EPAC: IGNACIO - Post-Tropical

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Kingarabian
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#321 Postby Kingarabian » Sun Aug 30, 2015 5:48 am

000
WTPA43 PHFO 300905
TCDCP3

HURRICANE IGNACIO DISCUSSION NUMBER 22
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 PM HST SAT AUG 29 2015

IGNACIO PRESENTS A WELL-DEFINED 20 NM WIDE EYE WITH A DEEP
CONVECTIVE CANOPY WHICH HAS BEEN STEADILY SHRINKING SINCE 0600 UTC.
ALL THREE SATELLITE CENTERS DERIVED SUBJECTIVE DVORAK SATELLITE
INTENSITY ESTIMATES OF 6.0...115 KT...AT 0600 UTC. UW-CIMSS ADT WAS
HIGHER AT 6.3 OR 122 KT. HOWEVER...WEATHER RECONNAISSANCE AIRCRAFT
SFMR FOUND 126 KT WITHIN THE NORTHEAST EYEWALL DURING THE SECOND OF
THREE...YES THREE...CENTER FLYTHROUGHS. SPLASH WIND CORRECTED
CENTRAL PRESSURE WAS FOUND TO BE 942 MB...LOWER THAN EXPECTED...ON
THE FIRST PASS BUT 945 MB ON THE THIRD PASS. BOTH PRESSURE ESTIMATES
WERE LOWER THAN IN THE PREVIOUS ADVISORY. IGNACIO LIKELY REACHED A
PEAK INTENSITY OF 125 KT AS THE AIRCRAFT WAS SAMPLING ITS
STRUCTURE...AND THIS WILL BE THE INITIAL INTENSITY FOR THIS
ADVISORY.

FORECAST PHILOSOPHY HAS CHANGED LITTLE SINCE THE LAST ADVISORY.
IGNACIO CONTINUES TO TRACK NORTHWEST...315 DEGREES AT 7 KT OVER THE
PAST 12 HOURS...THROUGH A WEAKNESS IN THE MID-LEVEL RIDGE EAST OF
HAWAII AND TOWARD A WEAK TROUGH LOCATED TO THE NORTH OF THE
NORTHWESTERN HAWAIIAN ISLANDS. THE ONLY CHALLENGE IS THAT...IN THE
SHORTER RANGE...THREE TO SIX HOURS...THERE ARE HINTS OF A MORE
NORTHERLY MOTION. LIKE THE LAST FEW RUNS...TRACK GUIDANCE THIS TIME
REMAINS TIGHTLY PACKED...TAKING THIS HURRICANE ALMOST IN A STRAIGHT
LINE NORTHWESTWARD THROUGH THE FIVE-DAY FORECAST PERIOD. HWRF AND
GFDL SHIFTED A BIT TO THE RIGHT...AS DID MOST CONSENSUS BLENDS.
HOWEVER...THE GFS SHIFTED SLIGHTLY LEFT. WE HAVE CONSISTENTLY KEPT
THE FORECAST TRACK ALONG THE LEFT EDGE OF THE GUIDANCE ENVELOPE AND
WE WILL DO SO THIS TIME AS WELL. THAT SAID...THE FORECAST TRACK WAS
SHIFTED SLIGHTLY TO THE RIGHT TO ACCOUNT FOR THE SHORT TERM MOTION
BEING A BIT MORE NORTHERLY THAN 12 HOUR MOTION. THIS CHANGE IS
ACTUALLY QUITE CONSERVATIVE...KEEPING THE TRACK LEFT OF CONSENSUS
AND CLOSELY ALIGNED WITH GFS. A 1 OR 2 KT DECREASE IN FORWARD MOTION
WAS ALSO INTRODUCED THROUGH 36 HOURS...NOT ENOUGH TO CHANGE THE
STATUS OF TROPICAL STORM WATCHES ACROSS THE HAWAIIAN ISLANDS.

SATELLITE LOOP SHOWS SHEAR IS BEGINNING TO TAKE ITS TOLL ON THIS
SYSTEM...IN SPITE OF THE INTENSITY MAX LIKELY REACHED A FEW HOURS
AGO. OUTFLOW APPEARS TO BE HINDERED TO THE NORTHWEST AND THE EROSION
ALONG THE WESTERN FLANK OF THE DEEP CONVECTIVE CANOPY SEEMS TO
CONFIRM THE PRESENCE OF INCREASING WESTERLY SHEAR. SHIPS INTENSITY
GUIDANCE DEPICTS STEADILY INCREASING SHEAR THROUGH 96 HOURS AND THE
FORECAST CALLS FOR IGNACIO TO FOLLOW A WEAKENING TREND SIMILAR TO
THAT OF THE LAST ADVISORY. WE KEEP THIS SYSTEM STRONGER THAN SHIPS
DEPICTS THROUGH DAY FIVE BUT WEAKER THAN DEPICTED IN DYNAMIC
MODELS.

IGNACIO WILL PASS CLOSE ENOUGH TO THE MAIN HAWAIIAN ISLANDS TO
JUSTIFY KEEPING A TROPICAL STORM WATCH IN EFFECT FOR THE BIG ISLAND
AND THE ISLANDS OF MAUI COUNTY.

FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 17.4N 147.9W 125 KT 145 MPH
12H 30/1800Z 18.2N 148.9W 115 KT 135 MPH
24H 31/0600Z 19.2N 150.2W 110 KT 125 MPH
36H 31/1800Z 20.3N 151.6W 95 KT 110 MPH
48H 01/0600Z 21.3N 152.9W 80 KT 90 MPH
72H 02/0600Z 23.4N 155.8W 75 KT 85 MPH
96H 03/0600Z 25.6N 159.2W 65 KT 75 MPH
120H 04/0600Z 27.8N 162.3W 60 KT 70 MPH

$$
FORECASTER POWELL
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#322 Postby CrazyC83 » Sun Aug 30, 2015 8:30 am

Based on the Recon data, I'm thinking Ignacio peaked at 130 kt just before the flight around 0300Z.
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#323 Postby cycloneye » Sun Aug 30, 2015 10:40 am

HURRICANE IGNACIO DISCUSSION NUMBER 23
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
500 AM HST SUN AUG 30 2015

THE SATELLITE PRESENTATION OF IGNACIO HAS DEFINITELY DEGRADED SINCE
THE LAST ADVISORY...WITH A RAGGED 20 NM WIDE EYE BECOMING
INTERMITTENTLY CLOUD-FILLED AND THE DEEP CONVECTIVE CANOPY BECOMING
NOTICEABLY SLIMMER ESPECIALLY ACROSS THE WEST AND SOUTHWEST
QUADRANTS. HOWEVER...SYSTEM SYMMETRY APPEARS TO HAVE RECOVERED A BIT
SINCE 1200 UTC. ALL THREE SATELLITE CENTERS DERIVED SUBJECTIVE
DVORAK SATELLITE INTENSITY ESTIMATES OF 6.0...115 KT...LIKE LAST
TIME. THE DIFFERENCE IS THAT ALL THESE ESTIMATES HAVE LOWER FINAL T
NUMBERS...DENOTING A WEAKENING TREND. UW-CIMSS ADT WAS 5.8 AT 1200
UTC...110 KT. IGNACIO INTENSITY LIKELY PEAKED 6 TO 10 HOURS AGO AND
EVERYTHING SHOWS A WEAKENING SYSTEM NOW. HOWEVER...SINCE WEATHER
RECONNAISSANCE AIRCRAFT SFMR SHOWED INTENSITY OF ABOUT 125 KT LAST
EVENING...WE WILL ASSIGN AN INITIAL INTENSITY OF 120 KT FOR THIS
ADVISORY...LOWER THAN LAST TIME BUT CONTINUED HIGHER THAN SATELLITE
ESTIMATES ALONE. WEATHER RECONNAISSANCE AIRCRAFT WILL FLY ONCE AGAIN
IN TIME FOR THE 1800 UTC ANALYSIS CYCLE.

THE SUSPECTED MORE NORTHERLY SHORT-TERM MOTION NOTED LAST TIME HAS
PERSISTED LONG ENOUGH TO BECOME OFFICIAL 12 HOUR MOTION...WHICH IS
NOW 330 DEGREES AT 8 KT. THE STEERING MECHANISM IS THE SAME...WITH A
WEAKNESS IN THE MID-LEVEL RIDGE EAST OF HAWAII ALLOWING IGNACIO TO
SLIDE NORTH NORTHWESTWARD. TRACK GUIDANCE CONTINUES TO BE TIGHTLY
PACKED DEPICTING LITTLE CHANGE FROM LAST TIME. HOWEVER...THE
GUIDANCE ENVELOPE WIDENED SLIGHTLY AS HWRF SHIFTED RIGHT WHILE GFDL
SHIFTED LEFT. THE FORECAST TRACK WAS SHIFTED TO THE RIGHT THROUGH 48
HOURS TO ACCOUNT FOR THE RECENT SWING TO NORTH NORTHWEST MOTION. THE
REMAINING FORECAST TRACK CLOSELY FITS THE LAST ONE...REMAINING NEAR
THE LEFT EDGE OF THE GUIDANCE ENVELOPE AND CLOSELY FOLLOWING GFS.
THIS FORECAST TRACK CHANGE DECREASES 34 KT WIND ONSET PROBABILITIES
FOR LOCATIONS WITHIN TROPICAL STORM WATCHES...BUT ENOUGH FORECAST
UNCERTAINTY PERSISTS TO KEEP THESE WATCHES UP FOR NOW. A SMALL
SYSTEM MOTION CHANGE BACK TO THE NORTHWEST OR WEST NORTHWEST COULD
GREATLY INCREASE THESE PROBABILITIES.

SATELLITE LOOP SHOWS IGNACIO IS UNDERGOING INCREASING STRESS DUE TO
VERTICAL SHEAR. OUTFLOW REMAINS HINDERED TO THE NORTHWEST AND THE
DEEP CONVECTIVE CANOPY EROSION NOTED SINCE LAST EVENING IS
CONSISTENT WITH WEST TO WEST SOUTHWEST SHEAR. SHIPS INTENSITY
GUIDANCE SHOWS 10 TO 15 KT OF SHEAR NOW...WITH SHEAR IN EXCESS OF 20
KT FORECAST FROM 24 HOURS ONWARD. THIS LIKELY EXPLAINS SHIPS
DIMINISHING IGNACIO TO TROPICAL STORM STATUS BY 48 HOURS. IN
CONTRAST...GLOBAL MODELS AND GFDL KEEP THIS SYSTEM QUITE STRONG
THROUGH THE NEXT FIVE DAYS...WITH LITTLE WEAKENING. HWRF WEAKENS
IGNACIO...BUT NOT AS FAST AS SHIPS. OUR FORECAST CALLS FOR GRADUAL
WEAKENING...MAKING IGNACIO A TROPICAL STORM ON DAY FIVE...AS A BLEND
WITH SHIPS AND HWRF.

THE NEED FOR TROPICAL STORM WATCHES FOR THE BIG ISLAND AND THE
ISLANDS OF MAUI COUNTY WILL BE RE-EXAMINED ONCE AIRCRAFT DATA
BECOMES AVAILABLE LATER THIS MORNING.

FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 18.3N 148.4W 120 KT 140 MPH
12H 31/0000Z 19.1N 149.1W 110 KT 125 MPH
24H 31/1200Z 20.3N 150.5W 100 KT 115 MPH
36H 01/0000Z 21.4N 152.0W 90 KT 105 MPH
48H 01/1200Z 22.4N 153.6W 80 KT 90 MPH
72H 02/1200Z 24.3N 156.6W 70 KT 80 MPH
96H 03/1200Z 26.5N 159.9W 65 KT 75 MPH
120H 04/1200Z 28.7N 163.0W 60 KT 70 MPH

$$
FORECASTER POWELL
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#324 Postby Yellow Evan » Sun Aug 30, 2015 1:24 pm

WTPA33 PHFO 301806
TCPCP3

BULLETIN
HURRICANE IGNACIO INTERMEDIATE ADVISORY NUMBER 23A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
800 AM HST SUN AUG 30 2015

...MAJOR HURRICANE IGNACIO ABOUT 400 MILES EAST OF THE BIG ISLAND
AND TRACKING NORTH-NORTHWEST...


SUMMARY OF 800 AM HST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...18.6N 148.7W
ABOUT 420 MI...675 KM E OF HILO HAWAII
ABOUT 625 MI...1005 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...130 MPH...210 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...950 MB...28.05 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* MAUI COUNTY...INCLUDING THE ISLANDS OF MAUI...MOLOKAI...LANAI AND
KAHOOLAWE.
* HAWAII COUNTY

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS OF THE
INITIAL ISSUANCE.

INTERESTS ELSEWHERE IN THE MAIN HAWAIIAN ISLANDS SHOULD CONTINUE TO
CLOSELY MONITOR THE PROGRESS OF IGNACIO.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY THE NATIONAL WEATHER SERVICE OFFICE IN
HONOLULU HAWAII.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 AM HST...1800 UTC...THE CENTER OF HURRICANE IGNACIO WAS
LOCATED NEAR LATITUDE 18.6 NORTH...LONGITUDE 148.7 WEST. IGNACIO IS
MOVING TOWARD THE NORTH-NORTHWEST NEAR 9 MPH...15 KM/H...AND THIS
MOTION IS EXPECTED TO CONTINUE THROUGH TUESDAY. ON THE FORECAST
TRACK...THE CENTER OF IGNACIO IS EXPECTED TO PASS TO THE NORTHEAST
OF THE BIG ISLAND ON MONDAY...THEN NORTHEAST OF THE SMALLER ISLANDS
TUESDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 130 MPH...210 KM/H...WITH HIGHER
GUSTS. IGNACIO IS A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON
HURRICANE WIND SCALE. IGNACIO WILL WEAKEN THROUGH TUESDAY.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES...45 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 125
MILES...205 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 950 MB...28.05 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE ON THE BIG ISLAND
MONDAY NIGHT...AND TUESDAY ON MAUI.

RAINFALL...STORM TOTAL RAINFALL AMOUNTS OF 1 TO 3 INCHES...WITH
ISOLATED MAXIMUM AMOUNTS NEAR 5 INCHES MAINLY IN AREAS OF HIGHER
TERRAIN...ARE POSSIBLE IN THE WATCH AREA.

SURF...LARGE SWELLS GENERATED BY IGNACIO WILL ARRIVE ALONG EAST
AND SOUTHEAST FACING SHORES OF THE MAIN HAWAIIAN ISLANDS OVER THE
NEXT SEVERAL DAYS. RESULTANT SURF WILL BE LARGE AND POTENTIALLY
LIFE-THREATENING...ESPECIALLY ON THE BIG ISLAND LATER TODAY
AND EARLY NEXT WEEK.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 AM HST.

$$
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Re: EPAC: IGNACIO - Hurricane

#325 Postby supercane » Sun Aug 30, 2015 3:25 pm

Recon finds a weaker Ignacio. The 15 UTC advisory claimed MSW of 120kt and pressure of 948mb. The 18UTC intermediate advisory stated 130mph (115kt) and 950mb, respectively. The most recent VDM is below:

000
URPN12 KNHC 302010
VORTEX DATA MESSAGE EP122015
A. 30/19:50:40Z
B. 18 deg 45 min N
148 deg 59 min W
C. 700 mb 2764 m
D. 87 kt
E. 291 deg 7 nm
F. 018 deg 82 kt
G. 293 deg 9 nm
H. 961 mb
I. 13 C / 3055 m
J. 16 C / 3034 m
K. NA / NA
L. OPEN SW
M. C16
N. 12345 / 7
O. 0.02 / 1 nm
P. AF305 0412E IGNACIO OB 10
MAX FL WIND 107 KT 100 / 22 NM 18:16:50Z
MAX OUTBOUND FL WIND 91 KT 125 / 14 NM 19:55:00Z
CNTR DROPSONDE SFC WIND 180 / 8 KT
;

Given these data, any guesses for the upcoming 21Z advisory strength? The flight level winds and SFMR agree fairly well, so 90kt?
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#326 Postby Yellow Evan » Sun Aug 30, 2015 3:33 pm

:uarrow: Previous VDM was 107 knt FL 96 knt SFMR over the NE. Think 95 is still good.
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Re: EPAC: IGNACIO - Hurricane

#327 Postby supercane » Sun Aug 30, 2015 3:48 pm

When I pulled up the earlier VDM I saw 81, not 96kt for max SFMR wind. We'll find out in a few minutes, though.
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Re: EPAC: IGNACIO - Hurricane

#328 Postby Yellow Evan » Sun Aug 30, 2015 3:57 pm

supercane wrote:When I pulled up the earlier VDM I saw 81, not 96kt for max SFMR wind. We'll find out in a few minutes, though.


HDOB had a 96knt SFMR.
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Re: EPAC: IGNACIO - Hurricane

#329 Postby CrazyC83 » Sun Aug 30, 2015 3:59 pm

Yellow Evan wrote:
supercane wrote:When I pulled up the earlier VDM I saw 81, not 96kt for max SFMR wind. We'll find out in a few minutes, though.


HDOB had a 96knt SFMR.


That would likely support a 100 kt intensity.
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#330 Postby supercane » Sun Aug 30, 2015 4:12 pm

CrazyC83 wins. Latest advisory still has Ignacio as a minimal major hurricane. No changes in watches for now.

WTPA33 PHFO 302056
TCPCP3

BULLETIN
HURRICANE IGNACIO ADVISORY NUMBER 24
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 AM HST SUN AUG 30 2015

...RECONNAISSANCE AIRCRAFT FINDS IGNACIO WEAKER BUT STILL A MAJOR
HURRICANE FOR NOW...


SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.0N 149.0W
ABOUT 400 MI...645 KM E OF HILO HAWAII
ABOUT 600 MI...965 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...961 MB...28.38 INCHES

WTPA43 PHFO 302110
TCDCP3

HURRICANE IGNACIO DISCUSSION NUMBER 24
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 AM HST SUN AUG 30 2015

THE RECONNAISSANCE AIRCRAFT FOUND MAXIMUM FLIGHT LEVEL WINDS OF 107
KNOTS...A MAXIMUM SFMR WIND OF 94 KT...AND A 961 MB SURFACE
PRESSURE ON THE LAST PASS THROUGH THE EYE. THUS...HAVE LOWERED THE
INTENSITY OF IGNACIO TO 100 KT FOR THIS ADVISORY. THE UW-CIMSS SHEAR
ANALYSIS SHOWS IGNACIO IS NOW EXPERIENCING 15-20 KT OF SOUTHWESTERLY
SHEAR...WHICH IS CONFIRMED ON SATELLITE IMAGERY BY THE RESTRICTED
OUTFLOW IN THAT QUADRANT. RECENT MICROWAVE IMAGERY AND THE RECON
REPORTS SHOW THAT THE RING OF EYEWALL CONVECTION HAS OPENED UP...
AND THE EYE HAS NOW BECOME CLOUD-FILLED ON VISIBLE IMAGERY.

THE INITIAL MOTION IS 325/10. IGNACIO IS ABOUT TO GET ENTANGLED
WITH A WEAK BUT DIGGING UPPER LEVEL TROUGH OVER THE MAIN HAWAIIAN
ISLANDS WHICH WILL CONTINUE TO STEER THE TROPICAL CYCLONE TOWARD
THE NORTHWEST. THE FORECAST TRACK HAS BEEN ADJUSTED TO BE SLIGHTLY
MORE NORTHWARD IN THE SHORT TERM IN THE FACE OF INCREASING
SOUTHWESTERLIES...WITH A BEND BACK TOWARD THE NORTHWEST AFTER 24
HOURS AS IGNACIO BECOMES INCREASINGLY SHEARED. THIS IS A LITTLE TO
THE RIGHT OF THE GUIDANCE CONSENSUS THROUGH 24 HOURS...THEN SHIFTS
TO THE LEFT OF THE CONSENSUS GUIDANCE BY 48 HOURS AND BEYOND. LATE
IN THE FORECAST PERIOD...A STRONGER DIGGING MID-LATITUDE TROUGH FAR
TO THE NORTHWEST OF HAWAII IS EXPECTED TO STEER IGNACIO MORE
NORTHWARD AGAIN.

THE DYNAMIC MODELS SHOW SOUTHWESTERLY SHEAR WILL INCREASE RAPIDLY
OVER IGNACIO OVER THE NEXT 24-48 HOURS...AND THUS RAPID WEAKENING
IS EXPECTED. IT IS INTERESTING THAT IT HAS TAKEN THE SHIPS
STATISTICAL GUIDANCE THIS LONG TO INDICATE THE MAGNITUDE OF SHEAR AS
DEPICTED BY THE DYNAMICAL MODELS FOR A COUPLE OF DAYS NOW. IN ANY
CASE...THE FORECAST HAS BEEN ADJUSTED WEAKER AND IS NOW LOWER THAN
MOST OF THE GUIDANCE SUGGESTS. THE SHEAR MAY WEAKEN A BIT
TEMPORARILY DURING THE DAYS 4-5 TIME FRAME...BUT BY THEN IGNACIO
WILL BE MOVING OVER COOLER WATER.


FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 19.0N 149.0W 100 KT 115 MPH
12H 31/0600Z 20.0N 150.0W 85 KT 100 MPH
24H 31/1800Z 21.1N 151.1W 70 KT 80 MPH
36H 01/0600Z 22.1N 152.7W 55 KT 65 MPH
48H 01/1800Z 23.2N 154.2W 50 KT 60 MPH
72H 02/1800Z 24.9N 157.1W 45 KT 50 MPH
96H 03/1800Z 26.9N 160.2W 40 KT 45 MPH
120H 04/1800Z 30.0N 163.0W 40 KT 45 MPH

$$
FORECASTER R BALLARD
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#331 Postby Yellow Evan » Sun Aug 30, 2015 7:44 pm

WTPA33 PHFO 310005
TCPCP3

BULLETIN
HURRICANE IGNACIO INTERMEDIATE ADVISORY NUMBER 24A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
200 PM HST SUN AUG 30 2015

...MAJOR HURRICANE IGNACIO 360 MILES DUE EAST OF THE BIG
ISLAND AND CONTINUING TOWARD THE NORTHWEST...


SUMMARY OF 200 PM HST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...19.3N 149.3W
ABOUT 380 MI...610 KM E OF HILO HAWAII
ABOUT 575 MI...925 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...961 MB...28.38 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* MAUI COUNTY...INCLUDING THE ISLANDS OF MAUI...MOLOKAI...LANAI AND
KAHOOLAWE.
* HAWAII COUNTY

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS OF THE
INITIAL ISSUANCE.

INTERESTS ELSEWHERE IN THE MAIN HAWAIIAN ISLANDS SHOULD CONTINUE TO
CLOSELY MONITOR THE PROGRESS OF IGNACIO.


FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY THE NATIONAL WEATHER SERVICE OFFICE IN
HONOLULU HAWAII.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 PM HST...0000 UTC...THE EYE OF HURRICANE IGNACIO WAS
LOCATED BY U.S. AIR FORCE RECONNAISSANCE AIRCRAFT NEAR LATITUDE
19.3 NORTH...LONGITUDE 149.3 WEST. IGNACIO IS MOVING TOWARD THE
NORTHWEST NEAR 12 MPH...19 KM/H...AND THIS MOTION IS EXPECTED TO
CONTINUE FOR THE NEXT COUPLE OF DAYS. ON THE FORECAST TRACK...THE
CENTER OF IGNACIO WILL PASS APPROXIMATELY 200 MILES NORTHEAST OF THE
BIG ISLAND TUESDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 115 MPH...185 KM/H...WITH HIGHER
GUSTS. IGNACIO IS A CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON
HURRICANE WIND SCALE. WEAKENING IS EXPECTED FOR THE NEXT COUPLE OF
DAYS...AND IGNACIO MAY BECOME A TROPICAL STORM BY TUESDAY.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES...45 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 160
MILES...255 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 961 MB...28.38 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE ON THE BIG ISLAND
MONDAY NIGHT...AND TUESDAY ON MAUI.

RAINFALL...STORM TOTAL RAINFALL AMOUNTS OF 1 TO 3 INCHES...WITH
ISOLATED MAXIMUM AMOUNTS NEAR 5 INCHES MAINLY IN AREAS OF HIGHER
TERRAIN...ARE POSSIBLE IN THE WATCH AREA.

SURF...LARGE SWELLS GENERATED BY IGNACIO WILL ARRIVE ALONG EAST
AND SOUTHEAST FACING SHORES OF THE MAIN HAWAIIAN ISLANDS OVER THE
NEXT SEVERAL DAYS. RESULTANT SURF WILL BE LARGE AND POTENTIALLY
LIFE-THREATENING...ESPECIALLY ON THE BIG ISLAND LATER TODAY
AND EARLY NEXT WEEK.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 PM HST.

$$
FORECASTER R BALLARD
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Re: EPAC: IGNACIO - Hurricane

#332 Postby cycloneye » Sun Aug 30, 2015 10:41 pm

HURRICANE IGNACIO DISCUSSION NUMBER 25
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
500 PM HST SUN AUG 30 2015

THE LAST RECONNAISSANCE PASS THROUGH THE EYE OF IGNACIO MAINTAINED A
SURFACE PRESSURE OF 961 MB. ALTHOUGH THE MAXIMUM FLIGHT LEVEL WIND
WAS 99 KNOTS...THE SFMR PICKED UP WINDS OF 106 KT ON THE LAST PASS
THROUGH THE NORTHEAST QUADRANT. THE INTENSITY WILL BE KEPT TO 100 KT
FOR THIS ADVISORY. HOWEVER...SHEAR IS DEFINITELY STARTING TO TAKE A
TOLL ON IGNACIO AS THE SATELLITE AND MICROWAVE PRESENTATION
CONTINUES TO SLOWLY DEGRADE AS THE EYE BECOMES CLOUD-FILLED AND
INDISTINCT...THE EYEWALL IS OPEN AND DETERIORATING...AND SHEAR IS
RESTRICTING OUTFLOW IN THE SOUTHWEST QUADRANT.

THE INITIAL MOTION IS 325/10. THE HURRICANE WILL CONTINUE TO TRACK
TOWARD THE NORTHWEST...GENERALLY TOWARD A WEAK BUT DIGGING UPPER
LEVEL TROUGH NEAR THE MAIN HAWAIIAN ISLANDS. THE TRACK GUIDANCE
REMAINS FAIRLY TIGHTLY CLUSTERED. THE SLIGHTLY MORE NORTHWARD
MOTION OVER THE PAST 24 HOURS HAS CARRIED IGNACIO A LITTLE FARTHER
AWAY THAN FIRST EXPECTED...AND THUS WE ARE DISCONTINUING THE
TROPICAL STORM WATCH FOR MAUI COUNTY AND THE BIG ISLAND AT THIS
TIME. A SLIGHT BEND BACK TOWARD THE NORTHWEST IS STILL EXPECTED
AFTER 24 HOURS AS IGNACIO BECOMES INCREASINGLY SHEARED. A STRONGER
DIGGING MID-LATITUDE TROUGH WILL LIKELY PICK UP IGNACIO LATE IN THE
FORECAST PERIOD...PULLING IT NORTHWARD INTO THE MID-LATITUDES. OUR
FORECAST FOLLOWS CONSENSUS CLOSELY FOR THE FIRST 48 HOURS...THEN
TRENDS SLIGHTLY TO THE WEST OF THE CONSENSUS IN THE DAYS 3-5 TIME
FRAME ASSUMING A SYSTEM WEAKER THAN THE DYNAMICAL MODELS SUGGEST.

THE UW-CIMSS SHEAR ANALYSIS SHOWS 20-25 KNOTS OF SHEAR NOW
IMPACTING IGNACIO...AND THE SHEAR INCREASES EVEN MORE ALONG THE
FORECAST TRACK...SO IGNACIO/S HOURS AS A HURRICANE...MUCH LESS A
MAJOR ONE...ARE NUMBERED. THE INTENSITY FORECAST HAS NOT CHANGED...
SHOWING RAPID WEAKENING IN THE NEXT 48 HOURS WITH A MORE GRADUAL
WEAKENING EXPECTED THEREAFTER AS IGNACIO BECOMES A MORE SHALLOW
SYSTEM. THERE IS SOME INDICATION IN THE GLOBAL MODELS THAT THE SHEAR
MIGHT TEMPORARILY WEAKEN IN THE LONGER TIME RANGES...BUT BY THEN
IGNACIO WILL BE MOVING OVER THE SUB-27C SEA SURFACE TEMPERATURES AS
IT APPROACHES AND CROSSES LATITUDE 30N.


FORECAST POSITIONS AND MAX WINDS

INIT 31/0300Z 19.8N 149.6W 100 KT 115 MPH
12H 31/1200Z 20.8N 150.5W 85 KT 100 MPH
24H 01/0000Z 21.9N 151.8W 70 KT 80 MPH
36H 01/1200Z 23.0N 153.2W 60 KT 70 MPH
48H 02/0000Z 24.0N 154.6W 55 KT 65 MPH
72H 03/0000Z 25.9N 157.8W 50 KT 60 MPH
96H 04/0000Z 28.1N 161.4W 45 KT 50 MPH
120H 05/0000Z 32.0N 163.6W 45 KT 50 MPH

$$
FORECASTER R BALLARD
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#333 Postby 1900hurricane » Mon Aug 31, 2015 4:49 am

00Z ECMWF has fantasy-land off the rocker solution showing Ignacio turning west about 6 days from now and entering the WPac between 30-35*N as a still-identifiable system by day 9. We'll see, Ignacio might not even be around that long for all we know, but it could be something to watch for out of pure intrigue.
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#334 Postby Yellow Evan » Mon Aug 31, 2015 7:21 am

WTPA43 PHFO 310908 CCA
TCDCP3

HURRICANE IGNACIO DISCUSSION NUMBER 26
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 PM HST SUN AUG 30 2015

INFRARED SATELLITE IMAGES SHOW THAT IGNACIO CONTINUES TO STEADILY
WEAKEN...DOWN FROM A PEAK INTENSITY THAT WAS REACHED ABOUT 24 HOURS
AGO...WITH A CLOUD-FILLED EYE BARELY DISCERNIBLE. HURRICANE HUNTERS
FROM THE 53RD WEATHER RECONNAISSANCE SQUADRON ARE TRANSMITTING
OBSERVATIONS FROM THE HURRICANE THIS EVENING...PROVIDING GROUND
TRUTH AS TO THE CURRENT STATE OF IGNACIO. THESE OBSERVATIONS
INDICATE THAT THE HURRICANE IS CURRENTLY STRONGER THAN WHAT MIGHT
OTHERWISE BE INFERRED FROM THE SATELLITE DATA...AS THE CENTRAL
PRESSURE HAS INCREASED ONLY SLIGHTLY TO 963 MB. ADDITIONALLY...
MAXIMUM OBSERVED FLIGHT LEVEL WINDS WERE 114 KT IN THE NORTHEAST
QUADRANT...WHILE MAXIMUM UN-FLAGGED SFMR WINDS WERE NEAR 95 KT.
THESE OBSERVATIONS SUPPORT MAINTAINING THE CURRENT INTENSITY AT 100
KT FOR THIS ADVISORY. AIRCRAFT OBSERVATIONS ALSO INDICATE THAT AN
EYE STILL EXISTS...AND ALTHOUGH IT IS ELONGATED AND OPEN TO THE
SOUTHEAST...IT IS 45 NM WIDE ALONG THE LONG AXIS. THIS OBSERVATION
WAS NICELY CORROBORATED BY A 0459Z SSMI/S OVERPASS.

THE INITIAL MOTION VECTOR FOR THIS ADVISORY IS 325/8 KT. THE
FORECAST TRACK CALLS FOR IGNACIO TO MOVE GENERALLY NORTHWESTWARD
THROUGH THE NEXT 5 DAYS...INITIALLY UNDER THE INFLUENCE OF A
MID-LEVEL RIDGE CENTERED TO THE EAST-NORTHEAST. AS THE MID-LEVEL
PATTERN EVOLVES OVER THE NEXT 1 TO 3 DAYS...A DEVELOPING MID-LEVEL
RIDGE CENTERED FAR NORTH OF THE HAWAIIAN ISLANDS WILL KEEP THE
SYSTEM ON THIS GENERAL TRAJECTORY THROUGH THE FORECAST PERIOD. THE
LATEST ITERATION OF THE RELIABLE DYNAMICAL GUIDANCE IS TIGHTLY
CLUSTERED AROUND THE ONGOING TRACK FORECAST...THUS THE UPDATED
FORECAST OFFERS LITTLE CHANGE FROM THE PREVIOUS...AND IS VERY CLOSE
TO THE TVCN CONSENSUS.

IGNACIO IS WEAKENING IN THE FACE OF INCREASING SOUTHWESTERLY
SHEAR...ANALYZED AS BEING BETWEEN 20 AND 30 KT BY SHIPS GUIDANCE
AND UW-CIMSS...RESPECTIVELY. INCREASING SHEAR IS EXPECTED OVER THE
NEXT 2 DAYS OR SO...LEADING IGNACIO TO STEADILY WEAKEN TO A STRONG
TROPICAL STORM. THE SHEAR IS EXPECTED TO DIMINISH SOMEWHAT
AFTERWARD...AND ALTHOUGH UNDERLYING WATER TEMPERATURES WILL BE
DECREASING...THE UPDATED INTENSITY FORECAST ANTICIPATES A SLOWER
WEAKENING TREND TOWARD THE END OF THE FORECAST PERIOD. THIS IS LINE
WITH LATEST SHIPS GUIDANCE...AND FOLLOWS THE TREND PRESENTED BY THE
IVCN CONSENSUS.

WITH IGNACIO CONSIDERED TO BE A DIMINISHED THREAT TO THE MAIN
HAWAIIAN ISLANDS...THE NUMBER OF FUTURE RECONNAISSANCE FLIGHTS HAS
BEEN REDUCED...AND MAY BE DISCONTINUED COMPLETELY AFTER MONDAY.


FORECAST POSITIONS AND MAX WINDS

INIT 31/0900Z 20.3N 150.2W 100 KT 115 MPH
12H 31/1800Z 21.4N 151.1W 90 KT 105 MPH
24H 01/0600Z 22.5N 152.4W 75 KT 85 MPH
36H 01/1800Z 23.5N 153.8W 65 KT 75 MPH
48H 02/0600Z 24.5N 155.3W 60 KT 70 MPH
72H 03/0600Z 26.7N 158.7W 60 KT 70 MPH
96H 04/0600Z 29.0N 162.0W 60 KT 70 MPH
120H 05/0600Z 33.0N 163.5W 60 KT 70 MPH

$$

FORECASTER BIRCHARD
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Re: EPAC: IGNACIO - Hurricane

#335 Postby cycloneye » Mon Aug 31, 2015 10:24 pm

HURRICANE IGNACIO DISCUSSION NUMBER 29
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
500 PM HST MON AUG 31 2015

THE FINAL U.S. AIR FORCE RESERVE RECONNAISSANCE MISSION FOR IGNACIO
FOUND MAXIMUM FLIGHT LEVEL WINDS OF 100 KNOTS...AS WELL AS A MAXIMUM
SFMR WIND OF 83 KNOTS IN THE CONVECTIVELY ACTIVE NORTHWEST QUADRANT.
THE SURFACE PRESSURE HAD RISEN SEVERAL MILLIBARS FROM EARLY THIS
MORNING...UP TO 973 MB. BASED ON THESE DATA...HAVE LOWERED THE
ADVISORY INTENSITY SLIGHTLY TO 85 KT. THE HURRICANE IS TRAVERSING A
ZONE OF NEARLY 30 KNOTS OF SHEAR AS CALCULATED FROM THE LIHUE AND
HILO SOUNDINGS AND IN AGREEMENT WITH THE UW-CIMSS ANALYSIS. DESPITE
THIS...IGNACIO IS DOING ITS BEST TO FIGHT OFF THE EFFECTS OF THIS
SHEAR...AS THE AIRCRAFT STILL FOUND AN ELLIPTICAL 30 NM WIDE EYE ON
THE LONG AXIS. THE EYE WAS STILL FAINTLY DISCERNIBLE IN VISIBLE
IMAGERY LATE THIS AFTERNOON.

THE HURRICANE IS MOVING TOWARD THE NORTHWEST...310 DEGREES...AT 10
KT. THERE IS VERY LITTLE CHANGE TO THE FORECAST TRACK AS IGNACIO
HEADS NORTHWEST FOR THE NEXT FEW DAYS TOWARD A WEAK MID-LEVEL
TROUGH LOCATED TO THE NORTH OF FRENCH FRIGATE SHOALS. AFTER 3
DAYS...A TURN MORE TOWARD THE NORTH IS EXPECTED AS A STRONG
DIGGING MID-LATITUDE TROUGH BEGINS TO SCOOP UP IGNACIO. MOST OF THE
TRACK GUIDANCE REMAINS VERY TIGHTLY CLUSTERED ON OUR OFFICIAL
FORECAST THROUGH 5 DAYS...ALTHOUGH THE GFS IS A NOTEWORTHY OUTLIER
ON THE WEST SIDE OF THE GUIDANCE ENVELOPE BY DAY 3 AND BEYOND.

IGNACIO IS DOING A REMARKABLE JOB OF MAINTAINING AN INNER CORE IN
THE FACE OF THIS SHEAR. THIS MAY BE DUE TO THE ANOMALOUSLY WARM...2
TO 3C ABOVE NORMAL...SEA SURFACE TEMPERATURES IT IS CURRENTLY
TRAVERSING. THE MODERATE SOUTHWESTERLY SHEAR IS EXPECTED TO
CONTINUE ALONG THE FORECAST TRACK FOR THE NEXT 48 HOURS...LEADING
TO CONTINUED GRADUAL WEAKENING. AFTER THAT...IGNACIO MAY
TEMPORARILY WIND UP IN A ZONE OF WEAKER SHEAR WELL TO THE
NORTH-NORTHWEST OF HAWAII. AT DAYS 4 AND 5...IGNACIO MAY BEGIN TO
FEEL SOME BAROCLINIC INFLUENCE FROM THE EXTRATROPICAL TROUGH...AND
THE GLOBAL MODELS REFLECT THIS BY MAINTAINING IGNACIO AT HURRICANE
STRENGTH THROUGH THE END OF THE FORECAST PERIOD. HOWEVER...BY THEN
THE SYSTEM WILL BE OVER SEA SURFACE TEMPERATURES NEAR 24C AND SO
IT WILL VERY LIKELY START TO LOSE TROPICAL CHARACTERISTICS AT THAT
TIME. OUR FORECAST...WHICH IS SIMILAR TO THE PREVIOUS ADVISORY BUT
HAS A HIGH AMOUNT OF UNCERTAINTY...SHOWS SOMEWHAT MORE WEAKENING AND
IS MORE IN LINE WITH THE INTENSITY CONSENSUS.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 22.2N 152.3W 85 KT 100 MPH
12H 01/1200Z 23.0N 153.4W 80 KT 90 MPH
24H 02/0000Z 24.2N 154.9W 70 KT 80 MPH
36H 02/1200Z 25.1N 156.5W 65 KT 75 MPH
48H 03/0000Z 26.2N 158.1W 60 KT 70 MPH
72H 04/0000Z 28.8N 161.7W 60 KT 70 MPH
96H 05/0000Z 32.3N 163.5W 60 KT 70 MPH
120H 06/0000Z 37.3N 164.5W 60 KT 70 MPH

$$
R BALLARD
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#336 Postby 1900hurricane » Mon Aug 31, 2015 11:15 pm

I was wondering if/when they were going to address the solution shown by the GFS. Its idea of taking the storm NW/NNW to about 35*N and then abruptly turning it west and pushing it into the WPac is certainly a bizarre one. The ECMWF had been showing it too sometimes, even as recently as the old 00Z run, but the 12Z backed off on it. Either way, the end of Ignacio's life could offer up some intrigue.
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#337 Postby Yellow Evan » Mon Aug 31, 2015 11:21 pm

One thing that will keep this together is the very cold upper atmosphere at high latitudes. 24C with a cold upper atmosphere will allow this system to hold together.
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Re: EPAC: IGNACIO - Hurricane

#338 Postby cycloneye » Tue Sep 01, 2015 4:56 am

HURRICANE IGNACIO DISCUSSION NUMBER 30
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 PM HST MON AUG 31 2015

SHEAR IN EXCESS OF 25 KT IS DEFINITELY TAKING A TOLL ON IGNACIO THIS
EVENING...WITH AN INCREASINGLY ASYMMETRIC CANOPY AND A MORE RAGGED
OVERALL SATELLITE PRESENTATION SINCE THIS AFTERNOON. THE LLCC
POSITION HAS BECOME INCREASINGLY UNCERTAIN WITH THE EYE NO LONGER
DISCERNIBLE IN SATELLITE IMAGERY. THE DISPLACEMENT TO THE NORTHEAST
OF THE UPPER ROTATION...NOTED IN SATELLITE LOOP...FROM AN APPARENT
LLCC NOTED IN 0432 UTC SSMI MICROWAVE IMAGERY STRONGLY HINTS THAT
SHEAR IS FINALLY AFFECTING THE CORE OF THIS SYSTEM. SUBJECTIVE
DVORAK SATELLITE INTENSITY ESTIMATES RANGE FROM 4.0...65 KT...FROM
SAB TO 4.5...77 KT...FROM JTWC AND PHFO. WE WILL ASSIGN 75 KT AS THE
INITIAL INTENSITY FOR THIS ADVISORY...BLENDING CI ESTIMATES FROM THE
SATELLITE CENTERS WITH THE WORSENING SATELLITE PRESENTATION.

ASSUMING THAT THE CORE IS TILTED TOWARD THE NORTHEAST WITH HEIGHT
WITHIN STRONG SOUTHWEST SHEAR...IGNACIO IS MOVING TOWARD THE
NORTHWEST...325 DEGREES...AT 10 KT. THIS IS MORE NORTHERLY THAN THE
PREVIOUS MOTION AND DEVIATES NOTICEABLY TO THE RIGHT OF THE PREVIOUS
FORECAST TRACK. HOWEVER...AN ALTERNATIVE ASSUMPTION OF A STACKED
CORE WOULD HAVE RESULTED IN A MUCH LARGER DEVIATION. TRACK GUIDANCE
REMAINS TIGHTLY PACKED CARRYING IGNACIO GENERALLY TOWARD THE
NORTHWEST THROUGH DAY FIVE...WITH A SLIGHT SWING TO A MORE NORTHERLY
TRACK LATE IN THIS FORECAST PERIOD. THE FORECAST TRACK FOR THIS
ADVISORY WAS BUMPED TO THE RIGHT THROUGH 36 HOURS TO ACCOUNT FOR
INITIAL MOTION...THEN BLENDED BACK INTO THE CONSENSUS GUIDANCE
ENVELOPE AFTERWARDS. THIS TRACK WILL LIKELY BE ALTERED WITH THE NEXT
FEW ADVISORIES AS THE GLOBAL MODELS AND CONSENSUS GRAPPLE WITH HOW
IGNACIO WILL BE STEERED BY THE HIGH TO ITS DISTANT NORTHEAST AND THE
WEAK MID-LEVEL TROUGH TO ITS NORTHWEST.

IN SPITE OF THE HOSTILE SHEAR ENVIRONMENT...IGNACIO IS MOVING OVER
ANOMALOUSLY WARM WATER AND WILL CONTINUE TO DO SO THROUGH AT LEAST
48 HOURS. THIS IS REFLECTED IN INTENSITY GUIDANCE...WHICH IS QUITE
HESITANT TO WEAKEN THIS SYSTEM TOO FAST. OUR FORECAST CALLS FOR
IGNACIO TO VERY GRADUALLY WEAKEN BUT REMAIN AT HURRICANE STRENGTH
THROUGH 36 HOURS. CONTINUED WEAKENING IS THEN EXPECTED THROUGH THE
FORECAST PERIOD AS IGNACIO BEGINS TO FEEL MID-LATITUDE BAROCLINIC
EFFECTS. FOR THIS GUIDANCE PACKAGE...ONLY ECMWF KEEPS THIS SYSTEM AT
HURRICANE STRENGTH THROUGH 120 HOURS. THE FORECAST WEAKENING TREND
MIRRORS THE PREVIOUS ONE AFTER 48 HOURS...KEEPING WHATEVER IS LEFT
OF IGNACIO WITHIN TROPICAL STORM STRENGTH RANGE ON DAY FIVE.

FORECAST POSITIONS AND MAX WINDS

INIT 01/0900Z 23.1N 152.3W 75 KT 85 MPH
12H 01/1800Z 24.2N 153.4W 70 KT 80 MPH
24H 02/0600Z 25.4N 154.8W 65 KT 75 MPH
36H 02/1800Z 26.5N 156.4W 65 KT 75 MPH
48H 03/0600Z 27.8N 158.2W 60 KT 70 MPH
72H 04/0600Z 30.6N 161.3W 60 KT 70 MPH
96H 05/0600Z 34.6N 163.4W 60 KT 70 MPH
120H 06/0600Z 38.8N 164.4W 50 KT 60 MPH

$$
FORECASTER POWELL
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Re: EPAC: IGNACIO - Hurricane

#339 Postby cycloneye » Tue Sep 01, 2015 10:08 am

HURRICANE IGNACIO DISCUSSION NUMBER 31
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
500 AM HST TUE SEP 01 2015

THE SHEARED CORE ASSUMPTION MADE WITH THE LAST ADVISORY WAS CORRECT.
HOWEVER...IT TURNS OUT THAT THE EARLIER CDO CLOUD SWIRL FAVORED BY
THE SATELLITE CENTERS AT 0600 UTC WAS MORE SHEARED TO THE NORTHEAST
OF THE LLCC THAN ANTICIPATED. THE CDO HAS NOW BEEN COMPLETELY
SHEARED AWAY AND REPLACED WITH A WARMER BANDING FEATURE ACROSS THE
WESTERN AND NORTHERN SEMICIRCLES. THIS IS A WEAKER SATELLITE
PRESENTATION THAN LAST TIME...AND WE ARE NOT SURPRISED BY THE LOWER
INTENSITY NUMBERS RECEIVED FROM THE SATELLITE CENTERS. SUBJECTIVE
DVORAK INTENSITY ESTIMATES WERE ALL 4.0...65 KT. UW-CIMSS ADT WAS
4.3...72 KT. GIVEN THE CONTINUED DEGRADED APPEARANCE OF THIS
SYSTEM...WE WILL ASSIGN AN INITIAL INTENSITY OF 70 KT FOR THIS
ADVISORY.

A WELL-PLACED 0744 UTC ASCAT PASS...RECEIVED TOO LATE TO HELP LAST
TIME...SHOWED THAT THE LLCC HAS MAINTAINED A STEADY MOTION OF 315/09
KT OVER THE PAST 12 HOURS. AN 0743 UTC AMSU PASS SEEMS TO CONFIRM
THIS AS WELL AS A REANALYZED 0432 UTC SSMI PASS...WHICH HAS SINCE
BEEN EDITED IN THE FIX RECORD. THE 0600 UTC BEST TRACK POSITION HAS
BEEN REANALYZED AND REBESTED AS WELL. TRACK GUIDANCE REMAINS TIGHTLY
PACKED CARRYING IGNACIO GENERALLY TOWARD THE NORTHWEST THROUGH DAY
FIVE...WITH A SLIGHT SWING TO A MORE NORTHERLY TRACK LATE IN THIS
FORECAST PERIOD. HOWEVER...ALMOST ALL GUIDANCE SHIFTED TO THE
LEFT...MAKING EVEN THE REANALYZED MOTION TOO FAR TO THE RIGHT TO
KEEP THE SHORT TERM FORECAST TRACK WITHIN THE GUIDANCE ENVELOPE. THE
FORECAST TRACK FOR THIS ADVISORY THEREFORE KEEPS ITS INITIAL BUMP TO
THE RIGHT OF GUIDANCE TO ACCOUNT FOR INITIAL MOTION...THEN IS
ALTERED TO THE LEFT JUST ENOUGH AFTER 24 HOURS TO BLEND BACK INTO
THE ENVELOPE TO FOLLOW THE CURVE OF CONSENSUS GUIDANCE. THESE TRACK
ADJUSTMENTS WILL LIKELY OCCUR FOR THE NEXT FEW ADVISORIES AS THE
GLOBAL MODELS AND CONSENSUS GRAPPLE WITH HOW IGNACIO WILL BE STEERED
BY THE HIGH TO ITS DISTANT NORTHEAST AND THE WEAK MID-LEVEL TROUGH
TO ITS NORTHWEST.

INTENSITY GUIDANCE CONTINUES TO FAVOR VERY SLOW WEAKENING THROUGH
DAY FIVE...WITH IGNACIO STILL A TROPICAL STORM AT THE END OF THIS
PERIOD. HOWEVER...IGNACIO SHOULD BE PASSING OVER 23 TO 24 DEGREE
CELSIUS WATER AND APPROACHING 40N LATITUDE BY THE END OF THE
FORECAST PERIOD...SO THIS SYSTEM MAY BEGIN TO LOSE TROPICAL
CHARACTERISTICS BY THEN AND START EXTRATROPICAL TRANSITION. SHEAR
ACTUALLY DECREASES ALONG THE TRACK...BELOW 20 KT BETWEEN 36 AND 72
HOURS...AND THIS MAY ACCOUNT FOR GUIDANCE DEPICTION OF A LONGER
SYSTEM LIFE. SHIPS GUIDANCE SHOWS THE INTENSITY CHANGE CONTRIBUTIONS
FOR SHEAR DIRECTION AND SHEAR MAGNITUDE ALMOST CANCELLING EACH OTHER
OUT THROUGH 96 HOURS. ANYWAY...WE WILL FOLLOW THE SLOW WEAKENING
TREND FROM THE LAST ADVISORY AFTER ADJUSTING FOR THE LOWER INITIAL
INTENSITY.

FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 23.5N 153.7W 70 KT 80 MPH
12H 02/0000Z 24.4N 154.7W 65 KT 75 MPH
24H 02/1200Z 25.5N 156.3W 65 KT 75 MPH
36H 03/0000Z 26.5N 157.9W 65 KT 75 MPH
48H 03/1200Z 27.6N 159.7W 60 KT 70 MPH
72H 04/1200Z 30.6N 162.9W 60 KT 70 MPH
96H 05/1200Z 34.2N 165.3W 60 KT 70 MPH
120H 06/1200Z 38.1N 167.2W 50 KT 60 MPH

$$
FORECASTER POWELL
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Re: EPAC: IGNACIO - Hurricane

#340 Postby cycloneye » Tue Sep 01, 2015 4:08 pm

HURRICANE IGNACIO DISCUSSION NUMBER 32
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 AM HST TUE SEP 01 2015

DEEP CONVECTION CONTINUES TO SPUTTER AROUND THE NORTHWEST AND NORTH
SIDE OF THE CORE OF IGNACIO IN THE FACE OF ABOUT 25 TO 30 KNOTS OF
SOUTHWESTERLY SHEAR AS ANALYZED BY BOTH UW-CIMSS AND THE 1800 UTC
SPECIAL SOUNDINGS FROM LIHUE AND HILO. SPIRAL RAINBANDS...AS WELL
AS SOME OF THE CORE STRUCTURE OF THE HURRICANE...CAN BE DISCERNED BY
THE MOLOKAI WEATHER RADAR THIS MORNING. THE DVORAK INTENSITY
ESTIMATES WERE A UNANIMOUS 4.0 FROM THE SATELLITE FIX AGENCIES FOR
THIS ADVISORY...SO THE INITIAL INTENSITY WILL BE SET TO 65 KT.

IGNACIO CONTINUES TO BEHAVE ITSELF AS IT PASSES BY THE MAIN HAWAIIAN
ISLANDS NOT FAR TO OUR NORTHEAST. THE INITIAL MOTION REMAINS TOWARD
THE NORTHWEST...310 DEGREES...AT ABOUT 9 KNOTS. THERE IS STILL NO
CHANGE TO THE FORECAST PHILOSOPHY AS IGNACIO IS EXPECTED TO HEAD
TOWARD THE NORTHWEST FOR THE NEXT 2 DAYS TOWARD A WEAKNESS IN A
MID-LEVEL RIDGE TO THE NORTH OF FRENCH FRIGATE SHOALS. A TURN MORE
TOWARD THE NORTH IS EXPECTED ON DAY 3 AS THE TROPICAL CYCLONE HEADS
FOR THE MID-LATITUDES AND GETS ABSORBED BY A LONGWAVE TROUGH.

THE INTENSITY FORECAST IS QUITE CHALLENGING. IF IGNACIO CAN MAINTAIN
ENOUGH DEEP CONVECTION TO STILL BE CLASSIFIABLE AS A TROPICAL
CYCLONE THROUGH THE NEXT 36-48 HOURS...THE SHEAR WILL RELAX AND THE
CORE WILL STILL BE OVER SEA SURFACE TEMPERATURES JUST OVER 27C. OUR
INTENSITY FORECAST SHOWS ONLY A VERY SLOW WEAKENING TREND THROUGH
THE PERIOD...BUT THERE ARE ALTERNATE POSSIBILITIES THAT IGNACIO
EITHER WILL NOT LAST THAT LONG...OR IF IT DOES...IT COULD BRIEFLY
REINTENSIFY. AT DAYS 4 AND 5...THE CYCLONE IS LIKELY TO START
EXPERIENCING EXTRATROPICAL TRANSITION OVER THE COOLER WATERS OF THE
NORTH PACIFIC. THE INTENSITY FORECAST IS SIMILAR TO THE INTENSITY
CONSENSUS GUIDANCE...BUT SLIGHTLY HIGHER AT DAYS 4 AND 5 WHICH
IS MORE IN LINE WITH THE DYNAMICAL MODELS.

THE FORECAST WIND RADII WERE ADJUSTED A BIT BASED ON AN 0744 UTC
ASCAT PASS.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 23.8N 154.5W 65 KT 75 MPH
12H 02/0600Z 24.5N 155.9W 65 KT 75 MPH
24H 02/1800Z 25.8N 157.9W 65 KT 75 MPH
36H 03/0600Z 27.2N 160.0W 65 KT 75 MPH
48H 03/1800Z 28.4N 161.9W 60 KT 70 MPH
72H 04/1800Z 31.7N 164.2W 60 KT 70 MPH
96H 05/1800Z 35.3N 165.7W 60 KT 70 MPH
120H 06/1800Z 39.3N 167.8W 55 KT 65 MPH

$$
FORECASTER R BALLARD
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