Potentially dangerous 92L steadily developing; Igor nears hurricane strength

By: Dr. Jeff Masters , 3:04 PM GMT on September 11, 2010

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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

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Blog Update
Puerto Rico tropical forecast
Hurricane Igor and Tropical Storm Julia ?
Link
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Quoting want2lrn:


I guess where i am getting stuck, is i am taking the arrows on that map to be gospel for the way the storm should move. I just need to hit google pretty hard to figure all this out lol


Yes, there can sometimes be discrepancies in the CIMSS steering maps, when you compare them to water vapor imagery.

However, most of the time it's accurate. What you really need to do when using these steering layers, is view the steering currents from at least 12 hours back to present. That way, you will be able to tell the evolution of the steering flow over a longer period, making your forecasts more accurate.
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Comrade Igor is firing some very deep convection.

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1570. Patrap
Quoting KimberlyB:


Thanks much Pat!!

Lookin' a little wobbly, no? Or is it just me? (which is 100% possible lol)


Dats what dey do..they never follow a straight line as the forces involed make um wobble.

Kinda like us blogger types.

So expect the wobble-itis to increase as Igor trends west thru time.
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1569. Patrap

00z Igor Early Cycle NHC model tracks
Igor Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)




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Great choice by the NHC to upgrade to 90% now future TD12, or known as right now 93L.
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A NASA page about lightning and hurricanes: http://www.nasa.gov/centers/goddard/news/topstory/2007/lightning_hurricane.html

Do note that this entire discussion is only about lightning around the eyewall. Beyond that, is irrelevant.
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Quoting Patrap:
Igor
Floater - Rainbow Color Infrared Loop


TFP's are available,click the Box marked Trop Pts.


Thanks much Pat!!

Lookin' a little wobbly, no? Or is it just me? (which is 100% possible lol)
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Quoting KoritheMan:


One should always use water vapor imagery in conjunction with the CIMSS maps to get a clearer picture. Right now, WV loops are not indicating anything that would push the system SW.


I guess where i am getting stuck, is i am taking the arrows on that map to be gospel for the way the storm should move. I just need to hit google pretty hard to figure all this out lol
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Quoting TheDawnAwakening:
I agree with the 90% upgrade for 93L. Should see TD12 by 5am AST update. Not surprised. This is the next TS.

Kori, what do you disagree with, in terms of my track for 92L? Too far south of Jamaica, or too far north afterwards?


The former.
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WOW, Igor is going through a quick period of ramping up now, impressive convection over within the CDO and a great equatorward outflow channel developing nicely.
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If Igor continues on the w to wnw track, I don't see how the EC will dodge this monster storm. I keep hearing curvature but the NHC mentions nothing about it. I would think by the end of the forecast, which would be next week.The NHC should have a better handle on Igor. Its hard to concentrate on 92L & 93L.
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1561. help4u
Julia will follow Igor out to sea.
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1560. JLPR2
I knew the avalanche of special two's were coming. XD

Just post the updated piece guys, we all got access to the NHC site. :|
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how many times is the special TWO going to be posted? lol
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
1557. Patrap
Igor
Floater - Rainbow Color Infrared Loop


TFP's are available,click the Box marked Trop Pts.
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1556. SLU
000
ABNT20 KNHC 120319
TWOAT
SPECIAL TROPICAL WEATHER OUTLOOK...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1120 PM EDT SAT SEP 11 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SPECIAL OUTLOOK ISSUED TO RAISE DEVELOPMENT CHANCE FOR SYSTEM IN THE
EASTERN ATLANTIC AND TO INDICATE IGOR AS A HURRICANE NOT A TROPICAL
STORM

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON RECENTLY
UPGRADED HURRICANE IGOR...LOCATED ABOUT 1140 MILES WEST OF THE CAPE
VERDE ISLANDS.

SHOWERS AND THUNDERSTORMS HAVE DECREASED IN ASSOCIATION WITH A
BROAD AREA OF LOW PRESSURE LOCATED OVER THE EAST-CENTRAL CARIBBEAN
SEA. HOWEVER...ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR
DEVELOPMENT OF THIS SYSTEM...AND A TROPICAL DEPRESSION COULD FORM
DURING THE NEXT COUPLE OF DAYS AS IT MOVES WESTWARD INTO THE
CENTRAL AND WESTERN CARIBBEAN SEA. THERE IS A HIGH CHANCE...60
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL
IS POSSIBLE IN THE NORTHERN LEEWARD ISLANDS...PUERTO RICO...THE
VIRGIN ISLANDS...AND HISPANIOLA DURING THE NEXT DAY OR SO. THESE
RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES...ESPECIALLY IN MOUNTAINOUS TERRAIN.

SATELLITE PICTURES INDICATE THAT THE VIGOROUS TROPICAL WAVE AND
ASSOCIATED LOW PRESSURE SYSTEM ABOUT 375 MILES EAST-SOUTHEAST OF
THE CAPE VERDE ISLANDS IS BECOMING BETTER ORGANIZED. IF CURRENT
TRENDS CONTINUE...ADVISORIES COULD BE INITIATED TONIGHT OR SUNDAY.
INTERESTS IN THE CAPE VERDE ISLANDS SHOULD CLOSELY MONITOR THE
PROGRESS OF THIS SYSTEM IN CASE WATCHES OR WATCHES ARE REQUIRED.
THERE IS A HIGH CHANCE...90 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY
WESTWARD AT 10 TO 15 MPH.

SHOWERS ACTIVITY HAS DEVELOPED IN ASSOCIATION WITH A WEAK LOW
PRESSURE SYSTEM LOCATED ABOUT 900 MILES EAST OF BERMUDA.
DEVELOPMENT OF THIS SYSTEM APPEARS UNLIKELY BEFORE IT IS ABSORBED
BY A FRONTAL SYSTEM. THERE IS A LOW CHANCE...10 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER KIMBERLAIN/BEVEN



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I agree with the 90% upgrade for 93L. Should see TD12 by 5am AST update. Not surprised. This is the next TS.

Kori, what do you disagree with, in terms of my track for 92L? Too far south of Jamaica, or too far north afterwards?
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Quoting earthlydragonfly:
taken tonight



it will be on local channel 2 in orlando on Monday


WOW! Great Pic!!
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Quoting pottery:

AAAaacckkk!!
Please disregard my previous post.
I misread your question entirely!!

I think I better go to bed...


I understand...been looking at WU and football all day, bout ready myself!
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Quoting PSLFLCaneVet:
I wish that someone could tell me why the connection between lightning and intensity is made. I've heard this before but, after being in multiple "eyes", I have never observed it.
A quick google answer: http://wattsupwiththat.com/2009/06/07/a-new-study-on-predicting-maximum-hurricane-intensity-using-l ightning/
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Quoting want2lrn:
YESSSSS...i did take my first step. So as i see that map in post 1462. Why does it not indicate a SW move for 92L?


One should always use water vapor imagery in conjunction with the CIMSS maps to get a clearer picture. Right now, WV loops are not indicating anything that would push the system SW.
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Quoting earthlydragonfly:
taken tonight



it will be on local channel 2 in orlando on Monday
Very nice shot. Was that a long exposure? Kudos.
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Quoting pottery:

AAAaacckkk!!
Please disregard my previous post.
I misread your question entirely!!

I think I better go to bed...


LOL hello Mr. Pottery
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1548. Relix
Julia... really will she go north? Hmm...

I know Igor is out of the ballpark for us here in the islands so I am looking at the next threat =P
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1547. help4u
btwtnx can you draw me a picture of what you are trying to say?
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Quoting clwstmchasr:
Drake - What happened to our Noles??????
UGH


None of the Florida teams did very well today!!
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1545. beell
Before you and Drak pummel me into submission EDIT: NOT, lol-gotta get in a "best wishes and good luck" as you dive into your college studies.

Drak, Levi, just a cool thing for both of you (and many others, of course)
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1544. pottery
Quoting want2lrn:


DAMNIT....i thought i had just taken my first baby step

AAAaacckkk!!
Please disregard my previous post.
I misread your question entirely!!

I think I better go to bed...
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Quoting Stormchaser2007:
Here she comes....




SATELLITE PICTURES INDICATE THAT THE VIGOROUS TROPICAL WAVE AND
ASSOCIATED LOW PRESSURE SYSTEM ABOUT 375 MILES EAST-SOUTHEAST OF
THE CAPE VERDE ISLANDS IS BECOMING BETTER ORGANIZED. IF CURRENT
TRENDS CONTINUE...ADVISORIES COULD BE INITIATED TONIGHT OR SUNDAY.
INTERESTS IN THE CAPE VERDE ISLANDS SHOULD CLOSELY MONITOR THE
PROGRESS OF THIS SYSTEM IN CASE WATCHES OR WATCHES ARE REQUIRED.

THERE IS A HIGH CHANCE...90 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY
WESTWARD AT 10 TO 15 MPH.


That picture will give me nightmares...lol
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CI# /Pressure/ Vmax
4.3 / 982.2mb/ 72.2kt


Final T# Adj T# Raw T#
4.2 4.6 5.8
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Quoting PcolaDan:


Okay, the double (triple?) negative thing has me confused. Lightning indicates strengthening or not strengthening? (Brain dead, football all day)
I wish that someone could tell me why the connection between lightning and intensity is made. I've heard this before but, after being in multiple "eyes", I have never observed it.
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YESSSSS...i did take my first step. So as i see that map in post 1462. Why does it not indicate a SW move for 92L?
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Quoting atmoaggie:
Lightning would strongly indicate strengthening in the next day. But, for Igor, the lack of it means little.


Thanks.
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Quoting earthlydragonfly:
taken tonight



it will be on local channel 2 in orlando on Monday


Unearthly! :)
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Quoting help4u:
with the next couple cape verde systems curving way out to sea,and the high pushing anything south into mexico and troughs coming one after the other on east coast could the threat of anything hitting US about over.
wrong
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Quoting earthlydragonfly:
taken tonight



it will be on local channel 2 in orlando on Monday


Stunning!
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Quoting pottery:

I dont think this is correct.
But it is a wonderful concept.


DAMNIT....i thought i had just taken my first baby step
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taken tonight



it will be on local channel 2 in orlando on Monday
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Quoting want2lrn:


Ok. If i understand it correctly, take the pressure from the storm and find the corresponding layer and that map will give you the general steering of the storm?


Correct.
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Quoting PcolaDan:


Okay, the double (triple?) negative thing has me confused. Lightning indicates strengthening or not strengthening? (Brain dead, football all day)
Lightning would strongly indicate strengthening in the next day. But, for Igor, the lack of it means little.
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1525. pottery
Quoting want2lrn:


Ok. If i understand it correctly, take the pressure from the storm and find the corresponding layer and that map will give you the general steering of the storm?

I dont think this is correct.
But it is a wonderful concept.
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Special TWO just issued for 93L, up to 90%.
Member Since: July 8, 2005 Posts: 259 Comments: 24191

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.