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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I can't see anything as extreme as you are describing, it does look like the small amount of shear that exists is coming from 350deg however it looks to be less than 10 knots. Also, that could be caused by the ridge to the north of Igor resisting outflow a bit better than the flat upper levels to the south. A ridge produces anticyclonic flow which fights off outflow, this is restricting it slightly to the north. Once Igor approaches the trough to its NW (a couple thousand miles to its NW) the outflow in that direction will improve. Also, bands that far out would be blown apart by the outflow from the Eyewall anyway.
Water is very wet? Uhm. lmfao! I'm sorry, that's just cracks me up.
Now I'm hungry! LOL
Good afternoon
92L is closing in on 75W which, as you may recall, is the longitude I have been saying would be the threshold for it to develop if it did so at all. It appears to be near 16 N and 73 W at this time.
yes but they would be blown apart from the south to the north, not from north to south, there is some light shear coming from the north choking it off a bit, which is why I think it might not hit CAT 5 strength just yet
How deep is that hole? If one were standing in the center of the eye and looked up how high would be be? It looks deep, real deep.
Thanks in advance
Kman nailed it! John Hope rule. I would give him kudos if he was here!
You popped up at the perfect timing lol!
see post 1960
The water shouldn't support a Cat 5 anyway, 28 degrees is usually not enough to even get you a high 4. The fact that Igor is almost certainly stronger than 125 knots suggests that what little shear that exists is having almost no effect on the cyclone. I didn't think it would get to 5 6 hours ago but it looks like one now.
92L starting to look more interesting...
Currently, the deepest convection could be inducing a surface circulation to form. Hard to tell underneath the clouds and no weather obs close enough to be sure.
Strong southerlies to the east of the deepest convection evident in the cumulus cloud streets. Looks like some northeasterlies just south of Haiti's south coast. No sign of any westerlies yet obviously.
that's what I thought with earl, but dry air and southerly shear stopped it from reaching CAT 5 strength, we'll see
About 15 Kilometers or 10 miles (ish). The colder the cloud tops the higher they go, some -85 degree tops go to 12 miles high.
2010SEP12 221500 6.6 934.2/ 2.0 /129.6 6.6 6.8 6.8 3.2T/18hr OFF OFF 16.74 -70.44 EYE 25 IR 17.66 46.79 COMBO
What's the JH rule, if you don't mind
Bad idea to tamper with nature, bad things will happen.
*wink wink*
The last few satellite frames show the system going from being oriented from the SW to the NE in an elogated disorganized fashion to being more "upright" in the middle with a developing ball of convection. There is also evidence of good rotation near 16 / 73.
It still has work to do but there are signs of a change in the structure towards some development occurring.
Earl had twice as much shear and a LOT more dry air, if you look on WV the dry air is being pushed back more than 3 degrees west of the CDO edge. Also, the airmass is not as dry as Earl fought off. Hurricanes this strong do not usually entrain dry air all the way to the core, there is too large of a moisture field surrounding them.
The hh's are on their way in so we should know soon.
TD 12 -> Julia
92L -> Karl, "K" storm
Wave behind TD12 -> Lauren
Compared to the storm's overall size, Igor's eye is pretty big.
Hi there, thanks. We still have to see if it can continue to improve but this is the area where things start coming together for systems that have struggled in the Eastern and Central Caribbean.
12 days...
360 hour frame says yes.
We'll likely have Julia at 8PM
223230 2021N 07327W 5263 05484 0290 -024 -048 076013 014 /// /// 03
Yeah, I read that earlier that they were headed out this afternoon. Apperently more eveningtime. Good to hear. Definitely will watch the data coming in!
Lauren? I think you mean Lisa...
hehehe ;-D Good thing too or the cats wouldnt like it!
I agree. With Igor, it seems it has outflows of clouds on the north and south sides are fairly short or non existent compared to most major hurricanes. Now, I could be looking at the wrong maps, but does this mean Igor might have a chance of being an annular type storm?
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