92L still a threat to develop; Igor a hurricane; TD 12 forming near Africa
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
Reader Comments
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000
ABNT20 KNHC 122351
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN SEP 12 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...
THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
IGOR...LOCATED ABOUT 1065 MILES EAST OF THE NORTHERN LEEWARD
ISLANDS...AND ON TROPICAL DEPRESSION TWELVE...LOCATED ABOUT 140
MILES SOUTHEAST OF THE SOUTHERNMOST CAPE VERDE ISLANDS.
AIRCRAFT DATA FROM NOAA AND NASA RESEARCH MISSIONS WITHIN THE AREA
OF DISTURBED WEATHER OVER THE CENTRAL CARIBBEAN SEA SUGGEST THAT
THE SYSTEM MAY NOT HAVE A WELL-DEFINED CENTER OF CIRCULATION.
HOWEVER...THE DISTURBANCE IS STILL PRODUCING A LARGE AND
DISORGANIZED AREA OF SHOWERS AND THUNDERSTORMS WHICH COULD CAUSE
LOCALLY HEAVY RAINFALL IN PORTIONS OF PUERTO RICO...HISPANIOLA...
JAMAICA...AND CUBA DURING THE NEXT DAY OR TWO. THESE RAINS COULD
CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...ESPECIALLY IN
MOUNTAINOUS TERRAIN. THERE IS A MEDIUM CHANCE...40 PERCENT...THAT
THIS SYSTEM COULD BECOME A TROPICAL CYCLONE DURING THE NEXT 48
HOURS AS IT MOVES WEST-NORTHWESTWARD AT 10 TO 15 MPH TOWARD THE
NORTHWESTERN CARIBBEAN SEA.
ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
PUBLIC ADVISORIES ON TROPICAL DEPRESSION TWELVE ARE ISSUED UNDER WMO
HEADER WTNT32 KNHC AND UNDER AWIPS HEADER MIATCPAT2.
FORECAST/ADVISORIES ARE ISSUED UNDER WMO HEADER WTNT22 KNHC AND
UNDER AWIPS HEADER MIATCMAT2.
$$
FORECASTER BERG
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE SOUTHERN CAPE VERDE ISLANDS...INCLUDING MAIO..SAO TIAGO...
FOGO...AND BRAVA
It really doesn't look impressive but the environment is becoming increasingly favorable for it to develop. The pressure is falling very slowly and convection is beginning to stay more consistent. Time will tell though
A category 2 hurricane can be annular. It' all depends.
Hurricane Epsilone (2005) was a category 1 and had a similur structure of an annular hurricane.
Another Gaston?
Second time in a week or so they have had advisories (Igor resulted in a watch).
Dropped to 40%
Sssshhhhhh !
Record temps in the MDR????
Live Recon data in Google Earth
Igor has an awsome sat appearance this evening thankfully were in an active trough pattern across the lower 48, and if you ask me it does not appear that we will see the kind of ridging this season that you need to send these storms anywhere other than between the uprights of Bermuda and the east coast--or even farther right. This year's pattern is quite a far cry from the stubborn and intractable ridging we saw across the basin in 2004 when two 'canes were shoved into Florida within just a couple of weeks.
Storm you have more dignity than I do.
Just because timing allowed for loopholes of escape to the North does not say that the overall ridging pattern does not and will not persist.
US models too far north, but Hatch- It patrol dead on.
So far, the government forecasts have been dead on with Igors path.. a bit slow on the speed and on the intensity but wow, this has got to be used for an adevertisement!
Now the fun starts though as I have the storm 200 miles south of their position at 2 pm friday. Oh well. So far, great job by the boys that serve the red, white and blue.
ciao for now ****
joe b
.LONG TERM /7 AM TUESDAY THROUGH SUNDAY/...500MB SUBTROPICAL RIDGE
ACROSS THE NORTHERN GULF COAST AND NORTHERN GULF OF MEXICO WILL
CONTINUE TO PROVIDE SUBSIDENCE ACROSS DEEP SOUTH TEXAS TUESDAY.
THE REST OF THE FORECAST PERIOD WILL DEPEND ON THE STRENGTH OF THE
RIDGE AND THE AREA OF DISTURBED WEATHER OVER THE CENTRAL CARIBBEAN
SEA MOVING INTO THE WESTERN CARIBBEAN SEA TUESDAY. WHETHER THE
BROAD AREA OF LOW PRESSURE DEVELOPS INTO A TROPICAL
CYCLONE...ABUNDANT TROPICAL MOISTURE SHOULD MOVE WESTWARD ACROSS
THE YUCATAN PENINSULA WEDNESDAY INTO THE BAY OF CAMECHE AND
SOUTHWEST GULF OF MEXICO THURSDAY. WILL CONTINUE TO MENTION A
SLIGHT CHANCE TO CHANCE OF SHOWERS AND THUNDERSTORMS TUESDAY INTO
WEDNESDAY MAINLY FOR SEABREEZE CONVECTION IN THE AFTERNOON. WILL
NOT MENTION RAIN CHANCES THURSDAY AS SOME SUBSIDENCE SHOULD
DEVELOP ACROSS THE NORTHWEST GULF OF MEXICO BEFORE A POSSIBLE
TROPICAL DEPRESSION OR STORM MOVES TOWARDS THE MEXICAN COAST
FRIDAY. ALL INTERESTS IN THE WESTERN GULF OF MEXICO SHOULD REMAIN
VIGILANT OF A TROPICAL SYSTEM DEVELOPING THE NEXT COUPLE OF DAYS AND
MOVING WESTWARD INTO THE AREA TOWARDS THE END OF THE WEEK. WILL GO
AHEAD AND MENTION AT LEAST A CHANCE OF RAIN FRIDAY INTO THE
WEEKEND WITH LOW TO MID LEVEL MOISTURE INCREASING ACROSS NORTHEAST
MEXICO AND DEEP SOUTH TX LATE THURSDAY INTO EARLY FRIDAY.
&&
7 AM TUESDAY THROUGH FRIDAY...LIGHT TO MODERATE EAST TO SOUTHEAST
WINDS SHOULD PREVAIL ACROSS THE WESTERN GULF OF MEXICO TUESDAY
INTO WEDNESDAY WITH HIGH PRESSURE ACROSS THE EASTERN UNITED
STATES AND LOW PRESSURE ACROSS THE SOUTH CENTRAL PLAINS. THE REST
OF THE MARINE FORECAST WILL BE DEPENDENT ON THE AREA OF DISTURBED
WEATHER ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE ACROSS THE
CENTRAL CARIBBEAN SEA. MOST OF THE MODELS BRING THIS FEATURE INTO
THE NORTHWEST CARIBBEAN WEDNESDAY. WILL CONTINUE TO MENTION LIGHT
TO MODERATE EAST WINDS ACROSS THE COASTAL WATERS THURSDAY INTO
FRIDAY WITH LOW SEAS BUT IF A TROPICAL DEPRESSION OR STORM
DEVELOPS ACROSS THE NORTHWEST CARIBBEAN SEA AND MOVES WESTWARD
INTO THE BAY OF CAMPECHE AND EXTREME SOUTHWEST GULF OF
MEXICO...A MORE NORTHEAST WIND COMPONENT MAY DEVELOP ACROSS THE
WESTERN GULF OF MEXICO AND WINDS AND SEAS WILL LIKELY BE HIGHER AS
THE PRESSURE GRADIENT INCREASES. IN ADDITION...CONVECTION WILL
LIKELY INCREASE ACROSS THE WESTERN GULF THURSDAY INTO FRIDAY AS
DEEP TROPICAL MOISTURE ACROSS THE BAY OF CAMPECHE MOVES NORTHWARD.
&&
Link
000
WTNT32 KNHC 122350
TCPAT2
BULLETIN
TROPICAL DEPRESSION TWELVE INTERMEDIATE ADVISORY NUMBER 2A
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010
800 PM AST SUN SEP 12 2010
...DEPRESSION NEAR TROPICAL STORM STRENGTH...RAINBANDS MOVING OVER
THE SOUTHERN CAPE VERDE ISLANDS...
SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...13.3N 23.0W
ABOUT 140 MI...225 KM SE OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...W OR 280 DEGREES AT 12 MPH...19 KM/HR
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES
Probably not.
And as DR Masters has also stated that the warm upper Atmosphere due to said Global warming was a reason for lack of instability.
Last comment on the subject:0)
excuse me?
Great video blog - awesome explanation
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.
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....
Pressure 1006.8 ?
Not looking like north any time soon.
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