TD #9 (Irene)

[vicocala]

Tropical Storm Irene Discussion Number 14

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Sun Aug 07 2005

 

A Few Patches Of Deep Convection Redeveloped Near The Center And In

A Small Band To The East And Southeast...but Overall The Cloud

Pattern Is Rather Paltry. Even Though Irene Does Not Look Much

Like A Tropical Storm On Satellite Images...a Quikscat Pass From

Around 2115 Utc Showed Some Uncontaminated 35 Kt Vectors In The

Circulation. Thus The Current Intensity Is Kept At 35 Kt. The

System Should Continue To Move Through An Environment Of

Northwesterly Shear And Dry Air For The Next Day Or Two.

Afterwards...assuming Irene Survives...it Will Encounter Warmer Sea

Surface Temperatures And...perhaps...more Favorable Upper-level

Conditions. Therefore Some Strengthening Is Forecast After 36

Hours. The Official Intensity Forecast Is In Good Agreement With

The Latest Ships Output.

 

Initial Motion For This Advisory Is 300/10. There Is Little Change

To The Synoptic Reasoning For The Track Forecast. Irene Is Being

Steered By The Flow To The Southwest Of A Mid-level Anticyclone. A

Gradual Turn To The Right...into A Weakness In The Subtropical

Ridge...is Expected To Begin In A Couple Of Days. The Official

Forecast Is Similar To The Previous One.

 

Forecaster Pasch

[vicocala]

Tropical Depression Irene Discussion Number 17

Nws Tpc/national Hurricane Center Miami Fl

5 Pm Edt Mon Aug 08 2005

 

Convection Has Persisted To The East Of The Low Level

Center This Afternoon... Often Emanating From The Center Itself.

However... The Low Level Center Remains Exposed Dvorak Intensity

Estimates Remain T2.0/30 Kt. Although It Is Possible That Tropical

Storm Force Winds Are Reaching The Surface In A Limited Area Within

The Sparse Convection... Irene Is Maintained As 30 Kt Depression

For This Advisory. The System Is Struggling To Reorganize Within A

Fairly Dry And Stable Environment With Moderate Vertical Shear.

These Conditions Should Be Slow To Change Along The Forecast

Track... And Accordingly The Ships Guidance Shows Gradual

Strengthening To 45 Kt By 60 Hours...continuing On To 62 Kt By 120

Hours. However... The Gfdl Dissipates The System Within A Couple

Of Days. The Official Forecast Will Compromise And Remain Similar

To The Previous Advisory... Showing Modest And Gradual

Strengthening.

 

When The Convection Redeveloped This Morning... The Low Level Center

Slowed Down In Response. Smoothing Through The Stop-and-go Motion

During The Past 12 Hours Or So Yields An Initial Motion Of 285/10.

The New Official Forecast Is Basically An Update Of The Previous

Advisory... And There Is A Little More Confidence In This Track Now

Since Some Of The Models That Were Eastern Outliers This Morning...

Such As The Ukmet And Nogaps... Have Shifted Westward.

Therefore... Models Are Coming Into Better Agreement That A System

Of Moderate Tropical Storm Strength Will Move West-northwestward

Along The Southern Periphery Of The Lower/mid Level Subtropical

Ridge. The Slow Motion Shown At The End Of The Official Forecast

Is Indicative Of The Great Uncertainty Late In The Period...when

The Spread In The Models Is Still Quite Significant.

 

Forecaster Knabb

[vicocala]

Tropical Depression Irene Discussion Number 18

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Mon Aug 08 2005

 

Irene Continues To Look Insignificant On Satellite Images...and

Shows No Indications Of Restrengthening Any Time Soon. The

Low-cloud Center Is Near The Western Edge Of A Small Area Of Deep

Convection...and There Are No Obvious Banding Features. The

Depression Is Being Sheared By Westerly Flow Associated With The

Mid-atlantic Upper-level Trough. Also...dropsonde Data From A

Saharan Air Layer Research Mission With The Noaa G-iv Jet Confirm

That Irene Is In An Environment Of Very Dry Mid- To Upper-

Tropospheric Air. As The Cyclone Moves Farther To The West-

Northwest Over The Next Couple Of Days...it Is Likely To Enter A

Weaker Wind Shear Environment Since The Upper Flow Is Expected To

Become More Southeasterly. Some Restrengthening Is Therefore Shown

In The Forecast.

 

Initial Motion Is 285/11. Irene Is Expected To Eventually Turn More

Northward Later In The Forecast Period...in Response To A Weakness

In The Subtropical Ridge Near Bermuda. However There Are

Significant Differences Of Opinion Among The Global Models As To

The Configuration Of The Subtropical Ridge Over The Western

Atlantic At Days 4-5. By That Time It Does Appear That The

Steering Currents Will Become Quite Weak...so The Forward Speed Is

Forecast To Slow Considerably Late In The Period. The Official

Forecast For This Advisory Is Similar To The Previous One Through

Day 3 And Shifted A Little To The East Afterwards...but Not As Far

East As The Dynamical Consensus.

 

Forecaster Pasch

[Sage]

Thanks Vicocala. Let's all keep our fingers crossed that Irene remains out to sea. I know our cruisers going to Bermuda are hoping she will avoid them as well.

[vicocala]

Sage,

 

 

The way they keep moving the track further west and is disheartening, especially as it seems to be getting close to threatening the US coast. I guess that is one of the things I find facinating, yet horrifying about tropical systems, is their behavior.

 

Anyway, here is the last report as of 11:00 AM:

 

TROPICAL DEPRESSION IRENE DISCUSSION NUMBER 20

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

11 AM EDT TUE AUG 09 2005

 

THERE CONTINUES TO BE DEEP CONVECTION ASSOCIATED WITH IRENE WITH THE

SYSTEM LOOKING BETTER THAN IT DID 6 HOURS AGO. WOULD PREFER TO SEE

A LITTLE MORE ORGANIZATION TO THE CONVECTION BEFORE UPGRADING IRENE

TO A TROPICAL STORM GIVEN DVORAK ESTIMATES OF 30 KTS.

 

IRENE IS CURRENTLY UNDER THE INFLUENCE OF NORTHWESTERLY FLOW AT

UPPER LEVELS WITH A TROF CURRENTLY IN PLACE TO THE NORTH AND EAST

OF THE SYSTEM. WITHIN THE NEXT 24 TO 36 HOURS...THE MOTION OF

IRENE WILL BRING IT FAR ENOUGH WEST TO BRING UNDER THE INFLUENCE OF

AN UPPER LEVEL ANTICYCLONE CENTERED NEAR 28N AND 64W. THIS SHOULD

ALLOW FOR AN ENVIRONMENT WITH LESS SHEAR. THE SYSTEM IS CURRENTLY

FORECAST TO REACH TROPICAL STORM STATUS AT 36HRS.

 

THE INITIAL MOTION IS 280/9. THE 0000 UTC ECMWF...NOGAPS AND UKMET

MODELS ARE ALL IN THE SAME BALLPARK WITH THE TRACK OF THIS SYSTEM

TAKING IT GENERALLY ON A WEST TO WEST-NORTHWESTERLY TRACK WITH TIME

WITH A SLIGHT WESTWARD TREND NOTED. THE GFS WAS QUITE THE OPPOSITE

SHOWING THE SYSTEM SHEARING APART AS IT TOOK A MORE NORTHERLY

TRACK. WILL LEAN STRONGLY TOWARDS THE FORMER SOLUTION AND FOR NOW

BE SOMEWHAT CONSERVATIVE WITH INTENSIFICATION GIVEN THE MODEL

DIFFERENCES. THE OFFICIAL TRACK TAKES THE SYSTEM ON A MORE

WESTERLY COURSE THAN THE PREVIOUS TRACK BASED ON THE AFOREMENTIONED

MODEL TREND.

 

FORECASTER KORTY

[vicocala]

Sage,

 

 

The way they keep moving the track further west and is disheartening, especially as it seems to be getting close to threatening the US coast. I guess that is one of the things I find facinating, yet horrifying about tropical systems, is their behavior.

 

Anyway, here is the last report as of 11:00 AM:

 

TROPICAL DEPRESSION IRENE DISCUSSION NUMBER 20

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

11 AM EDT TUE AUG 09 2005

 

THERE CONTINUES TO BE DEEP CONVECTION ASSOCIATED WITH IRENE WITH THE

SYSTEM LOOKING BETTER THAN IT DID 6 HOURS AGO. WOULD PREFER TO SEE

A LITTLE MORE ORGANIZATION TO THE CONVECTION BEFORE UPGRADING IRENE

TO A TROPICAL STORM GIVEN DVORAK ESTIMATES OF 30 KTS.

 

IRENE IS CURRENTLY UNDER THE INFLUENCE OF NORTHWESTERLY FLOW AT

UPPER LEVELS WITH A TROF CURRENTLY IN PLACE TO THE NORTH AND EAST

OF THE SYSTEM. WITHIN THE NEXT 24 TO 36 HOURS...THE MOTION OF

IRENE WILL BRING IT FAR ENOUGH WEST TO BRING UNDER THE INFLUENCE OF

AN UPPER LEVEL ANTICYCLONE CENTERED NEAR 28N AND 64W. THIS SHOULD

ALLOW FOR AN ENVIRONMENT WITH LESS SHEAR. THE SYSTEM IS CURRENTLY

FORECAST TO REACH TROPICAL STORM STATUS AT 36HRS.

 

THE INITIAL MOTION IS 280/9. THE 0000 UTC ECMWF...NOGAPS AND UKMET

MODELS ARE ALL IN THE SAME BALLPARK WITH THE TRACK OF THIS SYSTEM

TAKING IT GENERALLY ON A WEST TO WEST-NORTHWESTERLY TRACK WITH TIME

WITH A SLIGHT WESTWARD TREND NOTED. THE GFS WAS QUITE THE OPPOSITE

SHOWING THE SYSTEM SHEARING APART AS IT TOOK A MORE NORTHERLY

TRACK. WILL LEAN STRONGLY TOWARDS THE FORMER SOLUTION AND FOR NOW

BE SOMEWHAT CONSERVATIVE WITH INTENSIFICATION GIVEN THE MODEL

DIFFERENCES. THE OFFICIAL TRACK TAKES THE SYSTEM ON A MORE

WESTERLY COURSE THAN THE PREVIOUS TRACK BASED ON THE AFOREMENTIONED

MODEL TREND.

 

FORECASTER KORTY

[Sage]

Vicocala,

 

I know what you mean. These systems seem to have a mind of their own and like to keep us guessing as to what they will do next. I have also been keeping tabs on Irene at www:crownweather.com, and they too seem to think that it may brush the US coast if it doesn't make the turn. We can just be ready, and again, thank you for keeping us all posted and up to date with what the storms are doing.

[vicocala]

Tropical Depression Irene Discussion Number 23

Nws Tpc/national Hurricane Center Miami Fl

5 Am Edt Wed Aug 10 2005

 

There Is Little Or No Evidence That Irene Still Has A Closed

Circulation. As Noted In The Previous Discussion...last Night's

Quikscat Ambiguities Could Not Define A Center...and The Low Cloud

Lines In The Night-vis Imagery Also Suggest That Irene Is

Elongating And Likely Has Degenerated Into An Open Trough. If There

Is A Center...it Is Probably South Of The Current Advisory Position

In The Deep Convection South Of 22n. Given The Uncertainties

However...it Is Prudent To Wait For Visible Imagery Before

Dissipating Or Relocating The Cyclone. The Initial Intensity Is

Lowered To 25 Kt Based On The Most Recent Quikscat Data And The

Present Lack Of Organization Of The System. If Irene

Survives...the Upper-level Flow Pattern Is Still Expected To Become

Gradually More Favorable For Development...and The Ships Guidance

Continues To Forecast Strengthening. The Official Forecast...a

Blend Of The Ships And Gfdl Guidance...calls For Less Development

Than The Previous Advisory.

 

The Initial Motion Of This Disorganized System Is Hard To Determine

But My Best Estimate Is 270/10. A Mid-level High Is Centered Near

Bermuda To The Northwest Of Irene. The Gfdl...gfs...ukmet And

Nogaps Models Continue To Want To Take Irene To The West-northwest

And Then Northwest Late In The Forecast Period As They Slide This

High Eastward. The Simpler Bam Models Do Not Have The Northwest

Turn. Over The Past Few Days...the Global Models Have Had A

Significant Right Bias While The Bams Have Performed Relatively

Well. Given The Present Westward Motion And These Biases...the

Official Forecast Has Been Shifted A Little Westward...and Is A

Compromise Between The Fsu Superensemble And The Medium Bam.

 

Both The Track And Intensity Forecasts Are Very Low Confidence.

 

 

Forecaster Franklin

[vicocala]

Tropical Depression Irene Discussion Number 24

Nws Tpc/national Hurricane Center Miami Fl

11 Am Edt Wed Aug 10 2005

 

The Convective Cloud Pattern This Morning Has Improved Significantly

Compared To 24 Hours Ago. It Is Still Difficult...however...to

Determine An Exact Center Lcoation...especially In Conventional

Imagery. The Initial Position Is Based On Continuity...a 24-hour

Westward Motion...and Trmm And Microwave Satellite Data. A 0912z

Quikscat Pass Intimated That A Low-level Center Could Be Farther

South Near 21n...but I Prefer To Remain Farther North Near The

Better Defined Mid-level Circulation...which Also Allows For Some

Possible Redevelopment Farther North.

 

The Initial Motion Estimate Is 275/10...even Though The Longer Term

Motion Has Been 270/08. Global Model Guidance Has Consistently

Displayed A 20-30 Degree Right-of-track Bias The Past 48 Hours.

This Is Not Surprising Since The Models Have Kept Irene Weak Or

Have Even Dissipated It...all The While Mid-level Northerly Flow

Has Been Keeping The Cyclone Farther South On A More Westward

Track. Water Vapor Imagery And Satellite-derived Winds From

Uw-cimss Still Indicate A Large Mid- To Upper-level Anticyclone

Located From The Southeastern U.s. Eastward Across Bermuda With

Deep North To Northeasterly Mid-level Flow On The East Side

Undercutting The Improving Upper-level Outflow Pattern. So In The

Short Term...a More Westward Component Of Motion Is Probable...

Barring Any Northward Redevelopment Of The Low-level Center. By

Days 4-5...most Of The Global Models Create A Weakness In The

Subtropical Ridge Off The Southeastern U.s. Coast...with A High

Center Shifting Eastward To Near Bermuda. This Is Expected To Allow

Irene To Move Slowly Northwestward Around The Southwest Periphery

Of The High. The Official Forecast Is To The Left Of The Previous

Advisory And Is On The Extreme Left...or South ...side Of The Nhc

Model Guidance Envelope. If A Westward Motion Continues Today And

The Center Does Not Reform Farther North...then The Track Will Have

To Be Shifted Even More To The Left On The Next Advisory.

 

Upper-level Outflow Has Become Better Established Over The Past 12

Hours And It Is Expected To Continue To Improve For The Next 3 Days

Or So. However...the Aforementioned Mid-level Northerly Flow

Undercutting The Outflow Layer Is Producing Some Mid-level Shear...

As Well As Advecting Very Dry Air Into The System. The Warm

Sea-surface Temperatures And Improving Outflow Pattern Should Allow

For At Least Slow Intensification As Intermittent Bursts Of Deep

Convection Occur Near The Center. It Is Possible That Irene Could

Reach Hurricane Strength Before The End Of The Forecast Period.

 

Forecaster Stewart

[vicocala]

Tropical Storm Irene Discussion Number 26

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Wed Aug 10 2005

 

Irene's Cloud Pattern Has Become Slightly Better Organized This

Evening. A Convective Band Over The Eastern Portion Of The System

Wraps Nearly Halfway Around The Circulation. Dvorak Intensity

Estimates Are A Consensus 35 Kt From Tafb...sab...and Afwa. This

Supports Re-upgrading The Cyclone To Tropical Storm Status. The

Upper-tropospheric Outflow Is Becoming Better Defined Except To The

South Where It Is Being Impeded By An Upper-level Cyclone To The

Southwest Of The Storm. Water Vapor Imagery And Analyses From The

University Of Wisconsin Cimss Show That The Northerly Mid- To

Upper-level Flow That Had Been Disrupting The Tropical Cyclone Is

Abating And That Irene Is Moving Into An Area Of Decreasing

Vertical Shear. Strengthening Is Forecast...as In The Previous

Advisory. As Usual...the Forecast Wind Speeds In The 3 To 5 Day

Time Frame Have Considerable Uncertainty Owing To A Lack Of Skill

In Longer-range Tropical Cyclone Intensity Prediction.

 

Recent Center Fixes From Both Geostationary And Microwave Imagery

Are Somewhat To The North Of The Previous Track. However...for

Continuity's Sake...i Have Adjusted The Current Motion Only

Slightly To The Right...290/11. The Main Steering Feature That

Concerns Us Is A Mid-tropospheric Ridge That The Global Models Are

Forecasting To Build Near And Just East Of The U.s. Mid-atlantic

States In 3 To 5 Days. It Is Too Early To Determine Whether This

Ridge Will Drive Irene To The Southeast U.s. Coast. It Is Still

Possible That The Tropical Cyclone Will Be Able To Move More

Northward Into A Weakness In The Ridge...as Suggested By Some Of

The Track Guidance Such As The U.k. Met. Office Global Model And

The Latest Gfdl Run...or Move More Westward And Reach The Coast As

Shown By The Ecmwf And Gfdn. The Official Forecast Track Has Been

Shifted A Little To The Right Of The Previous One...but Is Still

Well To The Left Of The Dynamical Model Consensus. The Nhc

Forecast Track Is Also Very Similar To The Latest Fsu Superensemble

Track.

 

Forecaster Pasch

[Sage]

Vicocala,

 

It looks as Irene is getting better organized, and I just hope that she decides to take that turn. Thanks for keeping us updated.

[vicocala]

Tropical Storm Irene Discussion Number 30

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Thu Aug 11 2005

 

Over The Past Several Hours....there Has Not Been Much Change In The

Organization Of The Storm As Shown By Satellite Images. Irene

Continues To Have Some Banding Features Over Its Eastern

Semicircle...but The Cloud Tops Are Not Very Cold And The Deep

Convection Encompasses A Rather Small Area. Dvorak Intensity

Estimates From Tafb And Sab Are Unchanged From The Previous

Package...so The Current Intensity Estimate Remains At 45 Kt.

Upper-level Outflow Over The Southeastern Quadrant Is Weak But

Appears Well-defined Over The Remainder Of The Circulation.

According To The Global Models...irene Will Be Moving Through An

Environment Characterized By Anticyclonic Upper-level Flow And Weak

Vertical Shear Over The Forecast Period. The Official Intensity

Forecast Is A Blend Of The Ships...gfdl...gfdn...and The Fsu

Superensemble Guidance...all Of Which Show Irene Strengthening Into

A Hurricane During The Next Couple Of Days.

 

Locating The Storm Center Remains A Challenge...especially With

Infrared Imagery. Thus The Initial Motion Estimate...300/13...is

An Educated Guess. Nwp Models Show A 500 Mb High Building Near

Bermuda During The Next Day Or Two...and Then Retrograding Westward

Later In The Forecast Period. As Irene Approaches The Ridge...

Steering Currents Are Likely To Weaken...so The Tropical Cyclone

Will Likely Be Moving Very Slowly In 3 To 5 Days. Beyond 36

Hours...the Track Model Guidance Diverges Significantly. The Gfdl

And Gfdn Are Now Showing A More Westward Track And Are On The Left

Side Of The Dynamical Suite. The U.k. Met Office And Nogaps

Solutions Show A Northward Turn...as Does The Gfs. However The

Latter Model Essentially Dissipates The Tropical Cyclone By The End

Of The Period. The Official Forecast Is Fairly Similar To The

Previous One...and Also Shows Considerable Slowing Of The Forward

Speed By 72 Hours. This Is In Reasonable Agreement With The Latest

Fsu Superensemble Track.

 

Five-day Tropical Cyclone Forecasts Have Considerable Uncertainty In

Both Location And Intensity...so It Is Still Too Early To Talk

About Specific Threats To The East Coast Of The United States.

 

Forecaster Pasch

[vicocala]

Tropical Storm Irene Discussion Number 31

Nws Tpc/national Hurricane Center Miami Fl

5 Am Edt Fri Aug 12 2005

 

Microwave Imagery From The Windsat...dmsp...noaa...and Trmm

Satellites Between 2201z And 0335z Indicate That The Center Of

Irene Is A Little To The Northeast Of The Previous Advisory

Position. The Windsat And Trmm Data Showed A Well-defined

Low-level Center...and Conventional Infrared Imagery Shows

Increasing Convective Banding. Satellite Intensity Estimates Are

55 Kt From Afwa...and 45 Kt From Tafb And Sab. Based On The

Improved Satellite Signature...the Initial Intensity Is Increased

To 50 Kt.

 

The Initial Motion Is Now 310/13. Irene Is Between A Deep-layer

Ridge With A Center East Of Bermuda And An Upper-level Low Near

26n74w. A Deep-layer Weakness In The Ridge Exists Near 32n70w Due

To A Short-wave Trough Passing To The North. Irene Is Currently

Heading For The Weakness...which The Large-scale Models Forecast To

Fill Over The Next Five Days. The Big Question Is Will Irene

Recurve Through The Weakness Before It Fills. All Dynamical Model

Guidance Suggests The Storm Will Recurve Before Reaching The United

States Except For The Outlier Gfdn...which Calls For A Landfall In

North Carolina. The Official Forecast Compromises Between These

Extremes...calling For Irene To Turn North-northwestward After

48-72 Hr And Maintain That Motion Through 120 Hr. The Forecast

Track Calls For A Slight Left Turn During The First 36-48 Hr In

Anticipation Of Rising Pressures To The North Behind The Shortwave

Trough. Overall...the Forecast Track Is Shifted To The East Of The

Previous Track....and Is Along The Left Edge Of The Main Envelope

Of Guidance.

 

Irene Has Developed Good Anticyclonic Outflow And Is Now In A Light

Vertical Shear Environment. Thus...it Should Strengthen And Become

A Hurricane In 24-48 Hr. Mid/upper Level Dry Air Could Still Be A

Problem For Development...as Could Be An Eddy Of Cooler Sea Surface

Temperatures Along The Forecast Track. The Intensity Forecast

Calls For Irene To Reach 75 Kt In 48 Hr...then Level Off In

Intensity As It Passes Over The Eddy. Irene Should Moved Over

Warmer Ssts Again After 72 Hr...but How Much Vertical Shear May Be

Present At That Time Is Uncertain. Thus...the Intensity Forecast

Calls For No Change In Strength After That Time.

 

Five-day Tropical Cyclone Forecasts Have Considerable Uncertainty In

Both Location And Intensity...so It Is Still Too Early To Talk

About Specific Threats To The East Coast Of The United States...

Especially Given The Changes In The Forecast Track.

 

Forecaster Beven

[vicocala]

also there is a tropical wave, way out in the Atlantic that may become a tropical system within the next 24-48 hours, so stay tuned!

 

TROPICAL STORM IRENE DISCUSSION NUMBER 33

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

5 PM EDT FRI AUG 12 2005

 

AN AIR FORCE PLANE INVESTIGATING IRENE CONFIRMED EARLIER SATELLITE

INTENSITY ESTIMATES AT 1800 UTC. THE RECON MEASURED 64 KNOTS AT

FLIGHT LEVEL AND A MINIMUM PRESSURE OF 997 MB. IT ALSO REPORTED A

WELL-DEFINED CIRCULATION WITH GOOD RADAR PRESENTATION. BOTH SHEAR

AND SST ARE FAVORABLE FOR STRENGTHENING BUT SINCE NO GUIDANCE

BRINGS IRENE ABOVE A CATEGORY ONE HURRICANE...ONLY SLIGHT

INTENSIFICATION IS INDICATED.

 

IRENE HAS DECREASED ITS FORWARD SPEED AND IS MOVING TOWARD THE

NORTHWEST OR 310 DEGREES AT 9 KNOTS. THE CYCLONE HAS BEEN STEERED

BY THE FLOW AROUND A STRONG MID-LEVEL SUBTROPICAL RIDGE. AS THE

RIDGE MOVES EASTWARD...IRENE SHOULD TURN MORE TOWARD THE

NORTH-NORTHWEST AND NORTH AROUND THE RIDGE INTO AN AREA OF LIGHT

STEERING CURRENTS. THIS WOULD RESULT IN A SIGNIFICANT DECREASE IN

FORWARD SPEED DURING THE NEXT 2 TO 4 DAYS. IN FACT...IRENE COULD

BEGIN TO MEANDER FOR A WHILE. THEREAFTER...THE WESTERLIES ARE

EXPECTED TO BECOME ESTABLISHED AND THIS FLOW SHOULD TAKE IRENE

NORTHEASTWARD AWAY FROM THE U.S. COAST.

 

THE OFFICIAL TRACK FORECAST HAS BEEN GRADUALLY SHIFTING EASTWARD IN

AGREEMENT WITH GUIDANCE. THIS LESSENS THE POTENTIAL THREAT TO THE

UNITED STATES EAST COAST. A HIGH ALTITUDE NOAA JET IS CURRENTLY

SAMPLING THE ENVIRONMENT. THE DATA WILL GO INTO TONIGHT'S MODEL

RUNS.

 

NOTE: JUST AFTER THE COORDINATION CALL THE PLANE REPORTED A PEAK

WIND OF 75 KNOTS AT 850 MB. THE INITIAL INTENSITY HAS BEEN ADJUSTED

TO 60 KNOTS.

 

FORECASTER AVILA

[vicocala]

Tropical Storm Irene Discussion Number 34

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Fri Aug 12 2005

 

Since The Last Recon Report And 00z Satellite Intensity Estimates

...irene's Convective Pattern Has Degraded Somewhat. A 12/2245z Ssmi

Overpass Indicated A Sharp Dry Slot Had Pushed Into The Circulation

From The North...all The While Cloud Tops Have Warmed Near The

Center And A Cdo Feature Is No Longer Evident In Infrared Imagery.

Therefore...the Intensity Is Being Maintained At 60 Kt. However...

The Central Pressure Has Been Decreased To 991 Mb Based On A

12/2300z Pressure Of 995.9 Mb Reported By Buoy 41927 Located About

30 Nmi Northeast Of The Center...which Was Lower Than The Last

Recon Reported Central Pressure Of 997 Mb At 12/2023z.

 

The Best Motion Estimate Remains 310/09...which Is A Little To The

Right Of The Recon Fix Motion. A Noaa G-iv Jet Aircraft And An Air

Force Reserve Aircraft Have Been Conducting Synoptic Surveillance

Missions Around Irene This Evening. Dropsonde Data From Those

Aircraft Indicate A Slightly Stronger And More Westward Extension

Of The Mid-level Ridge Than Any Of The Models Were Indicating For

13/00z...with The Ukmet Having The Closest Verification. The Ridge

...albeit Somewhat Narrow...extends From Near Bermuda Westward To

North Carolina. A Shortwave Trough Has Moved Eastward Off The U.s.

East Coast And A Shortwave Ridge Over The Eastern Ohio Valley Is

Moving Eastward To Take The Place Of That Trough. In The Short Term

...this Should Build Or At Least Maintain The Existing Ridge To The

North Of Irene...which May Cause A Little More Westward Motion Than

Forecast For The Next 24 Hours Or So. After That...all The Models

Agree That Irene Will Erode The Ridge And Move Slowly Northward

Through The Ridge Between 70-72w Longitude...and Then Turn

East-northeastward By 72 Hours. However...given More Ridge Showing

Up In The Synoptic Dropsonde Data...there May Be A Westward Shift

In The 00z Model Guidance. For This Advisory...though...the

Official Track Will Remain Close To The Previous Forecast Track.

 

Brief Periods Of Intensification Will Probably Occur Through At

Least The Next 48 Hours Or So...despite Warm Ssts Of At Least 28c

And Favorable Upper-level Shear Conditions. This Is Mainly Due To

The Very Dry Air That Irene Will Be Moving Through And Constantly

Having To Mix Out. The Official Intensity Forecast Is Close To The

Previous Advisory And Remains A Little Stronger Than The Ships

Intensity Model...but Much Higher Than The Gfdl Model...which

Weakens Irene To Less Than 30 Kt In 48h.

 

Forecaster Stewart

[vicocala]

Tropical Storm Irene Discussion Number 35

Nws Tpc/national Hurricane Center Miami Fl

5 Am Edt Sat Aug 13 2005

 

A Deep Burst Of Convection Began At About 04z... And The Coldest

Convective Tops Remain Less Than -70 Degrees Celsius. An Air Force

Reconnaissance Aircraft Located The Circulation Center Just North

Of This Deep Convection... And Maximum 850 Mb Flight Level Winds Of

69 Kt Within It... Which Corresponds To Surface Winds Of 55 Kt.

The Aircraft Also Measured A Minimum Central Pressure A Bit Higher

Than Previously Thought... 997 Mb. Dvorak Data T Numbers Are

Unanimously 3.5/55 Kt. While There Are No Hard Numbers To Support

Maintaining The Intensity At 60 Kt... I Will Do So Based On The

Convective Organization Near The Circulation Center.

 

Aircraft Fixes During The Past Few Hours Indicate That Irene Is

Still Moving Northwestward... But A Little Farther East Than The

Previous Forecast Track... With Initial Motion Now Estimated At

320/9. Irene Is Being Steered Around A Nearby Deep Layer Ridge

Centered Over Bermuda. Data From Last Night's Synoptic

Surveillance Mission Does Not Seem To Have Led To Any Significant

Changes To Either The Initial Conditions Or The Forecasts From The

Various Dynamical Models. The Models Remain In General Agreement

That Irene Will Round The Ridge And Turn Toward The North During

The Next 36 Hours And Northeastward Beyond 72 Hours. None Of The

Models Indicate Landfall On The East Coast Of The United States.

Due To The Initial Motion Adjustment And To A Slight Eastward Trend

In The Model Tracks... The Official Forecast Is Adjusted To The

Right Or East Of The Previous Advisory During The First Three Days.

It Is Also Faster Since Irene Is Gaining Latitude More Quickly Now

And Will Become Embedded In The Westerlies To The North Of The

Ridge And Begin Accelerating On Day 4... As Shown By All Of The

Models Except The Left-outlying Gfdn.

 

Since Irene Is Still On The Cusp Of Becoming A Hurricane... It Could

Do So At Any Time. The Ships Peaks At 63 Kt In 72 Hours... While

The Gfdl Peaks Near 80 Kt Around That Same Time. The Official

Intensity Forecast Is Adjusted Only Slightly Downward Compared To

The Previous Advisory... To Come More In Line With Ships. Since

The New Official Forecast Is Faster... Irene Is Expected To Reach

Cooler Waters Sooner... So A Weakening Trend Is Introduced At The

End Of The Forecast... In Accordance With Both Gfdl And Ships.

 

Forecaster Knabb

[Sage]

Thanks Vicocala for the updates. From what it sounds like, if she behaves herself and makes the turn, it just may spare the US coast. Please let her be a lady.

[vicocala]

You are always welcome Sage tropical depression ten has formed I will start another thread on it. I am sailing in a couple of weeks. We don't need any more for a while, like until next year or the year after. LOL

 

TROPICAL STORM IRENE DISCUSSION NUMBER 37

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

5 PM EDT SAT AUG 13 2005

 

AS MENTIONED IN THE PREVIOUS DISCUSSION...IRENE HAS NOT BEEN ABLE TO

MAINTAIN A STEADY AND SYMMETRIC CLOUD PATTERN DURING ITS LIFETIME.

ONCE AGAIN THIS AFTERNOON THE CONVECTION HAS DECREASED AND THE

LOW-LEVEL CENTER IS BECOMING EXPOSED BUT REMAINS VERY VIGOROUS. IN

FACT...THE RECONNAISSANCE PLANE JUST MEASURED 70 KNOTS AT FLIGHT

LEVEL ON THE EAST SIDE OF THE CYCLONE. THE MINIMUM PRESSURE HAS

BEEN OSCILLATING BETWEEN 1000 AND 999 MB SINCE 1500 UTC. INITIAL

INTENSITY IS KEPT AT 60 KNOTS AND...ALTHOUGH THE WATER IS WARM AND

THE SHEAR IS LOW...THE LOW-LEVEL ENVIRONMENT REMAINS HOSTILE AS

SUGGESTED BY THE SHIPS MODEL. THEREFORE...ONLY A SMALL INCREASE IN

INTENSITY IS INDICATED.

 

BEST ESTIMATE OF THE INITIAL MOTION IS 320 DEGREES AT 9 KNOTS. THERE

HAS BEEN NO CHANGE IN THE FORECAST STEERING PATTERN SO IRENE SHOULD

GRADUALLY TURN TO THE NORTH AROUND THE SUBTROPICAL RIDGE. THE

CYCLONE WILL LIKELY BE EMBEDDED WITHIN THE SOUTHWESTERLY FLOW IN A

COUPLE OF DAYS AND SHOULD BEGIN TO MOVE TOWARD THE NORTHEAST WITH

AN INCREASE IN FORWARD SPEED. IRENE IS EXPECTED TO BE EXTRATROPICAL

BY 120 HOURS

[vicocala]

Tropical Storm Irene Discussion Number 38

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Sat Aug 13 2005

 

Irene Has Become A Little Better Organized During The Past 6 Hours

With A Strong Burst Of Deep Convection Having Developed Over And

South Of The Well-defined Low-level Center. A 13/2232z Ssmi

Overpass Depicted A Large But Closed Eye Feature In The Low-levels

...but The Mid- And Upper-level Circulations Were Still Open To The

North. The Last Recon Flight-level Wind Data Supported 55-60 Kt...

So With The Increase In Deep Convection Since That Time...an

Intensity Of At Least 60 Kt Seems... Although It Could Be Stronger.

If The Current Convective Trend Continues...then The Next Recon

Flight At 06z Should Find Irene As A Hurricane.

 

The Initial Motion Estimate Is 335/09. There Is No Significant

Change To The Previous Forecast Track Or Reasoning Through 96

Hours. Irene Appears To Be Moving Through A Weakness In The Bermuda

Ridge And It Should Gradually Turn Northward On Sunday And Then

Turn Northeastward And Accelerate By Monday As The Cyclone Gets

Caught Up In The Strong Mid-tropospheric Westerlies That Lie Across

The Northern U.s. And North Atlantic. By 96 Hours...a Deep-layer

Mid-latitude Low Pressure System Is Expected To Rapidly Accelerate

The Then Extratropical Irene Northeastward Into The Far North

Atlantic. The Official Track Is Similar To The Nhc Model Consensus

And Is Close To The Previous Forecast Through 96 Hours...and Then

Faster And To The Left After That.

 

Given The Impressive Low-level Eye Feature Noted In The Ssmi Imagery

And The Recent Increase In Deep Convection...irene Could Become A

Little Stronger Than What Is Indicated By The Official Forecast

Once The Cyclone Moves Onto And North Of The Bermuda Ridge Axis

Where The Steering Flows Should Become More Aligned And Reduce The

Shear. The Official Intensity Forecast Is Similar To The Previous

Package And Remains Above The Ships And Gfdl Intensity Models.

 

Forecaster Stewart

[vicocala]

Tropical Storm Irene Discussion Number 40

Nws Tpc/national Hurricane Center Miami Fl

11 Am Edt Sun Aug 14 2005

 

Irene Is Exhibiting A Fairly Impressive Cloud Pattern With

Well-defined Banding Features Over The Southern Semicircle.

Upper-level Outflow Appears Strong To The Southeast Through

Southwest. Measurement Of The Banding Using The Dvorak Technique

Easily Supports A Current Intensity Of 55 Kt. The Environment...in

Terms Of Vertical Shear And Sea Surface Temperatures...should Not

Inhibit Strengthening Within The Next 24 Hours. However Beyond

That Time Vertical Shear Is Forecast To Increase Rapidly As The

Storm Moves Into The Westerlies. Therefore Irene Has A Small

Window Of Opportunity For Strengthening. One More Aerial

Reconnaissance Mission Into Irene Is Scheduled For 18z Today To

Check The Position And Intensity.

 

Latest Center Fixes Indicate That The Heading Has Bent A Little To

The Right And Current Motion Estimate Is Now North-northeastward...

020/10. Irene Has Crossed The Axis Of The Subtropical Ridge And

Begun Recurvature Into The Westerlies. Track Guidance Is Generally

A Little Slower And Slightly Left Of That From The Previous

Advisory...but Only Small Adjustments Are Made To The Official

Forecast Track.

 

By 3 Days The Cyclone Is Likely To Be Losing Tropical

Characteristics...and By The End Of The Forecast Period The

Extratropical Version Of Irene Should Merge With A Larger

Baroclinic System.

 

Forecaster Pasch

[vicocala]

Tropical Storm Irene Discussion Number 41

Nws Tpc/national Hurricane Center Miami Fl

5 Pm Edt Sun Aug 14 2005

 

There Were 2 Air Force Hurricane Hunter Planes Investigating Irene

This Afternoon. They Found That The Central Pressure Had Dropped

To 992 Mb And The Highest 850 Mb Flight Level Wind Was 72 Knots.

These Data Indicate That Irene Is Just Below Hurricane Strength.

The Tropical Cyclone's Cloud Pattern Is The Best Organized It Has

Ever Been...with A Faint Eye Feature And Good Symmetry To The Cdo.

Upper-level Outflow Is Well-defined In All Quadrants Except The

Northeast. Since Irene Will Be Traversing The Warm Gulf Stream

Waters Over The Next 12-24 Hours...it May Very Well Become A

Hurricane Tonight Or Early Monday...before Vertical Shear Begins To

Increase Significantly.

 

No Change In The Estimated Motion...020/10. Irene Has Moved North

Of The Axis Of The Subtropical Ridge And Will Likely Turn Toward

The Northeast And East-northeast As It Interacts With The

Westerlies. Significant Acceleration Is Likely In About 72 Hours

As A 500 Mb Trough Approaches From Southeastern Canada. Some Of

The Models Have Not Initialized The Tropical Cyclone Very Well And

There Has Probably Caused Some Divergence In The Track Forecast

Guidance. The Official Forecast Is Based On A Compromise Of The

Track Models...and Continuity. Irene Is Likely To Become

Extratropical And Merge With A Larger Baroclinic Low Late In The

Forecast Period.

 

Forecaster Pasch

[vicocala]

Hurricane Irene Discussion Number 42

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Sun Aug 14 2005

 

An Air Force Reserve Unit Reconnaissance Aircraft On A Test Flight

Measured Strong Enough Winds At 850 Mb To Justify Upgrading Irene

To A Hurricane. Peak Flight Level Winds Were 88 Kt...which In Fact

Corresponds To About 70 Kt At The Surface...and That Is The

Assigned Advisory Intensity. Irene Has Good Outflow To The

Northeast...although The Westerlies Are Beginning To Impinge On The

Northwest Quadrant. Irene Will Be Over Warm Waters For Another 24

Hours Or So...and So Some Additional Strengthening Is Possible.

Global Models Suggest That The Shear Should Increase Sharply After

That Time As Well. Irene Is Likely To Become Extratropical And

Merge With A Larger Baroclinic Low Late In The Forecast Period.

 

The Initial Motion Is 025/10. Irene Has Rounded The Subtropical

Ridge And Will Soon Be Deflected To The Right By The Mid-latitude

Westerlies. The Flow Is Fairly Zonal However...and If Irene Turns

Sharply To The Right It May Take A Little While For Any Rapid

Acceleration To Occur. The Official Forecast Shows Only A Modest

Acceleration Until A Significant Mid-latitude Trough Approaches In

About 72 Hours. There Is Considerable Variation In The Speed Of

The Guidance Models...with The Gfs Being The Fastest. The Official

Forecast Is Not Nearly That Fast...but Is Fairly Close To The

Previous Advisory And Is Near The Fsu Superensemble.

 

Irene Becomes The Season's Third Hurricane. The Normal Number Of

Hurricanes Formed By This Date Is One. Only One Year...1966...

Had More Hurricanes Formed By This Point In The Season.

 

Forecaster Franklin

[vicocala]

Hurricane Irene Advisory Number 45

Nws Tpc/national Hurricane Center Miami Fl

5 Pm Ast Mon Aug 15 2005

 

...irene Moving East-northeastward Over Open Waters...

 

At 5 Pm Ast...2100z...the Center Of Hurricane Irene Was Located Near

Latitude 36.7 North... Longitude 66.0 West Or About 560 Miles...

900 Km... South-southwest Of Halifax Nova Scotia.

 

Irene Is Moving Toward The East-northeast Near 12 Mph

...19 Km/hr...and This Motion Is Expected To Continue For The Next

24 Hours.

 

Satellite Images Indicate That The Maximum Sustained Winds Are Near

90 Mph...150 Km/hr...with Higher Gusts. No Significant Change In

Strength Is Expected Overnight...but A Weakening Trend Is Likely To

Begin On Tuesday.

 

Hurricane Force Winds Extend Outward Up To 30 Miles... 45 Km...

From The Center...and Tropical Storm Force Winds Extend Outward Up

To 115 Miles...185 Km.

 

Estimated Minimum Central Pressure Is 980 Mb...28.94 Inches.

 

Repeating The 5 Pm Ast Position...36.7 N... 66.0 W. Movement

Toward...east-northeast Near 12 Mph. Maximum Sustained

Winds... 90 Mph. Minimum Central Pressure... 980 Mb.

 

The Next Advisory Will Be Issued By The National Hurricane Center At

11 Pm Ast.

 

Forecaster Pasch

[vicocala]

Hurricane Irene Discussion Number 46

Nws Tpc/national Hurricane Center Miami Fl

11 Pm Edt Mon Aug 15 2005

 

The Center Has Been Mostly Indistinct On Satellite Imagery This

Evening...and An Ssmi Overpass At 23z Showed The Eyewall Has Eroded

Slightly Compared To This Morning. However...dvorak Intensity

Estimates Are Unchanged And I Will Leave The Advisory Intensity At

80 Kt. There Is Currently No Outflow In The Northwest Quadrant As

Irene Is Beginning To Be Affected By The Upper-level Westerlies.

 

Based Largely On That Ssmi Overpass...the Initial Motion Is

Estimated To Be 085/12...faster Than Before...and Faster Than

Predicted By The 18z Guidance Models. In Addition...much Of The

Current Guidance Is Significantly Slower Than The Previous Official

Forecast. Given The Current Acceleration Trend...i Will Only Slow

The Previous Forecast A Little Bit And The New Forecast Is Fairly

Close To The Fsu Superensemble. Should Irene Take A Path Farther

South Than Expected...it Could Move Quite A Bit Slower Than

Forecast.

 

Irene Still Has About 36 Hours Over Warm Water...but The Shear Is

Expected To Increase Before Then. This Shear Should Induce A

Weakening Trend...and Indeed The Microwave Data Suggest This Trend

Has Already Begun. Weakening Would Likely Be Slower Than Forecast

Should Irene Take A More Southerly Track. Cooler Waters And An

Approaching Mid-latitude Trough Are Expected To Result In An

Extratropical Transition Within About 48 Hours.

 

Forecaster Franklin

[vicocala]

Hurricane Irene Discussion Number 47

Nws Tpc/national Hurricane Center Miami Fl

5 Am Edt Tue Aug 16 2005

 

While The Overall Convective Cloud Appearance Has Changed Little

During The Past 6 Hours In Infrared Satellite Imagery...several

Sssmi...amsu...and Trmm Microwave Overpasses Have Shown A Gradual

Degradation In The Inner Core Convective Features And Eye

Structure. A Distinct Eastward Tilt Of The Eye Was Noted In 0447z

And 0625z Trmm Overpasses...although The Latter Image Suggested

That Less Tilting Of The Eye Was Occurring As Compared To Earlier

Passes. Satellite Intensity Estimates Are T4.5/77kt From Both Tafb

And Sab. Given The Ragged Eye Appearance Noted In The Microwave

Data...the Initial Intensity Has Been Decreased To 75 Kt.

 

The Initial Motion Estimate Is 090/08 Based On The Last 6 Hours Of

Microwave Satellite Positions. The Eastward Motion Is Likely Due To

A Shortwave Caught Up In The Faster Westerlies Well To The North Of

Irene That Is Bypassing The Cyclone. This Has Resulted In Weaker

Westerly Steering Flow On The South Side Of An East-west Oriented

Jetstream. However...a Much Stronger And Higher Amplitude Shortwave

Trough Over The Eastern Great Lakes And Ohio Valley Region Is

Expected To Move Quickly Eastward And Gradually Lift Out Irene To

The Northeast By 36 Hours...and Then Rapidly Accelerate The Cyclone

By 48 Hours. Between 36-48 Hours...irene Will Be Moving Over

Sub-24c Ssts...so Transition To A Powerful Extratropical Low

Pressure System Is Expected. Due To The More Eastward Initial

Position...the Official Forecast Track Is A Little To The Right Of

The Previous Forecast...and Is Close To The Nhc Model Consensus.

 

The Initial Eastward Motion Will Keep Irene Over Warmer Water A

Little Longer Than Previously Expected...but A Gradual Increase In

The Westerly Vertical Shear Will Likely Overcome Any Positive

Contribution From The 28c Ssts. Once Irene Hits The Icy Waters Of

The North Atlantic In About 48 Hours...any Remaining Tropical

Characteristics Should Quickly Disappear. However...with Such A

Strong Shortwave Trough And Jetstream Approaching...the Increasing

Baroclinic Energy Should Keep Irene A Rather Potent Extratropical

Low Pressure System Over The Far North Atlantic.