in the ridge. i believe that Igor will be so strong that it will create it's own upper level enviroment and continue between west and west north west. the northern islands should watch this hurricane very closely
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Quoting breald:


I have pizza, wine, Patriots on TV and winning and tropical chatter on the weather underground. Life is good.

So a trough would guide hie but a ridge would block him?


You guys are kicking our butts. Embarassing effort....
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EURO looks like the CMC model run... wow
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Quoting donna1960ruled:
Clearly, we need more Cats. Cat 5 wont hold this one.
I think Camille was actually a"CAT 6"
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Quoting angiest:
Three straight runs and at least 4 in the last two days that GFS has deveoped this system at 2+ weeks.




hmmmmm, let me guess. MX/S.TX?
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168 hours, moving WNW/NW. Very intense category 5 cyclone.

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12z EURO has a pretty sharp recurve which is pretty much again the consensus right now.
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1008. IKE
You beat me to it Jeff....96.1 outside my window.
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1006. Melagoo
Quoting Bordonaro:

Camille, Wilma, Allen and Mitch are the only Atlantic Hurricanes that peaked at over 175MPH to the best of my knowledge.

In 1969 as Camille approached the MS coast an advisory estimated her winds at a WHOPPING 200MPH!!!!!


... Did Andrew and Kitrina make it to 175?
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1004. angiest
Three straight runs and at least 4 in the last two days that GFS has deveoped this system at 2+ weeks.

Member Since: August 26, 2006 Posts: 16 Comments: 4766
Oh wow, Category 4 Igor?!?! Last I looked he was a tropical storm!
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Earl was at his max of 120 knots for exactly one TWO (11:00 PM on 9/1). I think Igor will beat that, no?
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1001. Max1023
The MPI map is probably a little low in Igor's area, as he has already reached nearly 90% of his local MPI. This is almost impossible, either Igor will stay at the local MPI and slowly strengthen for the next few days or the MPI is actually closer to 910mb in his area.
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Euro is coming south on the latest run so far.
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How come storms with scary names(Walter,Igor,Bob) tend to be strong?
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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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