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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Igor is gonna strike PR!!!!
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Quoting AtHomeInTX:
This where I started my evening with the blog eating my posts. How I got in trouble too. Lol. Night y'all. See ya tomorrow. :)


Night maam!!
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3744. RyanFSU
Julia never makes it past 30N in the ECMWF 00Z run, but gets stuck due to the binary interaction with Igor. What a crazy situation the NHC has to deal with...

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This where I started my evening with the blog eating my posts. How I got in trouble too. Lol. Night y'all. See ya tomorrow. :)
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Quoting xcool:
BYE ALL.


night bro!!
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3741. Legion
Quoting AtHomeInTX:
WOW! WAY too close for comfort!
Link


Looks like it's showing a possible Fujiwhara effect with Julia at the end of the run.
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birds eye view...EURO has wave coming off of africa

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3739. xcool
BYE ALL.
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SAN JUAN, PR DOPPLER RADAR
TS JEANNE MAKING LANDFALL
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ITS STILL MOVING WEST NEXT UPDATE THE MODELES COME DOWN TO THE SOUTH AND WEST LITTLE MORE.
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WOW! WAY too close for comfort!
Link
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COLD FRONT WILL ENTER THE FAR NW PORTION OF THE ATLC LATER
TODAY. WINDS WILL SHIFT TO THE NE BEHIND THE FRONT BUT WILL
REMAIN LIGHT. A BELT OF ELY WINDS IN THE 10 TO 15 KT RANGE WILL
PERSIST S OF 25N WITH SEAS OF 4 TO 5 FT E OF THE BAHAMAS. WINDS
AND SEAS WILL GRADUALLY INCREASE OVER THE E PORTION OF THE AREA
LATE IN THE FORECAST PERIOD THU AS MAJOR HURRICANE IGOR PASS TO
THE E OF THE AREA...HOWEVER TROPICAL STORM FORCE WINDS SHOULD
REMAIN E OF THE FORECAST REGION.

STRONG HURRICANE IGOR E OF THE AREA IS FORECAST TO APPROACH THE
NE TROPICAL N ATLC WATERS LATE TUE INTO WED AS A MAJOR
HURRICANE. SO A HURRICANE WARNING WILL BE HEADLINED N OF 18N E
OF 60W TUE NIGHT...AND HURRICANE CONDITIONS WILL CONTINUE
THROUGH WED THEN AS THE HURRICANE MOVES TO THE N OF THE AREA
TROPICAL STORM FORCE WINDS ARE EXPECTED TO LINGER N OF 20N E OF
60W INTO THU...WITH DECREASING WINDS AND SEAS FRI. OTHERWISE A
BROAD AREA OF LOW PRES IN THE CENTRAL CARIBBEAN LOCATED NEAR
16N73W WILL MOVE NW TO JUST S OF JAMAICA TONIGHT AND CONTINUE TO
MOVE ACROSS THE NW CARIBBEAN THROUGH EARLY THU THEN W OF THE
AREA THU NIGHT. THIS LOW COULD POSSIBLY DEVELOP INTO A TROPICAL
CYCLONE.

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3734. xcool
YEP MAYBE 94L
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tropical storm Jeanne over PR
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ARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT MON SEP 13 2010

MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA
AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W.

WEAK RIDGE DOMINATES THE GULF OF MEXICO WITH MAINLY E TO SE
WINDS OF AROUND 10 KT AND SEAS LESS THAN 3 FT. COLD FRONT WILL
CLIP THE FAR NE GULF TODAY. NE WINDS OF 10 TO 15 KT ARE
EXPECTED TO BLOW BEHIND THE FRONT. HIGH PRES IN THE WAKE OF THE
FRONT WILL MOVE FROM THE SOUTHERN U.S. PLAINS TO THE SE U.S.
WILL INCREASE WINDS TO 15 TO 20 KT OVER THE NE GULF TUE AND
ACROSS MOST OF THE EASTERN GULF WED AND THU THEN DECREASE ON
FRI. LOW PRES SYSTEM IN THE CENTRAL CARIBBEAN WILL MOVE INTO THE
NW CARIBBEAN LATE WED AND THU AND POSSIBLY DEVELOP INTO A
TROPICAL CYCLONE...INCREASING WINDS AND SEAS IN THE FAR SOUTHERN
GULF. THE LOW IS EXPECTED TO MOVE INTO THE BAY OF CAMPECHE FRI
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That's the one the gfs model keeps sending into GOM.
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Quoting xcool:
traumaboyy lmaooo
WOW INVEST 94L SOON.
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3729. Legion
Quoting jasoniscoolman2010x:
BY GOD LOOK HOW BIG INVEST 94L IS ON LAND...WOW..


I have a feeling that future Karl will be another monster.
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BY GOD LOOK HOW BIG INVEST 94L IS ON LAND...WOW..
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Awesome...SE TEXAS!!!
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3726. Vapors
Quoting CoopNTexas:
Phantom, Beaumont...my brother is a weatherman here.


Same here! I work out at Motiva but live in the west end of Beaumont...
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3724. xcool
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And you're out of blackout...

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Ok...Really going to bed, but thought this was odd. Still shows the current image when you click on an area...But look at the date.

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Quoting TexasHurricane:


oh wait, 3 years ago...must be Humberto.


Lol. Yeah. Hard to keep em all straight. Including Eduoard that was 4 in 3 years. Enough already!!! Lol.
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Rita 05, Ike 08
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3715. xcool
;
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Quoting AtHomeInTX:
this time 3 years ago...



This time 2 years ago...



How happy am I to be sitting snug in my bed right now!! :)


oh wait, 3 years ago...must be Humberto.
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Quoting TexasHurricane:
Nite all


Night Tex
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Link
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Nite all
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http://upload.wikimedia.org/wikipedia/commons/c/c4/Hurricane_Georges_(Puerto_Rico).PNG
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PSL...Have had the double quote thing happen to me before too. Think it might be an occasional glitch. Mail back at you.

Going to bed all. See everyone tomorrow.
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3706. RyanFSU
The "reliable" ECMWF really had a bad init as well. 984 mb at t=0 and then 983 mb at t=24 hours. It takes a full 72-hours before ECMWF ramps it up to 115 kts and 941 mb. Igor is a huge hurricane, but ECMWF sure is taking its sweet time getting there...
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Quoting CoopNTexas:
Phantom, Beaumont...my brother is a weatherman here.
Hello neighbor
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Quoting txsweetpea:

What are ya'll "yelling" and "dooming" about????? Fill me in!


Sorry....just 0200L psychosis on my part I am sure......I can't speak for my friend in NOLA!!
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Quoting AtHomeInTX:
this time 3 years ago...



This time 2 years ago...



How happy am I to be sitting snug in my bed right now!! :)


awww yes,hurricane Rita.
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Good lord, going to be light soon enough here. Got to turn in. Best wishes, and Good Night all.
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Phantom, Beaumont...my brother is a weatherman here.
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LOOK AT THE MODELES HERE
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Quoting StormJunkie:
Why haven't they put the Goes 15 science test on Igor yet...Bummer.
Quoting StormJunkie:
Why haven't they put the Goes 15 science test on Igor yet...Bummer.
SJ, you have mail. Not sure where the double qoute came from. Sorry, all.
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3696. RyanFSU
GFDL goes east of Bermuda as well. Here's the mash-up of the inner-nest maximum wind speeds: I think people are calling it a fish storm, but I don't think there are that many fish in the central Atlantic (?)

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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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