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
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 — Blog Index
At the end of the season it may be deemed an unnamed subtopical system. It formed along the northern apex of the same easterly wave that spawned Igor and persisted with good rotation for several days, but was always too sheared to develop further.
ACE Quick Tutorial
And Bastardi's measure of a season by a maximum recorded pressure only is ridiculous. Of all the things to measure a season, that's one of the least accurate to make any informed statement.
1. SUSPECT AREA (CENTRAL CARIBBEAN)
FLIGHT ONE -- TEAL 70
A. 12/1800Z
B. AFXXX 01EEA INVEST
C. 12/1145Z
D. 15.5N 70.0W
E. 12/1700Z TO 12/2100Z
F. SFC TO 10,000 FT
Yes, But not by a lot track-wise.
bastardi predicted early earl going further west than nhc called for but never hyped a direct earl hit but side swipe..so he has gravitas already this season and in this situation
I for one did.And I predicted several months in advance that Igor will probaly be a long track powerful cape verde storm.
Ok, that's what I was thinking, just making sure.
Thanks, From what I read annular hurricanes do not lose intensity as quickly, and maintain strenght in adverse conditions. Suppose an annular hurricane took a similar path as Earl. Earl seemed to go from a CAT 4 to CAT2 in the blink of an eye. Is my understanding correct in that an annular storm would be able to hold on to the CAT4 as it brushed NE and headed for Canadian Maritines?
That would be scary. I was glad to read they are VERY RARE.
Igor continues to undergo rapid intensification.
It won't "pull" it back but if it weakens/blocks the ridge that is causing the trade winds which are pushing Igor west then Igor slows down.
Still firing deep convection.
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 12 SEP 2010 Time : 151500 UTC
Lat : 17:39:04 N Lon : 45:23:32 W
CI# /Pressure/ Vmax
5.9 / 952.4mb/112.4kt
Final T# Adj T# Raw T#
5.9 6.2 6.2
That's correct to an extent. Still not properly understood (considering its rarity, can't blame scientists for that). Annular eye formation isn't permanent as some seem to think, it just puts off eyewall replacement cycles a bit longer. Eventually, it occurs though, and the hurricane returns to its default.
Annular eye formation is also only created when a storm attains 90% or more (approximately) of its MPI (maximum potential intensity).
Annular hurricanes typically do not survive in sea temperatures lower than 25C (77F). Earl very nearly became annular but developed outer bands. Igor has a better chance of doing so out in the Atlantic and seems to be wobbling AND developing a large eye.
Here's the list of favourable conditions for annular hurricanes again:
*An intensity 85% or greater from their theoretical maximum potential intensity,
*Weak wind shear from the east or southeast,
*A cold east wind at a high altitude (the 200 mbar pressure level),
*Near-constant sea surface temperatures between 25.4 °C and 28.5 °C, and
*Lack of relative eddy flux convergence at the 200 mbar pressure level, relative to the storm.
Bye,Bye Igor! Say hi to Iceland!
Wow, he was a Cat1 in the morning. Definite RI.
So what do I win? (j/k)
About Igor's ACE, his KE on the probability distribution is right at the same for SS scale.
We'll see what 18Z shows with Igor's strengthening.
Not that I'm against it - but a more scientific approach, suggested off season, might get me to take him more seriously.
re: 302, Progster, thanks for the follow-up on that yellow circle. I have to admit I wasn't following that wave once we got a TS off it. I'll be watching post season for a potential reclassification.
He's going nuts!!!!!!!
O_O
*Starts to hyperventilate*
Not very surprising though.
As usual, ADT goes through the roof as soon as it sees an eye. You can see the figures - particularly raw T# - go up in a shot as soon as the eye is seen.
That said, this is probably a Category 3 at the moment.
Viewing: 301 - 351
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 — Blog Index