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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crapola
more of a hint a circulation than an earlier passLink
OVERNIGHT?
01L (Alex): 6.7825
03L (Bonnie): 0.3675
04L (Colin): 1.9450
06L (Danielle): 21.7950
07L (Earl): 27.7750
08L (Fiona): 2.9400
09L (Gaston): 0.3675
10L (Hermine): 1.2725
11L (Igor): 5.4150
-------------------------------------
Total: 68.66
I'm very skeptical of this recurvature. Those two trough are too far north to really get Igor north. I think the UKMET, CMC, and EURO has the right idea.Kudos for the NHC on keeping a left bias on this one.
I'm very confident that Igor will push us over 100.
Also, Igor looks better and better on Dvorak.
Really should have been "TD or not TD, that's the convection", but I thought that might be a little too punny.
Seriously? lol
you are not allowed to have that opinion, because that is west-casting lol
*sarcasm off*
There's been alot of people stating that Igor WILL recurve away from the US.. Even when some of the good models trended west today, amazing.
SLICK!!! But very effective!!!
Looking at the water vapor, it appears to me that Igor should start moving more west-northwest to northwest around 20N, 55W. I think Igor takes a NW turn do to the second trough, then as a ridge builds, Igor may steer WNW south of Bermuda. After that, It's up in the air what else could happen. Another trough may recurve it, that being the best scenario to look at right now, or a weak trough lifts it north along the East Coast.
The forecast for Igor believe it or not is actually a VERY complicated forecast. The two troughs appear to me to be too far north to really recurve it, the third one which is coming out of Canada in a few days is the one that is supposed to do it all the way. The question is when and where. I believe Igor will move south of Bermuda, then start turning north from there. Also where will the high be? If the high shifts east and strengthens, Igor will become a problem for the southeast. I'm really skeptical of it recurving "harmlessly" out to sea at this time. I need a few more days to see how far west Igor can make it before the turn occurs.
I am just tired of the fact that no one is ever allowed to put forth the opinion that a storm may go further west than the models or the NHC predicts without being called a wish-caster, west-caster or being called out for wanting a US threat.
With Earl people said they felt he would move further south and west, and those people were called out for being west-casters. In the end they were right and the storm came much closer to the US than originally forecasted. Most people who feel a system will go further west, show evidence to support their opinion and they are still called out.
Ditto.
SLIGHTLY SLOWER...WHILE THE OTHER REGIONAL AND GLOBAL MODELS
SUGGEST A MORE PRONOUNCED WEAKNESS WITH TIME IN THE MID- TO
UPPER-LEVEL RIDGE.
.BUT STILL TO THE LEFT OUT OF RESPECT TO THE RELIABLE ECMWF
MODEL.
thats the two worrying parts of the discussion to me
like andrew in 91
430 PM CDT SUN SEP 12 2010
.SYNOPSIS...A COLD FRONT WILL CLIP THE FAR N WATERS TONIGHT INTO
MON. A WEAK SURFACE TROUGH WILL LINGER OVER THE FAR SW GULF
THROUGH WED. A LOW PRES SYSTEM IN THE EASTERN CARIBBEAN JUST
SOUTH OF HAITI WILL MOVE INTO THE NW CARIBBEAN WED...POSSIBLY AS
A TROPICAL CYCLONE...INCREASING WINDS AND SEAS IN THE FAR
SOUTHERN GULF. THE SYSTEM IS FORECAST TO BE OVER THE YUCATAN
NEAR 20N90W THU MORNING AND MOVE NW TO NEAR 22N97W THROUGH LATE
FRI NIGHT.
Welcome to my world.. I mean, I'm not saying it won't recurve, but we need to state the possibilities here just incase Igor really doesn't recurve as expected. People need to be prepared just in case, we don't need any shockers..
Igor lived up to its name.
Hypnotizing Eye....
Given how close Earl came to recurving after making landfall on the US east coast, you would think people would be a little more open to seeing the risk.
Personally Reed, I enjoy reading your take on things
Indeed..
BETWEEN 55W AND 65W
530 PM EDT SUN SEP 12 2010
.SYNOPSIS...LOW PRESSURE NEAR 16N72W WILL MOVE TO NEAR 17N77W
MON AFTERNOON AND NEAR 18.5N82W TUE AFTERNOON. THERE IS A MEDIUM
CHANCE OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. HURRICANE IGOR EAST OF THE AREA CENTERED NEAR
17.7N46.9W IS FORECAST TO MOVE INTO THE TROPICAL N ATLC TUE
NIGHT AND WED AS A MAJOR HURRICANE...THEN MOVE NORTH OF THE AREA
THU.
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