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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From what I gather people misunderstand the Hebert Boxes. Whereas the Hope rule predicts behaviour of a storm, the Hebert Box shows where a storm came from.
Kman,
Is there a technical name for the John Hope rule?
Trying to google it TIA
what does this mean? a greater threat to the us?
It dropped 92L.
92L may still fire back up tonight.
stay tuned.
does this make a us hit more likely?
Nope, this run recurves east of Bermuda.. Though I am trying to explain why the ensembles are not in agreement, along with the EURO ensembles and some other model runs.
5 years since FL has been hit by a hurricane and has managed to escape a very active year so far.
That was on the 0Z but not on 12Z.
Link
384 hours out is a bit too far for me to get ready. Having said that, I do believe that if this season stays active October could get interesting.
Invest92
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
must be an old run the Last run dropped it and the new run hasnt gone that far yet
Big weakness shown in the ridge due to the forecasted deep trough. The high that builds behind that trough would likely serve as a blocker to any further westward motion by Igor and force him to take the line of least resistance to the NW just as Earl did. The danger would be in a weaker trough, much flatter and exiting to the NE quicker. The high would then build to the North of Igor instead of to the NW and steer Igor to the WNW instead of acting as a blocking high.
It will all turn on just how strong the trough turns out to be and how far South it digs as that will determine the size and duration of the weakness in the sub tropical ridge.
When will Igor become a hurricane?
A: Tonight
B: Tommorow Morning
C: Tommorow afternoon
D: Moday
Remember the Great Tampa Bay Hurricane of 1921 hit in Oct.
LGEM? 135kts?
I don't think so. His disciples call it that. LOL
Are you talking about Wilma? That was 5 years ago.
Having trouble finding it. Got the short version by any chance.
trof
Could not help a grin!
I assume you mean from Corpus Christy? If so, and if you have not seen it already, might be of interest to you concerning 92L. I haven't seen GFS develop it but could be wrong. Wouldn't be the first time. :) Link
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