EPAC: IRWIN - Post - Tropical

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Kingarabian
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#41 Postby Kingarabian » Sun Oct 09, 2011 4:53 am

Appears to be that convection is starting to increase once more.
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Re: EPAC: IRWIN - Tropical Storm

#42 Postby cycloneye » Sun Oct 09, 2011 9:45 am

TROPICAL STORM IRWIN DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 AM PDT SUN OCT 09 2011

IRWIN COULD BE MAKING A COMEBACK. DEEP CONVECTION HAS CONTINUED TO
REDEVELOP IN A CURVED BAND IN THE SOUTHERN SEMICIRCLE DURING THE
LAST SEVERAL HOURS. HOWEVER...THE OVERALL STRUCTURE OF THE CYCLONE
HAS NOT CHANGED MUCH. GIVEN THAT DVORAK T-NUMBERS ARE ABOUT THE
SAME AS SIX HOURS AGO...THE INITIAL INTENSITY IS HELD AT 40 KT.

THE SCATTER OF THE LATEST FIXES MAKES ESTIMATING THE CENTER LOCATION
DIFFICULT...BUT THE INITIAL MOTION APPEARS TO BE THE SAME AS
BEFORE...055/04. IRWIN IS EXPECTED TO BE STEERED GENERALLY EASTWARD
DURING THE NEXT DAY OR TWO BY LOW- TO MID-LEVEL WESTERLY FLOW. FROM
48-96 HOURS...THE GFS AND ECMWF MODELS CONTINUE TO SHOW A BINARY
INTERACTION BETWEEN IRWIN AND A PIECE OF SHORTWAVE ENERGY CUTTING
OFF SOUTHWEST OF BAJA CALIFORNIA...WHICH COULD IMPART A TEMPORARY
SOUTH-OF-EAST MOTION AND THEN A TURN TOWARD THE NORTHEAST. BY 120
HOURS...THE STEERING FLOW AROUND IRWIN BEGINS TO CHANGE...WITH THE
GFS SHOWING THE CYCLONE COMING TO A HALT AND THE OTHER GUIDANCE
FAVORING A BEND TOWARD THE EAST OR EAST-SOUTHEAST. THE OFFICIAL
TRACK FORECAST IS A HAIR TO THE RIGHT OF THE PREVIOUS ONE...IN
FAVOR OF THE MORE RELIABLE GFS/ECMWF SOLUTIONS AND FOLLOWING THE
MULTI-MODEL CONSENSUS. THERE CONTINUES TO BE A LARGE AMOUNT OF
SPREAD IN THE MODEL SOLUTIONS...PRIMARILY LATE IN THE FORECAST
PERIOD...WHICH MAKES THE FORECAST CONFIDENCE LOW AT THAT TIME.

ALTHOUGH THE RETURN OF DEEP CONVECTION COULD SIGNAL SOME RE-
INTENSIFICATION...THE EFFECTS OF EASTERLY SHEAR...THE INGESTION OF
A MORE STABLE AIR MASS TO ITS NORTH...AND THE CURRENT LARGE RMW
COULD BE LIMITING FACTORS DURING THE NEXT DAY OR TWO. A PERSISTENCE
OF THE EASTERLY SHEAR AND THE POTENTIAL ADVERSE EFFECTS OF THE SST
WAKE ASSOCIATED WITH JOVA COULD BE CONSIDERATIONS BEYOND 72 HOURS.
ALTHOUGH THE GFDL AND HWRF FORECASTS ARE AGAIN MORE AGGRESSIVE...
THE LGEM/SHIPS GUIDANCE CONTINUE TO SHOW A GRADUAL DECAY. THE
OFFICIAL INTENSITY FORECAST ASSUMES THAT IRWIN WILL HOLD ITS OWN IN
THE SHORT TERM AND...SIMILAR TO THE PREVIOUS ADVISORY...CALLS FOR
SOME POSSIBILITY OF RE-INTENSIFICATION LATER ON.


FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 15.2N 119.8W 40 KT 45 MPH
12H 10/0000Z 15.5N 118.9W 40 KT 45 MPH
24H 10/1200Z 15.8N 117.6W 40 KT 45 MPH
36H 11/0000Z 15.8N 116.2W 40 KT 45 MPH
48H 11/1200Z 15.5N 114.8W 40 KT 45 MPH
72H 12/1200Z 15.8N 111.3W 40 KT 45 MPH
96H 13/1200Z 17.6N 107.8W 45 KT 50 MPH
120H 14/1200Z 19.0N 106.5W 50 KT 60 MPH

$$
FORECASTER KIMBERLAIN
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Re: EPAC: IRWIN - Tropical Storm

#43 Postby cycloneye » Sun Oct 09, 2011 2:07 pm

EP, 11, 2011100918, , BEST, 0, 152N, 1196W, 40, 1000, TS
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Re: EPAC: IRWIN - Tropical Storm

#44 Postby cycloneye » Sun Oct 09, 2011 3:35 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 15
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
200 PM PDT SUN OCT 09 2011

IRWIN APPEARS TO BE SLIGHTLY BETTER ORGANIZED. THE CYCLONE HAS BEEN
MAINTAINING DEEP CONVECTION IN A BAND WRAPPING AROUND THE SOUTHERN
SEMICIRCLE FOR ALMOST 12 HOURS IN AN EASTERLY SHEAR ENVIRONMENT.
DVORAK T-NUMBERS HAVE INCREASED SOME...AND THE INITIAL INTENSITY IS
RAISED TO 45 KT IN ACCORDANCE WITH THE DVORAK ESTIMATE FROM TAFB.

SHROUDED BY ITS CONVECTIVE CLOUD CANOPY...THE CENTER OF IRWIN
CONTINUES TO BE DIFFICULT TO LOCATE IN CONVENTIONAL SATELLITE
IMAGERY. MICROWAVE FIXES SUGGEST THAT IRWIN IS MOVING 060/04...A
TAD TO THE RIGHT OF THE PREVIOUS ESTIMATE. EMBEDDED IN LOW- TO
MID-LEVEL WESTERLY FLOW...IRWIN IS EXPECTED TO MOVE GENERALLY
EAST-NORTHEASTWARD FOR THE NEXT DAY OR SO. THE INTERACTION OF IRWIN
WITH A MID-TROPOSPHERIC SHORTWAVE TROUGH CUTTING OFF INTO A LOW
SOUTHWEST OF BAJA CALIFORNIA SHOULD CAUSE THE TRACK TO BEND
EAST-SOUTHEAST AND THEN NORTHEAST AROUND THE LOW IN 36-72 HOURS.
THE NORTHWARD MIGRATION OF THE PACIFIC ITCZ ALONG WITH A CONTINUED
WESTERLY MID-LEVEL STEERING SHOULD GUIDE IRWIN ON AN EASTWARD OR
EVEN EAST-SOUTHEASTWARD COURSE LATER ON. THE TRACK GUIDANCE HAS
COME INTO MUCH BETTER AGREEMENT ON THIS SCENARIO THIS CYCLE. THE
OVERALL EASTWARD SHIFT IN THE GUIDANCE REQUIRES A SIZABLE
ADJUSTMENT TO THE PREVIOUS OFFICIAL FORECAST AT DAYS 4-5 BUT IS
STILL TO THE LEFT OF THE MULTI-MODEL CONSENSUS.

INTENSITY-WISE...IRWIN MAY HAVE SOME STRUGGLES AHEAD. THE STORM
COULD BE TAPPING A MORE STABLE AIR MASS TO ITS NORTHWEST WHICH...IN
COMBINATION WITH PERSISTENT EASTERLY SHEAR...MAY DIMINISH ITS
CHANCE FOR INTENSIFICATION IN THE SHORT TERM. A PERSISTENCE OF
EASTERLY SHEAR AND THE POTENTIAL ADVERSE EFFECTS OF THE SST WAKE
ASSOCIATED WITH JOVA COULD BE NEGATIVE FACTORS FOR INTENSIFICATION
LATER IN THE FORECAST PERIOD. THE STATISTICAL-DYNAMICAL GUIDANCE IS
BETTER AGREEMENT THAN BEFORE...BOTH SUGGESTING LITTLE CHANGE IN
INTENSITY FOLLOWED BY A SLOW DECAY. THE OFFICIAL FORECAST IS
SIMILAR TO THE PREVIOUS ONE AS IN GENERAL AGREEMENT WITH THE
INTENSITY CONSENSUS AIDS...ALBEIT SLIGHTLY LOWER AT DAYS 4-5.

FORECAST POSITIONS AND MAX WINDS

INIT 09/2100Z 15.2N 119.3W 45 KT 50 MPH
12H 10/0600Z 15.7N 118.4W 45 KT 50 MPH
24H 10/1800Z 15.8N 117.0W 40 KT 45 MPH
36H 11/0600Z 15.6N 115.5W 40 KT 45 MPH
48H 11/1800Z 15.4N 113.8W 40 KT 45 MPH
72H 12/1800Z 16.0N 110.0W 40 KT 45 MPH
96H 13/1800Z 17.5N 106.5W 40 KT 45 MPH
120H 14/1800Z 18.0N 105.0W 45 KT 50 MPH

$$
FORECASTER KIMBERLAIN
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Re: EPAC: IRWIN - Tropical Storm

#45 Postby cycloneye » Sun Oct 09, 2011 9:46 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 PM PDT SUN OCT 09 2011

DEEP CONVECTION ASSOCIATED WITH IRWIN HAS BEEN GRADUALLY DECREASING
THIS EVENING...MUCH LIKE WHAT OCCURRED YESTERDAY AT THIS TIME.
ASIDE FROM THE WEAKENING CONVECTION...MICROWAVE DATA INDICATE THAT
THE OVERALL STRUCTURE HAS CHANGED LITTLE DURING THE LAST SEVERAL
HOURS WITH THE LOW-LEVEL CENTER LOCATED TO THE NORTH OF A CURVED
BAND. THE INITIAL WIND SPEED IS HELD AT 45 KT...BUT THIS COULD BE
A LITTLE GENEROUS.

THE TROPICAL STORM HAS NOW TURNED TO THE EAST AND IS MOVING A LITTLE
FASTER...AND THE LATEST INITIAL MOTION ESTIMATE IS 085/5. AN
EASTWARD OR PERHAPS EAST-SOUTHEASTWARD MOTION IS FORECAST DURING
THE NEXT COUPLE OF DAYS AS THE CYCLONE MOVES IN THE FLOW TO THE
EAST OF A SHARPENING TROUGH OR CUTOFF LOW TO THE SOUTHWEST OF THE
BAJA PENINSULA. IRWIN IS THEN FORECAST TO TRACK JUST NORTH OF DUE
EAST...BRINGING IT NEAR THE COAST OF SOUTHWESTERN MEXICO BY THE END
OF THE FORECAST PERIOD. A SLOW DOWN IS FORECAST BY DAY 5...AS MANY
OF THE GLOBAL MODELS SHOW A RIDGE BUILDING TO THE NORTH OF THE
STORM BY THAT TIME. THE OFFICIAL TRACK FORECAST HAS BEEN ADJUSTED
SOUTHWARD...ESPECIALLY AT DAYS FOUR AND FIVE...TO COME INTO BETTER
AGREEMENT WITH THE LATEST GUIDANCE.

IRWIN IS CURRENTLY IN A RELATIVELY LOW WIND SHEAR ENVIRONMENT AND
OVER ABOUT 28C WATERS. HOWEVER...THE STORM STILL LIES NEAR STABLE
AIR AND THAT COULD BE A REASON WHY IT HAS BEEN STRUGGLING TO
STRENGTHEN RECENTLY. ALTHOUGH THE CYCLONE WILL BE MOVING INTO A
MORE MOIST ENVIRONMENT LATER THIS WEEK...THE SHIPS MODEL SHOWS
EASTERLY SHEAR INCREASING OVER IRWIN. MEANWHILE...THE FORECAST
TRACK TAKES IRWIN OVER THE COOL WATER WAKE CREATED BY HURRICANE
JOVA. THE INTENSITY MODELS ARE QUITE DIVERGENT WITH THE SHIPS/LGEM
SHOWING A GRADUAL WEAKENING...AND THE GFDL/HWRF BRINGING IRWIN TO
HURRICANE STRENGTH. GIVEN THE MIXED SIGNALS IN BOTH THE
ENVIRONMENTAL FACTORS AND THE MODELS...THE OFFICIAL FORECAST SHOWS
IRWIN REMAINING STEADY STATE THROUGHOUT THE PERIOD.

FORECAST POSITIONS AND MAX WINDS

INIT 10/0300Z 15.2N 118.7W 45 KT 50 MPH
12H 10/1200Z 15.4N 117.6W 45 KT 50 MPH
24H 11/0000Z 15.4N 116.1W 45 KT 50 MPH
36H 11/1200Z 15.2N 114.5W 45 KT 50 MPH
48H 12/0000Z 15.1N 112.8W 45 KT 50 MPH
72H 13/0000Z 16.2N 108.5W 45 KT 50 MPH
96H 14/0000Z 17.0N 105.0W 45 KT 50 MPH
120H 15/0000Z 17.0N 103.5W 45 KT 50 MPH

$$
FORECASTER CANGIALOSI
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Re: EPAC: IRWIN - Tropical Storm

#46 Postby cycloneye » Mon Oct 10, 2011 9:56 am

Irwin weakens a little bit more.


TROPICAL STORM IRWIN DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 AM PDT MON OCT 10 2011

SIMILAR TO WHAT OCCURRED YESTERDAY...IRWIN HAS LOST MOST OF ITS DEEP
CONVECTION. ALL THAT REMAINS IS A PATCH OF MEAGER CONVECTION THAT
HAS RECENTLY FORMED SOUTH OF THE CIRCULATION CENTER. DVORAK
T-NUMBERS HAVE DECREASED ACCORDINGLY...AND A BLEND OF THE LATEST T-
AND CI-NUMBERS ARE USED TO SET THE INITIAL INTENSITY ESTIMATE AT 35
KT. IRWIN APPEARS TO BE PULLING IN RELATIVELY COOLER AND MORE
STABLE AIR FROM THE WEST...AS EVIDENCED BY THE SOUTHWARD
DISPLACEMENT OF THE NEARBY STRATOCUMULUS FIELD. THIS COULD
TEMPORARILY BE LIMITING ANY RE-DEVELOPMENT OF SIGNIFICANT DEEP
CONVECTION AND HENCE INTENSIFICATION. EASTERLY SHEAR IS ANOTHER
LIMITING FACTOR AND IS FORECAST BY THE DYNAMICAL MODELS TO PERSIST
AT ROUGHLY THE SAME MAGNITUDE FOR THE NEXT 3-4 DAYS AND POSSIBLY
EVEN INCREASE AT THE END OF THE FORECAST PERIOD. WHILE THE
DYNAMICAL GUIDANCE SHOWS SOME STRENGTHENING...THE OBJECTIVE
STATISTICAL OUTPUT CONTINUES TO SHOW A SLOW DECAY. THE OFFICIAL
INTENSITY FORECAST IS REDUCED A BIT FROM THE PREVIOUS ONE TO
ACCOUNT FOR THE RECENT WEAKENING. IT ALSO LEANS TOWARD A BLEND OF
SHIPS/LGEM AND THE INTENSITY CONSENSUS AIDS...GIVEN HOW MUCH THE
SYSTEM IS CURRENTLY STRUGGLING.

RECENT CENTER FIXES REMAIN UNCERTAIN...AND THE INITIAL MOTION
ESTIMATE APPEARS TO BE 085/06. IRWIN IS EXPECTED TO BE CARRIED ON
AN ATYPICAL EASTWARD AND THE NORTHEASTWARD TRACK FOR THE NEXT
SEVERAL DAYS AS IT BENDS CYCLONICALLY AROUND A CUT-OFF LOW
DEVELOPING SOUTHWEST OF BAJA CALIFORNIA. BY ABOUT 96 HOURS...
IRWIN...PERHAPS AS A SHALLOW CYCLONE...IS LIKELY TO BE PULLED BACK
TOWARD THE EAST AND EVEN SOUTHEAST INTO A BROAD LOW- TO MID-LEVEL
CYCLONIC GYRE OVER MEXICO. THE MODEL GUIDANCE IS IN GOOD AGREEMENT
ON THIS SCENARIO...AND THE CURRENT FORECAST IS ESSENTIALLY AN
UPDATE OF THE PREVIOUS ONE.

FORECAST POSITIONS AND MAX WINDS

INIT 10/1500Z 15.0N 117.7W 35 KT 40 MPH
12H 11/0000Z 15.1N 116.4W 35 KT 40 MPH
24H 11/1200Z 15.0N 114.8W 40 KT 45 MPH
36H 12/0000Z 15.1N 112.9W 40 KT 45 MPH
48H 12/1200Z 15.6N 110.9W 40 KT 45 MPH
72H 13/1200Z 16.9N 107.4W 40 KT 45 MPH
96H 14/1200Z 17.1N 105.1W 40 KT 45 MPH
120H 15/1200Z 16.4N 103.9W 35 KT 40 MPH

$$
FORECASTER KIMBERLAIN
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Re: EPAC: IRWIN - Tropical Storm

#47 Postby cycloneye » Mon Oct 10, 2011 3:36 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
200 PM PDT MON OCT 10 2011

CONVECTION ASSOCIATED WITH IRWIN REMAINS LIMITED AND DISORGANIZED.
THERE IS A RAGGED PATCH REMOVED FROM THE CENTER ON THE SOUTH SIDE
OF THE CIRCULATION...WITH SPOTTY AND SOMEWHAT SHALLOW CONVECTION IN
A NORTHERN BAND. DVORAK T-NUMBERS ARE UNCHANGED FROM 1200 UTC...SO
THE INITIAL INTENSITY IS HELD AT 35 KT. AN EASTERLY SHEAR
ENVIRONMENT CONTINUES TO PREVAIL OVER THE TROPICAL CYCLONE...WITH A
MORE STABLE AIR MASS CONTINUING TO WRAP AROUND THE WEST SIDE OF THE
CIRCULATION. WHILE THE EFFECT OF THE NEARBY STRATOCUMULUS FIELD
MAY LESSEN AS IRWIN MOVES FARTHER AWAY FROM IT IN THE NEXT DAY OR
TWO...THE SHIPS MODEL OUTPUT INDICATES NO RELENTING OF THE SHEAR.
IN FACT...SOME INCREASE IN SHEAR IS SEEN TOWARD THE END OF THE
FORECAST PERIOD...AND THERE IS SOME CHANCE THAT IRWIN COULD
DEGENERATE INTO A SHALLOW CYCLONE BY THAT TIME. THE NHC INTENSITY
FORECAST HAS BEEN LOWERED FROM THE PREVIOUS ONE AND CONTINUES TO
SIDE WITH THE STATISTICAL-DYNAMICAL GUIDANCE.

AS IS THE CASE WITH WEAK SYSTEMS...THE CENTER HAS BEEN DIFFICULT TO
LOCATE. VISIBLE SATELLITE IMAGES SHED SOME LIGHT ON THE CENTER
LOCATION AND SUGGEST THAT IRWIN IS MOVING 085/06. THE CYCLONE
SHOULD BE CARRIED EASTWARD AND THEN NORTHEASTWARD WITH SOME
INCREASE IN FORWARD SPEED DURING THE NEXT 2-3 DAYS AS IT BENDS
CYCLONICALLY AROUND A MID-TROPOSPHERIC LOW CUTTING OFF SOUTHWEST OF
BAJA CALIFORNIA. AFTER ABOUT 4 DAYS...IRWIN IS EXPECTED TO TURN
EASTWARD AND EAST-SOUTHEASTWARD AS IT BECOMES EMBEDDED IN THE
STRENGTHENING LOW-LEVEL WESTERLY FLOW ASSOCIATED WITH A NORTHWARD
SHIFT OF THE PACIFIC ITCZ OVER MEXICO. ALTHOUGH GLOBAL MODELS SHOW
SOME MID-LEVEL RIDGING BUILDING NORTH OF IRWIN BY THAT TIME...THE
SHALLOW CYCLONE WILL PROBABLY NOT BE ABLE TO ESCAPE FROM THE
LOW-LEVEL WESTERLIES. SOME LARGE DIFFERENCES ARE SEEN IN THE TRACK
GUIDANCE AT DAYS 4-5...LIKELY DUE TO MODEL DIFFERENCES IN THE
VORTEX DEPTH. THE NEW OFFICIAL TRACK FORECAST HAS BEEN LARGELY
UNCHANGED FROM THE PREVIOUS ONE...AND IS BETWEEN THE MULTI-MODEL
CONSENSUS AND THE SHALLOW BAM TRACK.

FORECAST POSITIONS AND MAX WINDS

INIT 10/2100Z 14.9N 116.9W 35 KT 40 MPH
12H 11/0600Z 14.9N 115.7W 30 KT 35 MPH
24H 11/1800Z 14.9N 114.1W 30 KT 35 MPH
36H 12/0600Z 15.3N 111.9W 30 KT 35 MPH
48H 12/1800Z 16.1N 109.7W 30 KT 35 MPH
72H 13/1800Z 17.3N 106.2W 30 KT 35 MPH
96H 14/1800Z 17.0N 104.0W 30 KT 35 MPH
120H 15/1800Z 16.5N 103.0W 30 KT 35 MPH

$$
FORECASTER KIMBERLAIN
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#48 Postby brunota2003 » Mon Oct 10, 2011 6:46 pm

Watch the visible loop on the NHC site...you can see the clouds dissipating off to the west of Irwin.
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Re: EPAC: IRWIN - Tropical Depression

#49 Postby cycloneye » Mon Oct 10, 2011 9:39 pm

TROPICAL DEPRESSION IRWIN DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 PM PDT MON OCT 10 2011

IRWIN CONTINUES TO WEAKEN. ONLY A COUPLE OF PATCHES OF DEEP
CONVECTION REMAIN AND THESE ARE CONFINED TO LOOSELY ORGANIZED
CURVED BANDS. IN ADDITION...THE LATEST MICROWAVE DATA INDICATE THAT
THE LOW-LEVEL CENTER OF IRWIN HAS BECOME ELONGATED DURING THE PAST
FEW HOURS. DVORAK CLASSIFICATIONS AT 0000 UTC WERE 30 AND 35 KT
FROM TAFB AND SAB...RESPECTIVELY. GIVEN THE DECREASE IN THE
CONVECTIVE ORGANIZATION SINCE THAT TIME AND THE DEGRADED APPEARANCE
IN MICROWAVE IMAGES...THE INITIAL WIND SPEED IS SET AT THE LOWER
ESTIMATE...MAKING IRWIN A TROPICAL DEPRESSION.

THE DEPRESSION CONTINUES TO MOVE EASTWARD AT ABOUT 6 KT. THE GLOBAL
MODELS SHOW A MID-LEVEL CUTOFF LOW DEVELOPING TO THE WEST OF THE
TROPICAL CYCLONE IN ABOUT 24 HOURS. ALTHOUGH THE MODELS ARE IN
AGREEMENT IN THE EVOLUTION OF THE SYNOPTIC PATTERN...THEY DIFFER ON
HOW MUCH IRWIN INTERACTS WITH THE MID-LEVEL LOW. THE GFS MODEL
SHOWS LESS INTERACTION...AND THEREFORE KEEPS IRWIN ON A GENERAL
EASTWARD TRACK FOR THE NEXT FEW DAYS. CONVERSELY...THE ECMWF MODEL
SHOWS IRWIN MOVING CYCLONICALLY AROUND THE EAST SIDE OF THE
MID-LEVEL LOW...RESULTING IN A TRACK CONSIDERABLY NORTH OF THE GFS.
REGARDLESS...BY THE END OF THE FORECAST PERIOD ALL OF THE MODELS
SHOW A SLOW DOWN AND TURN TO THE SOUTHEAST AS IRWIN IS EXPECTED TO
BECOME EMBEDDED IN LOW TO MID-LEVEL NORTHWESTERLY FLOW BY THAT
TIME. THE OFFICIAL FORECAST LIES BETWEEN THE GFS AND ECMWF MODELS
AND IS NEAR THE HFIP MODEL CONSENSUS.

ALTHOUGH IRWIN IS EXPECTED TO BE MOVING INTO A MORE MOIST
ENVIRONMENT DURING THE NEXT FEW DAYS...AN INCREASE IN SOUTHWESTERLY
MID-LEVEL FLOW IS EXPECTED AS THE AFOREMENTIONED LOW DEVELOPS.
THEREFORE...THE OFFICIAL FORECAST SHOWS NO CHANGE IN STRENGTH
THROUGHOUT THE PERIOD. HOWEVER...IT IS POSSIBLE THAT IRWIN COULD
DEGENERATE INTO A REMNANT LOW AT SOME POINT DURING THE NEXT FEW
DAYS.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 15.0N 116.3W 30 KT 35 MPH
12H 11/1200Z 15.0N 115.2W 30 KT 35 MPH
24H 12/0000Z 15.1N 113.4W 30 KT 35 MPH
36H 12/1200Z 15.7N 111.1W 30 KT 35 MPH
48H 13/0000Z 16.5N 108.9W 30 KT 35 MPH
72H 14/0000Z 17.4N 105.3W 30 KT 35 MPH
96H 15/0000Z 16.5N 103.5W 30 KT 35 MPH
120H 16/0000Z 16.0N 103.0W 30 KT 35 MPH

$$
FORECASTER CANGIALOSI
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#50 Postby Kingarabian » Mon Oct 10, 2011 11:35 pm

A very weird storm in Irwin....
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#51 Postby Chacor » Tue Oct 11, 2011 9:43 am

Back to TS.
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Re: EPAC: IRWIN - Tropical Storm

#52 Postby cycloneye » Tue Oct 11, 2011 9:44 am

BULLETIN
TROPICAL STORM IRWIN ADVISORY NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 AM PDT TUE OCT 11 2011

...IRWIN MAKES A COMEBACK...


SUMMARY OF 800 AM PDT...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...15.3N 115.0W
ABOUT 620 MI...1000 KM SSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...E OR 80 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 AM PDT...1500 UTC...THE CENTER OF TROPICAL STORM IRWIN WAS
LOCATED NEAR LATITUDE 15.3 NORTH...LONGITUDE 115.0 WEST. IRWIN IS
MOVING TOWARD THE EAST NEAR 8 MPH...13 KM/H. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE FOR TODAY...WITH A TURN TOWARD THE
EAST-NORTHEAST FORECAST BY EARLY WEDNESDAY.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 40 MPH...65 KM/H...
WITH HIGHER GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING
THE NEXT 48 HOURS.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 60 MILES...95 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB...29.62 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...200 PM PDT.

$$
FORECASTER KIMBERLAIN


TROPICAL STORM IRWIN DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 AM PDT TUE OCT 11 2011

SATELLITE IMAGERY INDICATES THAT IRWIN IS MAKING A COMEBACK...AGAIN.
A CLUSTER OF DEEP CONVECTION HAS RECENTLY FORMED AND INCREASED IN
COVERAGE OVER THE EASTERN SEMICIRCLE...WITH CLOUD TOP TEMPERATURES
LOWER THAN -80C. SATELLITE INTENSITY ESTIMATES HAVE INCREASED DUE
TO THE CONVECTIVE REFORMATION...SO THE INITIAL INTENSITY IS RAISED
TO 35 KT.

THE FUTURE FOR IRWIN DOES NOT LOOK BRIGHT. DEEP CONVECTION
ASSOCIATED WITH IRWIN HAS GENERALLY BEEN SUFFERING AS THE CYCLONE
APPARENTLY TAPS RELATIVELY STABLE AIR ASSOCIATED WITH A NEARBY
STRATOCUMULUS FIELD. AS IRWIN PULLS AWAY FROM THIS AREA...IT IS
ASSUMED THAT THE EASTERLY SHEAR WILL BE STRONG ENOUGH TO PREVENT
ANY SIGNIFICANT RE-INTENSIFICATION. AFTER ABOUT 36 HOURS...A FURTHER
INCREASE IN EASTERLY SHEAR IS EXPECTED AS IRWIN ENTERS AN
ENVIRONMENT OF STRENGTHENING LOW-LEVEL WESTERLY FLOW AND EASTERLIES
ALOFT. WEAKENING SHOULD RESULT...AND IRWIN IS SHOWN AS A SHALLOW
REMNANT LOW BY DAY 5...THOUGH IT WOULD NOT BE SURPRISING IF THIS
DEGENERATION OCCURRED SOONER. THE NEW NHC INTENSITY FORECAST IS A
BIT HIGHER THAN THE PREVIOUS FORECAST IN THE SHORT TERM BASED ON
CURRENT TRENDS...AND IT IS SIMILAR TO THE PREVIOUS ONE AT
LATER TIMES. OVERALL...IT IS IN BEST AGREEMENT WITH THE STATISTICAL-
DYNAMICAL AIDS.

THE CENTER CONTINUES TO BE HARD TO PIN DOWN...EVEN WITH MICROWAVE
IMAGERY. USING SATELLITE DATA AND SOME EXTRAPOLATION...IT
APPEARS THAT IRWIN IS MOVING 080/06. MODEL GUIDANCE...EXCEPT FOR
THE GFS...SHOWS IRWIN HEADING NORTHEASTWARD DURING THE NEXT 12-60
HOURS AS IT SWINGS AROUND A MID-TROPOSPHERIC LOW CUTTING OFF
SOUTHWEST OF BAJA CALIFORNIA. AFTER THAT...GLOBAL MODELS DEPICT
IRWIN...LIKELY AS A SHALLOW CYCLONE...BEING DRAWN INTO A BROAD
CYCLONIC FLOW NEAR MEXICO AND TURNING GENERALLY SOUTHEASTWARD
AND SLOWING DOWN. THE NEW NHC TRACK FORECAST IS SIMILAR TO BUT NORTH
OF THE PREVIOUS ONE AND ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE.


FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 15.3N 115.0W 35 KT 40 MPH
12H 12/0000Z 15.5N 113.7W 35 KT 40 MPH
24H 12/1200Z 16.1N 111.7W 35 KT 40 MPH
36H 13/0000Z 17.0N 109.4W 30 KT 35 MPH
48H 13/1200Z 17.5N 107.7W 30 KT 35 MPH
72H 14/1200Z 17.6N 105.1W 30 KT 35 MPH
96H 15/1200Z 16.5N 104.3W 25 KT 30 MPH
120H 16/1200Z 16.0N 104.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER KIMBERLAIN
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Re: EPAC: IRWIN - Tropical Storm

#53 Postby cycloneye » Tue Oct 11, 2011 3:39 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 23
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
200 PM PDT TUE OCT 11 2011

A BALL OF COLD-TOPPED CONVECTION HAS PERSISTED NEAR THE ESTIMATED
CENTER OF IRWIN FOR A WHILE NOW...WITH VISIBLE SATELLITE
IMAGERY INDICATING SOME INCREASE IN THE ORGANIZATION OF BANDING
FEATURES IN THE LAST FEW HOURS. DVORAK INTENSITY ESTIMATES HAVE
INCREASED TO 35 KT AND 45 KT FROM SAB AND TAFB...RESPECTIVELY.
GIVEN THAT A 1650 UTC ASCAT OVERPASS SHOWED A FEW 35 KT WIND
VECTORS...THE INITIAL INTENSITY IS RAISED TO 40 KT.

EVEN THOUGH IRWIN HAS MADE A COMEBACK...ITS LONGER-TERM FUTURE IS
NOT AS PROMISING. THE REJUVENATED APPEARANCE OF IRWIN COINCIDES
WITH ITS DEPARTURE FROM A NEARBY STRATOCUMULUS FIELD AND ASSOCIATED
STABLE AIR MASS. WITH ONLY MODERATE SHEAR FORECAST DURING THE NEXT
DAY OR SO...THERE IS SOME LIKELIHOOD OF SHORT-TERM INTENSIFICATION
AND THE INTENSITY GUIDANCE REFLECTS THIS. THE CYCLONE IS THEN
EXPECTED TO ENTER A HIGH SHEAR ENVIRONMENT DUE TO STRONG LOW-LEVEL
WESTERLY FLOW AND EASTERLIES ALOFT IN 2 TO 5 DAYS. THIS PROLONGED
EXPOSURE TO SHEAR WILL PROBABLY CAUSE IRWIN TO WEAKEN AND THE
CYCLONE IS EXPECTED TO DEGENERATE TO A REMNANT LOW BY AROUND DAY 4.
THE OFFICIAL INTENSITY FORECAST IS BASICALLY IN LINE WITH THE
STATISTICAL AND INTENSITY CONSENSUS AIDS AND HIGHER THAN THE
PREVIOUS ONE THROUGH 48 HOURS TO ACCOUNT FOR CURRENT TRENDS.
BEYOND THAT TIME...IT IS ESSENTIALLY THE SAME.

THE CENTER APPEARS TO BE FARTHER SOUTH RELATIVE TO THE PREVIOUS
ESTIMATE...AND IT IS UNKNOWN WHETHER THIS REPRESENTS A REFORMATION
OF THE CENTER OR AN ACTUAL MOVEMENT. THE LATEST FIXES YIELD A
LONGER-TERM MOTION OF 095/05. THE INTERACTION OF IRWIN AND A
MID-TROPOSPHERIC LOW SOUTHWEST OF BAJA CALIFORNIA SHOULD RESULT IN
A BRIEF TURN TOWARD THE EAST-NORTHEAST OR NORTHEAST WITH AN
INCREASE IN FORWARD SPEED DURING THE NEXT DAY OR TWO. THE GUIDANCE
THEN DEPICTS IRWIN BEING PULLED EASTWARD AND THEN SOUTHEASTWARD
INTO A BROAD MONSOON-TYPE FLOW TO THE SOUTH OF MEXICO. AFTER
BECOMING A REMNANT LOW...MOST OF THE GLOBAL MODELS TURN THE SYSTEM
BACK TO THE WEST AS A LOW-LEVEL RIDGE BUILDS TO THE NORTH. THE
OFFICIAL FORECAST HAS BEEN MODIFIED TO INDICATE THIS SCENARIO AND
IS NEAR BUT GENERALLY A LITTLE FASTER THAN THE PREVIOUS ONE BETWEEN
24-72 HOURS...TO THE RIGHT OF THE MULTI-MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 11/2100Z 14.9N 114.2W 40 KT 45 MPH
12H 12/0600Z 15.2N 113.1W 45 KT 50 MPH
24H 12/1800Z 16.1N 110.9W 50 KT 60 MPH
36H 13/0600Z 17.1N 108.9W 40 KT 45 MPH
48H 13/1800Z 17.3N 107.0W 35 KT 40 MPH
72H 14/1800Z 16.7N 104.5W 30 KT 35 MPH
96H 15/1800Z 16.0N 105.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 16/1800Z 15.5N 106.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER KIMBERLAIN
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Re: EPAC: IRWIN - Tropical Storm

#54 Postby cycloneye » Tue Oct 11, 2011 9:34 pm

TCDEP1

TROPICAL STORM IRWIN DISCUSSION NUMBER 24
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 PM PDT TUE OCT 11 2011

THE CONVECTIVE PATTERN OF IRWIN HAS CHANGED CONSIDERABLY DURING THE
LAST SEVERAL HOURS. AROUND 1800 UTC...A FAIRLY CIRCULAR AREA OF
CONVECTION EXISTED NEAR THE ESTIMATED LOW-LEVEL CENTER. SINCE THAT
TIME...THE CONVECTION HAS BECOME MUCH MORE SPREAD OUT WITH THE MAIN
AREA IN A RAGGED-LOOKING CLUSTER TO THE NORTH OF THE CENTER. THE
INITIAL WIND SPEED IS HELD AT 40 KT...WHICH IS IN AGREEMENT WITH
THE DVORAK CI NUMBERS FROM TAFB AND SAB...AND ADT ESTIMATES FROM
UW-CIMSS.

IRWIN CONTINUES TO MOVE JUST SOUTH OF DUE EAST...AND THE INITIAL
MOTION ESTIMATE IS ABOUT THE SAME AS BEFORE...095/8. WATER VAPOR
IMAGERY INDICATES THAT THE ADVERTISED MID-LEVEL LOW IS BEGINNING TO
DEVELOP A FEW HUNDRED MILES TO THE SOUTHWEST OF THE BAJA PENINSULA.
THIS FEATURE IS EXPECTED TO CAUSE IRWIN TO TURN EAST-NORTHEASTWARD
WITH SOME INCREASE IN FORWARD SPEED DURING THE NEXT 36 TO 48 HOURS.
BEYOND THAT TIME...IRWIN IS FORECAST TO SLOW DOWN AND MAKE A
CLOCKWISE LOOP AS A LOW- TO MID-LEVEL RIDGE BUILDS TO THE NORTH OF
THE CYCLONE. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE
AND LIES NEAR THE MULTI-MODEL CONSENSUS.

THE ENVIRONMENT AHEAD OF IRWIN IS NOT FAVORABLE FOR STRENGTHENING.
THE INTERACTION WITH THE AFOREMENTIONED MID-LEVEL LOW AND THE
EXPECTED SIGNIFICANT INCREASE IN EASTERLY SHEAR BY THE END OF THE
FORECAST PERIOD SHOULD LIMIT THE STORM FROM INTENSIFYING MUCH...IF
AT ALL. THEREFORE...THE OFFICIAL FORECAST GENERALLY SHOWS LITTLE
CHANGE IN STRENGTH FOR THE NEXT 36 HOURS...FOLLOWED BY GRADUAL
WEAKENING. THIS FORECAST IS A LITTLE LOWER THAN THE PREVIOUS ONE
AND IS IN BEST AGREEMENT WITH THE LGEM GUIDANCE.

FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 14.8N 113.3W 40 KT 45 MPH
12H 12/1200Z 15.5N 111.8W 40 KT 45 MPH
24H 13/0000Z 16.5N 109.8W 45 KT 50 MPH
36H 13/1200Z 17.1N 107.9W 40 KT 45 MPH
48H 14/0000Z 17.1N 106.2W 35 KT 40 MPH
72H 15/0000Z 16.2N 104.2W 30 KT 35 MPH
96H 16/0000Z 15.5N 105.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 17/0000Z 15.5N 107.0W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER CANGIALOSI
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Re: EPAC: IRWIN - Tropical Storm

#55 Postby cycloneye » Wed Oct 12, 2011 3:50 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 27
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
200 PM PDT WED OCT 12 2011

CONVECTION ASSOCIATED WITH IRWIN HAS DECREASED THIS AFTERNOON...WITH
THE LOW-LEVEL CENTER EXPOSED TO THE EAST OF A SMALL AREA OF SHOWERS
OR THUNDERSTORMS. AN ASCAT OVERPASS AT 1630 UTC SHOWED SEVERAL
35 KT WIND BARBS SOUTH OF THE CENTER...AND BASED ON THIS IRWIN
REMAINS A TROPICAL STORM FOR THIS ADVISORY. THE SCATTEROMETER DATA
WAS ALSO USED TO REVISE THE INITIAL AND FORECAST WIND RADII.

THE INITIAL MOTION IS NOW 060/15. WATER VAPOR IMAGERY INDICATES AN
UPPER-LEVEL LOW NEAR 19N117W...WHICH IS LIKELY HELPING TO STEER THE
CYCLONE EAST-NORTHEASTWARD. AFTER 12-24 HOURS...THE DYNAMICAL
MODELS FORECAST A MID/UPPER-LEVEL RIDGE TO BUILD NORTH OF THE
TROPICAL CYCLONE. AT THE SAME TIME...IRWIN IS FORECAST TO
ENCOUNTER LOW-LEVEL WESTERLY FLOW ASSOCIATED WITH A MONSOON-TYPE
CIRCULATION DEVELOPING TO THE EAST. THESE FACTORS SHOULD CAUSE
IRWIN TO TURN EASTWARD AND THEN SOUTHEASTWARD FROM 24-48 HOURS WITH
A DECREASE IN FORWARD SPEED. AFTER THAT...THE RIDGE TO THE NORTH IS
FORECAST TO BECOME THE DOMINANT STEERING INFLUENCE...CAUSING IRWIN
TO TURN WESTWARD TO COMPLETE A LOOP OR HAIRPIN TURN. THE NEW
FORECAST TRACK IS FASTER THAN AND NORTH OF THE PREVIOUS TRACK DURING
THE FIRST 48 HOURS BASED MAINLY ON THE INITIAL POSITION AND MOTION.
AFTER 48 HOURS IT LIES JUST NORTH OF THE PREVIOUS FORECAST. THE
NEW TRACK IS NEAR THE CENTER OF THE TRACK GUIDANCE ENVELOPE.

EASTERLY SHEAR IS LIKELY TO CONTINUE THROUGH THE FORECAST PERIOD DUE
TO THE UPPER-LEVEL ANTICYCLONE ASSOCIATED WITH JOVA...TROPICAL
DEPRESSION TWELVE-E...AND THE DEVELOPING MONSOON CIRCULATION. THE
INTENSITY GUIDANCE SHOWS IRWIN SLOWLY WEAKENING THROUGH 48 HOURS...
AND SO DOES THE INTENSITY FORECAST. THE INTENSITY FORECAST IS
PROBLEMATIC AFTER 48 HOURS DUE TO UNCERTAINTIES IN THE FORECAST
UPPER-LEVEL WINDS. DUE TO THE THIS...OFFICIAL FORECAST MAINTAINS
THE PREVIOUS SCENARIO OF HAVING IRWIN DEGENERATE TO A REMNANT LOW
BY 96 HOURS. HOWEVER... SEVERAL OF THE INTENSITY GUIDANCE MODELS
SHOW IRWIN RE-INTENSIFYING AS IT MOVES WESTWARD...AND LATER
FORECASTS MAY HAVE TO BE NUDGED IN THAT DIRECTION IF THE MODEL
TRENDS CONTINUE.

FORECAST POSITIONS AND MAX WINDS

INIT 12/2100Z 16.9N 109.4W 35 KT 40 MPH
12H 13/0600Z 17.7N 107.7W 35 KT 40 MPH
24H 13/1800Z 18.0N 105.6W 30 KT 35 MPH
36H 14/0600Z 17.8N 104.5W 30 KT 35 MPH
48H 14/1800Z 17.0N 103.8W 30 KT 35 MPH
72H 15/1800Z 16.0N 104.5W 30 KT 35 MPH
96H 16/1800Z 16.0N 106.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 17/1800Z 16.0N 109.5W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
FORECASTER BEVEN
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Re: EPAC: IRWIN - Tropical Depression

#56 Postby cycloneye » Wed Oct 12, 2011 9:40 pm

TROPICAL DEPRESSION IRWIN DISCUSSION NUMBER 28
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 PM PDT WED OCT 12 2011

SATELLITE IMAGES INDICATE THAT IRWIN HAS WEAKENED...AND THE CYCLONE
IS NOW NEARLY DEVOID OF DEEP CONVECTION. DVORAK CLASSIFICATIONS
SUPPORT LOWERING THE INITIAL WIND SPEED TO 30 KT...AND THIS MAKES
IRWIN A TROPICAL DEPRESSION ONCE AGAIN. GIVEN THE RECENT DECLINE IN
THUNDERSTORM ACTIVITY AND BECAUSE THE SHEAR IS NOT EXPECTED TO
LESSEN MUCH ON THURSDAY...IRWIN IS NOW FORECAST TO BECOME A REMNANT
LOW BY 36 HOURS...BUT THIS COULD OCCUR EVEN SOONER. SOME OF THE
MODELS SHOW IRWIN RESTRENGTHENING BY THE END OF THE FORECAST
PERIOD. THE OFFICIAL FORECAST...HOWEVER...KEEPS IRWIN AS A REMNANT
LOW BEYOND 36 HOURS DUE TO THE HIGH UNCERTAINTY AT THE LONGER TIME
RANGE.

IRWIN IS MOVING TO THE NORTHEAST AT ABOUT 13 KT ON THE EAST SIDE OF
A CUTOFF LOW. THE DEPRESSION IS EXPECTED TO TURN TO THE EAST AND
SLOW DOWN DURING THE NEXT 12 TO 24 HOURS STEERED BY THE LOW-LEVEL
WESTERLY FLOW. BEYOND THAT TIME...IRWIN...OR ITS REMNANT LOW...IS
EXPECTED TO MAKE A CLOCKWISE LOOP AS A LOW- TO MID-LEVEL RIDGE
BUILDS TO ITS NORTH. THE OFFICIAL FORECAST IS SIMILAR TO THE
PREVIOUS ONE AND IS CLOSEST TO THE ECMWF MODEL AND THE HFIP MODEL
CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 13/0300Z 17.8N 108.6W 30 KT 35 MPH
12H 13/1200Z 18.2N 107.0W 30 KT 35 MPH
24H 14/0000Z 18.1N 105.3W 30 KT 35 MPH
36H 14/1200Z 17.4N 104.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 15/0000Z 16.7N 104.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 16/0000Z 16.0N 105.6W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 17/0000Z 16.0N 108.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 18/0000Z 16.0N 111.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
FORECASTER CANGIALOSI
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#57 Postby Chacor » Thu Oct 13, 2011 5:57 am

We'll find out if Irwin regenerates after becoming post-tropical. If it does, it would have one of the most interesting EPac tracks in history imo.
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Re: EPAC: IRWIN - Tropical Storm

#58 Postby cycloneye » Thu Oct 13, 2011 9:41 am

The back and forth continues with Irwin,now once again back to Tropical Storm.

BULLETIN
TROPICAL STORM IRWIN ADVISORY NUMBER 30
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 AM PDT THU OCT 13 2011

...IRWIN INTENSIFIES TO A TROPICAL STORM AGAIN...


SUMMARY OF 800 AM PDT...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...18.7N 107.2W
ABOUT 190 MI...305 KM W OF MANZANILLO MEXICO
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...ENE OR 60 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 AM PDT...1500 UTC...THE CENTER OF TROPICAL STORM IRWIN WAS
LOCATED NEAR LATITUDE 18.7 NORTH...LONGITUDE 107.2 WEST. IRWIN IS
MOVING TOWARD THE EAST-NORTHEAST NEAR 9 MPH...15 KM/H. A TURN TOWARD
THE EAST AND A DECREASE IN FORWARD SPEED ARE EXPECTED LATER TODAY...
FOLLOWED BY A TURN TOWARD THE SOUTH BY EARLY FRIDAY.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 40 MPH...65 KM/H...
WITH HIGHER GUSTS. LITTLE CHANGE IN STRENGTH IS EXPECTED DURING
THE NEXT 48 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 35 MILES...55 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB...29.62 INCHES.


HAZARDS AFFECTING LAND
----------------------
NONE


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...200 PM PDT.

$$
FORECASTER BRENNAN


TROPICAL STORM IRWIN DISCUSSION NUMBER 30
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 AM PDT THU OCT 13 2011

DEEP CONVECTION HAS MADE A COMEBACK NEAR THE CENTER OF IRWIN OVER
THE PAST FEW HOURS...WITH A CONVECTIVE BAND ALSO FORMING NORTHWEST
OF THE CENTER. BASED ON THE 1200 UTC TAFB DVORAK ESTIMATE...THE
SYSTEM IS UPGRADED TO A TROPICAL STORM WITH AN INTENSITY OF 35 KT.
THE SHIPS MODEL ANALYSES SHOW THAT THE VERTICAL SHEAR HAS GRADUALLY
DECREASED OVER IRWIN IN THE LAST 12 HOURS...WHICH MAY HAVE ALLOWED
THE RECENT INCREASE IN CONVECTION. THE INTENSITY GUIDANCE SHOWS
LITTLE CHANGE IN THE FIRST 36 HOURS AS THE CYCLONE MOVES OVER WARM
WATERS BUT REMAINS IN A RELATIVELY DRY MID-LEVEL ENVIRONMENT...AND
THE NHC FORECAST FOLLOWS THAT THINKING. THE GFDL...LGEM...AND SHIPS
MODELS THEN SHOW IRWIN STRENGTHENING TO STRONG TROPICAL STORM
STATUS AS IT REMAINS OVER WARM WATERS IN LIGHT TO MODERATE EASTERLY
TO SOUTHEASTERLY SHEAR. HOWEVER...MANY OF THE GLOBAL MODELS SHOW
THE CIRCULATION WEAKENING OR DISSIPATING BY THE END OF THE PERIOD.
GIVEN THIS UNCERTAINTY...THE NHC FORECAST SHOWS ONLY A SMALL
INCREASE IN INTENSITY AT 48 HOURS...WITH NO CHANGE AFTER THAT TIME.

IRWIN HAS SLOWED AND TURNED A LITTLE TO THE RIGHT...WITH AN
ESTIMATED INITIAL MOTION OF 060/8. ALL OF THE GUIDANCE SHOWS IRWIN
MAKING AN ABRUPT ANTICYCLONIC LOOP IN THE NEXT 72 HOURS...AS A
MID-LEVEL RIDGE BUILDS NORTH OF THE CYCLONE. THE GUIDANCE SUITE HAS
TRENDED TOWARD A SHARPER LOOP DURING THE FIRST 72 HOURS...AND
TOWARD A MORE SOUTHERLY TRACK AT DAYS 4 AND 5. THE OFFICIAL
FORECAST HAS BEEN ADJUSTED TOWARD THE NEW MULTI-MODEL CONSENSUS...
AND LIES TO THE RIGHT OF THE PREVIOUS PACKAGE THROUGH 48 HOURS AND
TO THE LEFT OF IT AT DAYS 4 AND 5.

GIVEN THE SMALL AREA OF TROPICAL STORM FORCE WINDS AND THE EXPECTED
SHARP TURN TOWARD THE SOUTH OVER THE NEXT COUPLE OF DAYS...TROPICAL
STORM WATCHES OR WARNINGS ARE NOT REQUIRED FOR THE COAST OF MEXICO
AT THIS TIME.


FORECAST POSITIONS AND MAX WINDS

INIT 13/1500Z 18.7N 107.2W 35 KT 40 MPH
12H 14/0000Z 18.7N 106.3W 35 KT 40 MPH
24H 14/1200Z 18.2N 105.7W 35 KT 40 MPH
36H 15/0000Z 17.2N 105.3W 35 KT 40 MPH
48H 15/1200Z 16.2N 105.6W 40 KT 45 MPH
72H 16/1200Z 15.0N 107.0W 40 KT 45 MPH
96H 17/1200Z 14.5N 108.5W 40 KT 45 MPH
120H 18/1200Z 15.0N 110.0W 40 KT 45 MPH

$$
FORECASTER BRENNAN
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Re: EPAC: IRWIN - Tropical Storm

#59 Postby cycloneye » Thu Oct 13, 2011 3:37 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 31
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
200 PM PDT THU OCT 13 2011

DEEP CONVECTION HAS WANED NEAR THE CENTER OF IRWIN DURING THE PAST
FEW HOURS...HOWEVER 1800 UTC DVORAK ESTIMATES FROM TAFB AND SAB
SUPPORT HOLDING THE INITIAL INTENSITY AT 35 KT FOR THIS ADVISORY.
THE OVERALL INTENSITY FORECAST REASONING REMAINS UNCHANGED...WITH
LITTLE CHANGE EXPECTED FOR THE NEXT DAY OR SO AS IRWIN CONTINUES
MOVING THROUGH A RELATIVELY DRY MID-LEVEL ENVIRONMENT DESPITE BEING
SITUATED OVER VERY WARM SSTS. WHILE MOST OF THE GUIDANCE CONTINUES
TO SHOW STRENGTHENING AT 48 HOURS AND BEYOND...THE OFFICIAL
FORECAST WILL SHOW ONLY A SMALL INCREASE IN INTENSITY AT 2 OR 3
DAYS. A LITTLE WEAKENING IS FORECAST LATE IN THE PERIOD AS THE
VERTICAL SHEAR IS EXPECTED TO INCREASE. THE NHC FORECAST IS BELOW
THE INTENSITY CONSENSUS THROUGH THE PERIOD AND IS CLOSE TO THE HWRF
MODEL.

IRWIN HAS SLOWED AND TURNED TOWARD THE EAST OVER THE PAST FEW
HOURS...AND THE INITIAL MOTION ESTIMATE IS 090/05. A MID-LEVEL RIDGE
CURRENTLY CENTERED NEAR 30N 120W WILL BUILD SOUTHEASTWARD OVER THE
NEXT COUPLE OF DAYS...WHICH SHOULD FORCE A IRWIN TO TURN SHARPLY
TOWARD THE SOUTH AND THEN TOWARD THE SOUTH-SOUTHWEST IN THE NEXT 48
HOURS. FOR THIS CYCLE THE GUIDANCE HAS TRENDED AGAIN TOWARD A SHAPER
SOUTHWARD TURN IN THE SHORT TERM WITH A SLIGHTLY FASTER FORWARD
MOTION...AND SO HAS THE NHC FORECAST. BY 72 HOURS THE RIDGE BEGINS
TO SHIFT NORTHWARD AND LEAVES IRWIN IN A REGION OF WEAK STEERING
CURRENTS. NOT SURPRISINGLY THE SPREAD IN THE TRACK GUIDANCE
INCREASES MARKEDLY AT DAYS 4 AND 5...WITH THE GFS AND UKMET SHOWING
A TURN BACK TOWARD THE EAST WHILE THE ECMWF SHOWS A MUCH WEAKER
IRWIN MOVING MORE QUICKLY WESTWARD. THE NHC FORECAST SHOWS A SLOW
WESTWARD MOTION AT THE END OF THE PERIOD DUE TO THE LARGE
UNCERTAINTY...AND HAS BEEN ADJUSTED A LITTLE TO THE SOUTH TOWARD
THE NEW MULTI-MODEL CONSENSUS.

GIVEN THE SMALL AREA OF TROPICAL STORM FORCE WINDS AND THE EXPECTED
SHARP TURN TOWARD THE SOUTH OVER THE NEXT COUPLE OF DAYS...TROPICAL
STORM WATCHES OR WARNINGS ARE NOT REQUIRED FOR THE COAST OF MEXICO
AT THIS TIME.


FORECAST POSITIONS AND MAX WINDS

INIT 13/2100Z 18.6N 106.5W 35 KT 40 MPH
12H 14/0600Z 18.4N 106.1W 35 KT 40 MPH
24H 14/1800Z 17.5N 105.7W 35 KT 40 MPH
36H 15/0600Z 16.5N 105.7W 35 KT 40 MPH
48H 15/1800Z 15.5N 106.1W 40 KT 45 MPH
72H 16/1800Z 14.5N 107.5W 40 KT 45 MPH
96H 17/1800Z 14.5N 108.5W 35 KT 40 MPH
120H 18/1800Z 14.5N 109.5W 35 KT 40 MPH

$$
FORECASTER BRENNAN
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Re: EPAC: IRWIN - Tropical Storm

#60 Postby cycloneye » Thu Oct 13, 2011 9:37 pm

TROPICAL STORM IRWIN DISCUSSION NUMBER 32
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011
800 PM PDT THU OCT 13 2011

TONIGHT WE HAVE RECEIVED UNCOMMON BUT WELCOME DATA. THERE ARE 3
DIFFERENT SHIPS LOCATED NEAR AND TO THE EAST OF IRWIN THAT REPORTED
AT THE SAME TIME...AND THEY ALL MEASURED WINDS OF TROPICAL STORM
FORCE. ALTHOUGH THE CLOUD PATTERN HAS NOT BECOME ANY BETTER
ORGANIZED AND THE DVORAK T-NUMBERS REMAIN UNCHANGED...THE INITIAL
INTENSITY HAS BEEN INCREASED TO 40 KNOTS BASED ON THESE SHIP
OBSERVATIONS. SOME MODELS SUGGEST THAT IRWIN SHOULD BEGIN TO
STRENGTHEN SLIGHTLY...BUT THERE IS AN UNFAVORABLE MID-LEVEL DRY
ENVIRONMENT SURROUNDING THE CYCLONE. THE LOW SHEAR AND THE WARM
OCEAN COULD COMPENSATE FOR THE DRY AIR...SO IRWIN IS KEPT AS A 35-
TO 40-KT TROPICAL STORM THROUGH 5 DAYS IN THIS ADVISORY.

THE CENTER HAS BEEN MEANDERING DURING THE PAST SEVERAL HOURS...AND
LITTLE MOTION IS ANTICIPATED DURING THE NEXT 12 TO 24 HOURS.
THEREAFTER...LIGHT MID-LEVEL NORTHERLY AND NORTHEASTERLY FLOW
SHOULD DEVELOP NEAR THE CYCLONE AS SUGGESTED BY GLOBAL MODELS...AND
THIS PATTERN SHOULD FORCE IRWIN ON A VERY SLOW SOUTHWARD AND
SOUTHWESTWARD TRACK THROUGH 5 DAYS. MOST OF GUIDANCE UNANIMOUSLY
FAVOR SUCH MOTION.

GIVEN THE SMALL AREA OF TROPICAL STORM FORCE WINDS...THE FACT THAT
IRWIN IS BASICALLY STATIONARY...AND THAT IT IS FORECAST TO MOVE
AWAY FROM MEXICO OVER THE NEXT COUPLE OF DAYS...TROPICAL STORM
WATCHES OR WARNINGS ARE NOT REQUIRED FOR THE COAST OF MEXICO AT
THIS TIME. HOWEVER...DATA FROM THESE SHIPS INDICATE THAT THE
TROPICAL STORM FORCE WINDS ARE NOT TOO FAR FROM THE MEXICAN COAST.



FORECAST POSITIONS AND MAX WINDS

INIT 14/0300Z 19.2N 106.6W 40 KT 45 MPH
12H 14/1200Z 19.0N 106.5W 35 KT 40 MPH
24H 15/0000Z 18.0N 106.2W 35 KT 40 MPH
36H 15/1200Z 16.8N 106.2W 35 KT 40 MPH
48H 16/0000Z 15.8N 107.0W 40 KT 45 MPH
72H 17/0000Z 15.0N 108.0W 40 KT 45 MPH
96H 18/0000Z 15.0N 109.0W 40 KT 45 MPH
120H 19/0000Z 15.0N 109.5W 40 KT 45 MPH

$$
FORECASTER AVILA
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