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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What about growing in size?
Ummm what? wow those be big words to me... wow... can you show me a map.
You are right. I remember that now.
## ANNULAR HURRICANE INDEX (AHI) AL112010 IGOR 09/12/10 18 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=6 NFAIL=1 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
## ANNULAR INDEX RAN NORMALLY
You are just kidding, right?
## ANNULAR HURRICANE INDEX (AHI) AL112010 IGOR 09/12/10 18 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=6 NFAIL=1 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
## ANNULAR INDEX RAN NORMALLY
Exactly. Quoting Saffir-Simpson for CAT5:
"Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet above sea level and within 500 yards of the shoreline. "
Yeah guys, Igor is forming some pimples! Quit stressing him out! LOL!
6.3 / 942.2mb/122.2kt
(and, I see, no change from 12 to 18 UTC)
What will we get at 19N 80W?? TCHP there is easily 4 times what it is under Igor, the air has more moisture and the water is 2 degrees warmer. October in the NW Caribbean might be interesting/crazy.
Hey angiest! Should gradually grow larger, especially if/when Igor undergoes eyewall replacement cycles. That acne could get worse (/bad pun) and spread out Igor's convective deck.
I didn't think so, especially with that feeder band on the southeast quadrant.
Just curious, does anybody know if Andrew is considered to have been annular at landfall?
How big it's grown,
And all the while
We should have known,
It was to be.
there are some other verses, but I dont remember...
1.) Upper level conditions should remain favorable.
2.) SSTs are only going to get warmer.
3.) Heat content is going to get deeper.
TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 115 124 126 126 126 129 131 138 135 130 126 123 118
V (KT) LAND 115 124 126 126 126 129 131 138 135 130 126 123 118
V (KT) LGE mod 115 128 132 130 128 124 123 124 125 122 117 114 111
SHEAR (KT) 4 1 6 6 11 6 1 7 7 6 1 5 11
SHEAR ADJ (KT) -2 0 -3 -2 -1 0 0 -3 -1 -5 5 2 0
SHEAR DIR 28 112 135 81 73 26 341 10 242 284 79 224 188
SST (C) 28.1 28.2 28.3 28.4 28.5 28.7 28.9 29.1 29.1 29.1 29.1 29.1 29.0
POT. INT. (KT) 139 140 141 142 144 147 149 152 153 153 153 152 151
ADJ. POT. INT. 132 134 135 135 135 138 138 140 140 139 137 136 134
200 MB T (C) -51.7 -51.5 -51.4 -51.3 -49.7 -50.2 -49.3 -49.7 -48.9 -49.2 -48.3 -48.7 -47.7
TH_E DEV (C) 10 11 11 11 11 12 12 12 11 10 10 10 10
700-500 MB RH 63 61 58 57 56 54 55 53 53 57 53 51 50
GFS VTEX (KT) 23 25 26 30 30 34 32 37 38 40 40 42 43
850 MB ENV VOR 72 70 65 72 72 76 100 103 120 140 167 163 177
200 MB DIV 54 67 77 73 129 20 85 72 71 3 99 19 43
LAND (KM) 1564 1513 1462 1437 1364 1236 1174 1037 922 819 759 741 767
LAT (DEG N) 17.7 17.8 17.8 18.0 18.1 18.6 19.3 20.1 21.1 22.0 23.0 23.9 24.9
LONG(DEG W) 46.3 47.5 48.7 49.8 50.8 52.8 54.5 56.0 57.4 58.9 60.4 61.8 63.2
STM SPEED (KT) 11 11 11 10 10 9 8 8 9 8 8 8 8
HEAT CONTENT 41 43 48 54 62 69 70 82 70 65 56 63 53
Igor must be hitting puberty...
EWRC might be a good thing for eastern seaboard to cheer for and soonest.
Saw that too, but wobbles are common in big intensification episodes. Danielle and Earl wobbled a lot, but that didn't equate to any real changes in the forecast track.
Could one of the trough's miss recurving Igor but pass close enough to form an outflow channel?? Right now Igor's is mostly radial.
Puberty?
Guess he's not done yet becoming a proud Russian hurricane.
Hmmmmmm. About the size of Louisiana or S. Carolina?
...probably rapid intensification??!
Seems possible.
(well, and everywhere else, too.)
Nope, far too many bands under that CDO:
Not tall cloud tops??
Yes, that large trough just NW of Igor is supposed to pass just north of the storm, which would allow for such an outflow channel.
Viewing: 1101 - 1151
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