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 want2lrn:


That will be enough of that ATHOME!


SmileyCentral.com
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Pilot Guy & StormwatcherCI - ty
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2444. Vero1

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 12 2010

GULF OF MEXICO...

WEAK SURFACE RIDGING COVERS THE MAJORITY OF THE GULF OF MEXICO
ANCHORED BY A 1018 MB HIGH IN THE CENTRAL GULF NEAR 27N88W
MAINTAINING FAIR CONDITIONS ACROSS MUCH OF THE AREA. THE SURFACE
RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE CENTERED OVER ERN
TEXAS MAINTAINING NE-E FLOW ALOFT ACROSS THE BASIN ACCOMPANIED
BY DRY AIR. HOWEVER...A FRONTAL BOUNDARY ACROSS THE NRN GULF
EXTENDING FROM THE NRN FLORIDA PANHANDLE TO ACROSS SRN LOUISIANA
IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS S OF THE FRONT TO
29N E OF 96W. A FEW ISOLATED STRONG STORMS ARE ALSO ACROSS THE
FLORIDA PENINSULA DUE TO SEABREEZE CONVERGENCE. A WEAK SURFACE
TROUGH IS IN THE SRN BAY OF CAMPECHE ALONG 21N95W TO 16N94W
SUPPORTING A FEW ISOLATED SHOWERS/THUNDERSTORMS ACROSS SRN
MEXICO. AN AREA OF ENHANCED MOISTURE PREVIOUSLY ASSOCIATED WITH
A SURFACE TROUGH IN THE WRN CARIBBEAN HAS MOVED ACROSS THE
YUCATAN PENINSULA AND S OF GUATEMALA IN THE E PACIFIC HELPING TO
GENERATE SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN
PENINSULA. DAYTIME HEATING AND INSTABILITY ARE ALSO SUPPORTING
SCATTERED SHOWERS/THUNDERSTORMS ACROSS WRN CUBA AND TO THE N
OVER THE SE GULF OF MEXICO. EXPECT SHOWERS/THUNDERSTORMS TO
CONTINUE ACROSS THE NRN GULF AS THE FRONTAL BOUNDARY DRIFTS
SWD.

CARIBBEAN SEA...
DAYTIME HEATING AND INSTABILITY ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS ACROSS WRN CUBA AND THE IMMEDIATE COASTAL
WATERS. THE REMAINDER OF THE NW CARIBBEAN IS UNDER THE INFLUENCE
OF DRY AIR ALOFT KEEPING CONDITIONS FAIR. A BROAD AREA OF LOW
PRESSURE CENTERED AROUND A 1007 MB LOW S OF HAITI NEAR 16N72W IS
IMPACTING MUCH OF THE CENTRAL CARIBBEAN. SEE SPECIAL FEATURES
ABOVE FOR MORE DETAILS. THE FAR ERN CARIBBEAN IS ALSO UNDER THE
INFLUENCE OF DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE CENTERED
OVER HISPANIOLA MAINTAINING FAIR CONDITIONS. EXPECT CONTINUED
SHOWER/THUNDERSTORM ACTIVITY ACROSS THE CENTRAL CARIBBEAN AND
INTO THE WRN CARIBBEAN AS THE LOW PRESSURE SYSTEM MOVES WWD.
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Quoting xcool:
no cat5 yet

But it must be pretty close.
Member Since: July 7, 2010 Posts: 0 Comments: 5628
2442. mbjjm
only noteworthy data from Hurricane Hunters in 92L is a pressure of 1006.4mb,highest winds around 28kts.
Member Since: August 23, 2010 Posts: 0 Comments: 310
2441. JLPR2
Quoting sunlinepr:
Notice that small cloud area at 58W 20N, still moving west.... It seems Igor should reach this area until it begings feeling the trough. Meanwhile it keeps loyal to 17-18N....



It is supposed to keep moving west till 49-50W

*Though you have a point with the little cloud.
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Houston

DURING THE MIDDLE AND LATE
WEEK PERIOD...THE RIDGE WILL DRIFT OVERHEAD AND THEN EAST OF THE
AREA.
BY THE END OF THE WEEK THE GFS AND ECMWF DIFFER ON THE
DEVELOPMENT AND MOVEMENT OF A POSSIBLE TROPICAL CYCLONE ACTIVITY
OVER THE SOUTHERN GULF OF MEXICO.

Hate when that happens.
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Quoting SSideBrac:
Just got back on - is there a Hurricane Hunter currently "examining" 92L?
NOAA Research Mission
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Quoting weatherwart:
I don't like this CMC run. No weakness in that high. Turns Igor west. I know it's too far out, but still... I like chocolate ice cream much better than this model run.

Link


Ukmet was doing that last night. Those kind of things don't give you warm fuzzies...
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To get a little perspective...

Unless Igor gets much slower or Julia gets much faster, I don't see a serious interaction here... or even down the road... what do u guys think?
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2435. Hhunter
30% chance lol..you guys are funny

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with the warm untapped waters of the NW Caribbean, I see no reason why 92L could not still develop.

It just has not done so yet, does not mean it will not
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Quoting AtHomeInTX:


Wow. I just looked on the 850 vort of that run. CMC brings 92L much farther north. Corpus Christi looks like? Thugh not strongly developed. Link


That will be enough of that ATHOME!
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Notice that small cloud area at 58W 20N, still moving west.... It seems Igor should reach this area until it begings feeling the trough. Meanwhile it keeps loyal to 17-18N....

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Quoting Seastep:
Sorry, look at visible.


Visible of Igor?
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2429. xcool
no cat5 yet
Member Since: September 26, 2009 Posts: 2 Comments: 15620
2428. Vero1
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 12 2010

ATLANTIC OCEAN...
A DEEP LAYER TROUGH EXTENDS DOWN THE ERN UNITED STATES SEABOARD
SUPPORTING A FRONTAL BOUNDARY THAT EXTENDS ACROSS NRN FLORIDA
AND ALONG THE NRN GULF OF MEXICO. SCATTERED
SHOWERS/THUNDERSTORMS ARE S OF THE FRONT FROM 29N-31N W OF 76W.
A SECOND DEEP LAYER TROUGH IS TO THE E ALONG 55W SUPPORTING A
SECOND FRONTAL BOUNDARY ENTERING THE DISCUSSION AREA NEAR 32N55W
TO 28N67W. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 45 NM
EITHER SIDE OF THE FRONT. SHOWERS/THUNDERSTORMS ARE ALSO N OF
HISPANIOLA APPROACHING TURKS AND CAICOS ASSOCIATED WITH THE
BROAD AREA OF LOW PRESSURE IN THE CENTRAL CARIBBEAN. THE
REMAINDER OF THE SW ATLC IS UNDER THE INFLUENCE OF DRY AIR
AROUND AN UPPER LEVEL RIDGE CENTERED NEAR 27N71W. FARTHER E...A
WEAK SURFACE TROUGH EXTENDS FROM 22N57W TO 18N56W SUPPORTING A
FEW ISOLATED SHOWERS/THUNDERSTORMS WITHIN 90 NM W OF THE AXIS.
MAJOR HURRICANE IGOR IS DUE E. SEE SPECIAL FEATURES ABOVE. THE
REMAINDER OF THE ERN ATLC IS DOMINATED BY SURFACE RIDGING
ANCHORED BY A 1033 MB HIGH CENTERED N OF THE AZORES ISLANDS.
ALOFT...AN UPPER LEVEL RIDGE IS N OF IGOR WITH AN UPPER LEVEL
TROUGH COVERING THE ERN ATLC CENTERED BETWEEN THE AZORES ISLANDS
AND THE CANARY ISLANDS.
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2427. bird72
Levi, can you answer my post 2313, thanks.
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Why can't they issue another Special Advisory? Igor is definitely looking like a Category 5 Hurricane.
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Just got back on - is there a Hurricane Hunter currently "examining" 92L?
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By the way, whoever posted the image of the wave over the interior of Africa that was perhaps the healthiest, most impressive wave I've ever seen. I am eagerly awaiting what it will look like once it enters the Atlantic.
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2010SEP12 234500 6.7 931.4/ +2.0 /132.2 6.7 6.9 6.9 NO LIMIT OFF OFF 16.04 -71.61 EYE 24 IR 17.67 47.10 COMBO
Member Since: September 2, 2009 Posts: 130 Comments: 21091
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With 92L I'm starting to think more of a Hermine-type development, if anything at all... just not quite pulling together right now.
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2419. xcool
no west wind 92l
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting AtHomeInTX:


Hey Tex. Just getting caught up today. Haven't taken a good look at 92L yet. Still trying to get past the WOW factor of Igor. Hope he stays out to sea.


Hey AtHome. :)
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2417. Seastep
Sorry, look at visible.
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2414. BDAwx
I don't see any north motion at all, in fact there may have been a very slight wobble just south of west for a time, but a westward motion has definitely resumed if that was the case.
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Still too much of a southern "tail" on Igor to qualify as completely annular, IMO.
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Quoting stormwatcherCI:
235230 1529N 07316W 7110 03016 0068 118 062 174008 008 /// /// 03


Pressure 1006.8 ?
There isn't a surface circulation whatsoever. It's just an open wave consisting of a large area of 1007-1006mb pressures. To put it in perspective, they've been finding that pressure for about 20-30 minutes straight.

I still think it'll develop, but not in the near-future.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2411. dmaddox
it's set on just South of 18 degrees North for awhile IMO...
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2410. xcool
angiest .further west i think about 75w jmo
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting weatherman12345:

that was a clue Levi pointed out


Yep. Saw that. Hopefully Igor will still stay out to sea though cuz WOW! I'm glad 92Ls percentage went down
Still not convinced it will not develop. Just another thing to watch.
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Quoting btwntx08:
watch stewart do the unthinkable again
Meaning what, exactly....

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2407. bird72
Quoting angiest:


Second time in a week or so they have had advisories (Igor resulted in a watch).

I think in history also.
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the potential for development of 92L is definitely still there

conditions are favorable for development and pressures are low in the area, it just has to find a way to put it all together
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2404. dmaddox
im outta here for a bit...
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2403. Seastep
Forget annular, imo. Look at 22:45 frame. Still there on 23:15, really.

Start seeing geometric shapes in the eye and it's just flat out strong.

Edit: Sorry, look at visible.
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2401. angiest
Quoting xcool:


Not looking like north any time soon.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting MiamiHurricanes09:
Why?
235230 1529N 07316W 7110 03016 0068 +118 +062 174008 008 /// /// 03


Pressure 1006.8 ?
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Quoting sunlinepr:


As Jeff Masters has quoted all this season, all around Global Warming records have been established this year. And that can be noticed in the ammount of Water Vapor in the ITCZ this year.....


Not so much. Global temperatures were indeed warmer with many records, but really only over land masses, not the oceans. Joe Bastardi explains this well too....
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Quoting FatPenguin:


Record temps in the MDR????


Record temps or even record temps for a season does not and cannot be directly attributed to climate change. Those are meteorological phenomena.

Back to the tropics.
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2397. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15620
2396. 7544
igor like keep going west to much
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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.