Potentially dangerous 92L steadily developing; Igor nears hurricane strength
A tropical disturbance (92L) over the Eastern Caribbean, a few hundred miles south of Puerto Rico, is steadily organizing and appears likely to develop into a tropical depression by tonight or Sunday morning. Satellite loops show an impressive and expanding region of heavy thunderstorms, with good spiral banding and respectable upper-level outflow on all sides. Long range radar out of Puerto Rico shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. However, the rain bands are becoming more intense and more organized. San Juan, Puerto Rico reported a heavy rain squall at 8:44 am this morning, and radar estimates suggest two inches of rain fell in this squall just southeast of San Juan. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are at near-record warmth, 30°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-northwest at 11 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 Mexico's Yucatan Peninsula on Wednesday. The HWRF model has a more northwesterly track, taking 92L over the Dominican Republic, Haiti, and Cuba, but this model has been trending too far north in its tracks. I expect 92L will follow a path south of the islands, bringing it near or just south of Jamaica on Monday, then into the Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches tonight through Monday morning; southern Haiti can expect similar rains Sunday through Monday, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba will probably escape 92L's heaviest rains in this scenario (Figure 2.)
Intensity forecast for 92L
I can't find any reason to doubt this will be a tropical storm by Sunday or Monday, and potentially a Category 1 or 2 hurricane by Wednesday, if 92L avoids passage over Hispaniola and Cuba. The SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and makes 92L a Category 1 hurricane by Monday night. 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. The first Air Force Hurricane Hunter mission into 92L is scheduled for Sunday afternoon, but there will be a research mission by the National Center for Atmospheric Research G-V jet today that will give us valuable information on 92L's large scale environment and potential for development.
Figure 2. Forecast rain amounts from 92L from the 2am EDT Saturday run of the GFDL model. This model predicts most of 92L's heaviest rains will miss Haiti, but will affect Jamaica, the Cayman Islands, and the Yucatan Peninsula. Image credit: Morris Bender, NOAA/GFDL.
Igor
Tropical Storm Igor is very close to hurricane strength, and appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is moderate, 15 - 20 knots, waters are warm, 28°C, and Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor will track west under the influence of a strong ridge of high pressure for the next three days, then turn more to the west-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 has a slight chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 10% 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 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model 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. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.
Elsewhere in the tropics
A new tropical wave (Invest 93L) emerged from the coast of Africa yesterday, and is already showing signs of organization. Most of the models predict 93L will develop into a tropical depression 2 - 4 days from now, and NHC is giving 93L a 30% chance of developing by Monday.
Next post
This may be my only post today; I'll have a new post Sunday morning.
Jeff Masters
Reader Comments
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Storm,
Your sense of humor matches those awesome glasses lol! JOKE
Evening!
Creg, so good to see you again, Been missing you around here during the "season".. hope all is well with you.
The John Hope rule is very simple but verifies time and time again. If a tropical system does not develop into a tropical depression before entering the Eastern caribbean it is unlikely to do so before reaching the Western Caribbean.
I once looked at 30 years of data to see how this verified and found that in all those years there were only 8 or 9 systems that beacme TDs in the Eastern Caribbean including half of them from lows on the tail end of late season cold fronts. That left us with about 4 or 5 systems that managed to become TDs in the Eastern Caribbean over a 3 decade period from Easterly waves.
I would say that is strong validation of the Rule.
a
it cant break through a High that is not eroded no matter how strong he is
RIP 92L
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POOF
lol.... :) all those different faces.
I have read that on here a many of times, Just never knew It was the John Hope rule!
I am a newbie here. I posted earlier and did not get an answer ( a statement, not a complaint!).
Would you do me a favour and look at post 518? Trying to learn and interested in what I am missing.
TIA
He checks in sometimes on a blog here or there... he checked in Foxx's blog not too long again and give us alittle update.
Since Paloma in Nov 2008 blew away his little Brac, he has been off line alot more than Pre-Palmoa....
plus been so busy the last 2 years rebuilding the island.
Is a slight trend west a significant change in the 18Z model run?
everyone have a good evening and I know I will check in first thing in the morning.
I was only 1 year old so I don't remember it.
He said if a storm doesn't develope by the time it reaches the eastern carribean, it won't until it reaches the western carribean. He was a NHC forecaster, IIRC.
Hey Tex! Lol. Yeah, gots millions of 'em. Including my nervous smile when talking about my comfy home. Don't want Mother Nature to think I'm getting cocky and need to move again. Lol. Did you see the video I linked from Lake Charles NWS? It explains a lot. Link
Omar was an October storm that had its genesis on the tail end of a cold front, not an easterly wave like 92L. Remember I said that half of the 8 or 9 I found to have formed in the eastern Caribbean were late season systems from cold fronts.
no fish on GFS 18Z
Do your parents recall what happened that day?
Was it really bad?
I don't understand why the models aren't calling for much out of 92L when conditions seem favorable. I know models are just models but they do make me frustrated some times when they show such different outcomes. No patience I guess. Lol.
Hi, I looked at your post. Without all the technical comparisons that would be required, it is easiest to appreciate that models have a very hard time with intensity forecasts before a system gets classified as a TD. The intensity spread can be very large and you may have seen several waves developed as powerful hurricanes this year by the models but they did not even go on to become TDs.
My rule of thumb is to ignore intensity forecasts until we have a classified tropical cyclone.
lol
Link
just watched it. Thanks.... :) Just need to keep an eye on the high. You would think it would break down sooner or later....
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm
----- Current Analysis -----
Date : 11 SEP 2010 Time : 214500 UTC
Lat : 17:24:15 N Lon : 41:24:08 W
CI# /Pressure/ Vmax
4.3 / 982.2mb/ 72.2kt
Final T# Adj T# Raw T#
4.3 4.3 3.1
Latitude bias adjustment to MSLP : +0.0mb
Center Temp : -46.7C Cloud Region Temp : -58.7C
Scene Type : UNIFORM CDO CLOUD REGION w/ MW EYE
Positioning Method : FORECAST INTERPOLATION
Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC
Tno/CI Rules : Constraint Limits : MW ON
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
I think she was the strongest ever in the gulf pressure wise. Or I could be wrong. :)
I was just reading back , been away for awhile and saw you directed the question to me, sorry I can't answer as I'm not as familiar with the various charts and graphs but if anyone can answer your question you have directed it to the right person now, Kman, if anyone can explain it to you he will in simple and understandable terms, sorry I couldn't be of any help.
Makes sense. Thanks
Lets just hope it holds strong when it needs to. A breakdown come about November would be nice. :) Not that's wishcasting folks! Lol.
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