EPAC: MIRIAM - Post-Tropical

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#61 Postby Yellow Evan » Sun Sep 23, 2012 9:27 am

This should be a hurricane by tonight.
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Re: EPAC: MIRIAM - Tropical Storm

#62 Postby cycloneye » Sun Sep 23, 2012 9:58 am

BULLETIN
TROPICAL STORM MIRIAM ADVISORY NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012
800 AM PDT SUN SEP 23 2012

...MIRIAM STRENGTHENING...
...FORECAST TO BECOME A HURRICANE TONIGHT...


SUMMARY OF 800 AM PDT...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...15.6N 109.6W
ABOUT 505 MI...810 KM S OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...996 MB...29.41 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 MIRIAM WAS
LOCATED NEAR LATITUDE 15.6 NORTH...LONGITUDE 109.6 WEST. MIRIAM IS
MOVING TOWARD THE NORTHWEST NEAR 8 MPH...13 KM/H. THIS GENERAL
MOTION WITH A GRADUAL DECREASE IN FORWARD SPEED IS EXPECTED TO
CONTINUE FOR THE NEXT COUPLE OF DAYS.

MAXIMUM SUSTAINED WINDS HAVE INCREASED TO NEAR 65 MPH...100
KM/H...WITH HIGHER GUSTS. ADDITIONAL STRENGTHENING IS FORECAST
DURING THE NEXT DAY OR SO...AND MIRIAM IS EXPECTED TO BECOME A
HURRICANE TONIGHT.

TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB...29.41 INCHES.


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


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

$$
FORECASTER KIMBERLAIN

TROPICAL STORM MIRIAM DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012
800 AM PDT SUN SEP 23 2012

SATELLITE IMAGERY INDICATES THAT THE CLOUD PATTERN OF MIRIAM
CONTINUES TO INCREASE IN ORGANIZATION. A COMPACT CENTRAL DENSE
OVERCAST HAS FORMED AND BECOME BETTER DEFINED DURING THE PAST 6-12
HOURS. THERE IS ALSO PLENTY OF COLD-TOPPED CONVECTION ASSOCIATED
WITH THE CYCLONE...AND BANDING HAS BEEN INCREASING. DVORAK
T-NUMBERS HAVE INCREASED TO 3.5 FROM TAFB AND SAB...AND UW-CMSS ADT
CI VALUES ARE AT 3.6. BASED ON THESE DATA...THE INITIAL INTENSITY
IS RAISED TO 55 KT.

THE INITIAL MOTION ESTIMATE IS 305/07. THE CYCLONE IS FORECAST TO
MAINTAIN THIS GENERAL MOTION DURING THE NEXT DAY OR SO AS IT TURNS
AROUND THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE LOCATED
OVER NORTHERN MEXICO. BY 48 HOURS...MIRIAM SHOULD ENCOUNTER A
WEAKNESS ALONG 115W AS A LONGWAVE TROUGH DEVELOPS OVER THE WESTERN
UNITED STATES. THIS PATTERN SHOULD RESULT IN A GRADUAL NORTHWARD
TURN AND A SLOWING OF THE FORWARD MOTION DURING THE 3 TO 5 DAY
PERIOD. THERE REMAINS A NOTABLE SPLIT IN THE GUIDANCE AFTER
72 HOURS...PARTIALLY DUE TO THE DEGREE OF INTERACTION OF MIRIAM
WITH A CUT-OFF LOW FORECAST TO DEVELOP WEST OF THE CYCLONE IN ABOUT
4 DAYS. THE NHC FORECAST HAS SHIFTED TOWARD THE EAST...FOLLOWING
THE MULTI-MODEL CONSENSUS TVCE. THE OFFICIAL FORECAST ALSO REMAINS
ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE...BUT NOT AS FAR EAST AS
THE ECMWF/GFS SOLUTIONS.

MIRIAM SHOULD BE MOVING THROUGH AN ENVIRONMENT OF WARM SSTS...A VERY
MOIST MID-TROPOSPHERE...AND LOW SHEAR DURING THE NEXT DAY OR SO.
THE SHIPS RAPID INTENSIFICATION INDEX RESPONDS TO THESE FAVORABLE
PARAMETERS BY SHOWING A 75% CHANCE OF A 30 KT INCREASE IN STRENGTH
DURING THE NEXT 24 HOURS. BY 72 HOURS...MIRIAM SHOULD BE NORTH OF
THE UPPER-LEVEL RIDGE AXIS AND EXPERIENCE AN INCREASE IN WESTERLY
SHEAR ALONG WITH GRADUALLY DECREASING SSTS. WEAKENING IS EXPECTED
AT THAT TIME...BUT THE RATE OF WEAKENING SEEMS DEPENDENT ON THE
EXACT TRACK OF THE CYCLONE AS WELL AS ITS POTENTIAL INTERACTION
WITH THE AFORMENTIONED CUT-OFF LOW. A TRACK FARTHER EAST COULD KEEP
MIRIAM OVER WARMER WATER LONGER AND AWAY FROM EVEN STRONGER SHEAR
CONDITIONS ASSOCIATED WITH THE CUT-OFF LOW. THE NHC INTENSITY
FORECAST IS INCREASED A BIT IN THE SHORT TERM RELATIVE TO THE
PREVIOUS ONE BUT IS CLOSE TO THE INTENSITY CONSENSUS AIDS.


FORECAST POSITIONS AND MAX WINDS

INIT 23/1500Z 15.6N 109.6W 55 KT 65 MPH
12H 24/0000Z 16.5N 110.8W 70 KT 80 MPH
24H 24/1200Z 17.6N 112.4W 85 KT 100 MPH
36H 25/0000Z 18.5N 113.7W 85 KT 100 MPH
48H 25/1200Z 19.0N 114.5W 80 KT 90 MPH
72H 26/1200Z 20.2N 115.5W 70 KT 80 MPH
96H 27/1200Z 21.4N 116.0W 55 KT 65 MPH
120H 28/1200Z 22.5N 116.0W 40 KT 45 MPH

$$
FORECASTER KIMBERLAIN
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#63 Postby Ntxw » Sun Sep 23, 2012 10:36 am

Image

Certainly is compacting.
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#64 Postby Yellow Evan » Sun Sep 23, 2012 10:59 am

Nearly a hurricane IMO.
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#65 Postby brunota2003 » Sun Sep 23, 2012 11:09 am

The NHC is actually forecasting an episode of RI? Wow
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Re:

#66 Postby Weatherguy173 » Sun Sep 23, 2012 11:15 am

brunota2003 wrote:The NHC is actually forecasting an episode of RI? Wow


well as of now it seems to be organizing rather quickly, pretty cool
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#67 Postby Kingarabian » Sun Sep 23, 2012 1:12 pm

The eye wall is getting better organized. Could take off from here.
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Re: EPAC: MIRIAM - Tropical Storm

#68 Postby cycloneye » Sun Sep 23, 2012 1:29 pm

18z Best Track.

EP, 13, 2012092318, , BEST, 0, 158N, 1101W, 55, 996, TS
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Re: EPAC: MIRIAM - Tropical Storm

#69 Postby cycloneye » Sun Sep 23, 2012 2:14 pm

ATCF updates the 18z Best Track to increase winds,now at 60kts.

EP, 13, 2012092318, , BEST, 0, 158N, 1101W, 60, 994, TS
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#70 Postby Kingarabian » Sun Sep 23, 2012 2:28 pm

Image

Weak EW but it's there.
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#71 Postby Yellow Evan » Sun Sep 23, 2012 3:09 pm

Should be a hurricane by tonight.
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Re: EPAC: MIRIAM - Tropical Storm

#72 Postby cycloneye » Sun Sep 23, 2012 3:36 pm

TROPICAL STORM MIRIAM DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL EP132012
200 PM PDT SUN SEP 23 2012

MIRIAM APPEARS TO BE GRADUALLY STRENGTHENING. THE CYCLONE IS
MAINTAINING A CENTRAL DENSE OVERCAST WITH COLD CLOUD TOP
TEMPEATURES. A 1554 UTC SSMIS PASS SHOWED A DEVELOPING MID-LEVEL
EYE...AND A CLOSED LOW-LEVEL RING OF CONVECTION WAS EVIDENT IN AN
EARLIER WINDSAT PASS. IN ADDITION...TIGHTLY COILED BANDS DOMINATE
THE OUTER CIRCULATION OF THE CYCLONE. DVORAK T-NUMBERS ARE AT 3.5
AND 4.0 FROM TAFB AND SAB...RESPECTIVELY...AND UW-CIMSS ADT CI
VALUES ARE AT 4.4. BASED ON A BLEND OF THE ABOVE DATA...THE
INITIAL INTENSITY ESTIMATE IS RAISED TO 60 KT.

SATELLITE AND MICROWAVE DATA SUGGEST THAT THE HEADING HAS BEEN
SLIGHTLY TO THE LEFT OF THE PREVIOUS ESTIMATE. A LONGER-TERM
AVERAGE OF FIXES SUGGESTS AN INITIAL MOTION ESTIMATE OF 300/08.
GLOBAL MODELS SHOW CONTINUING WEST-NORTHWEST TO NORTHWEST MOTION AS
MIRIAM ROUNDS THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE OVER
NORTHERN MEXICO DURING THE NEXT 36 HOURS. A GRADUAL TURN TOWARD
THE NORTH-NORTHWEST AND NORTH ARE EXPECTED FROM 48-96 HOURS AS
MIRIAM MOVES INTO A WEAKNESS ALONG 115W...CREATED BY A SHORTWAVE
TROUGH PASSING THROUGH THE WESTERN UNITED STATES. THE LATTER PART
OF THE FORECAST PARTIALLY HINGES ON THE DEGREE OF INTERACTION WITH A
MID- TO UPPER-LEVEL TROUGH FORECAST TO FORM WEST OR NORTHWEST OF
MIRIAM. THE SPREAD IN THE GUIDANCE IS STILL RATHER SIGNIFICANT...
ESPECIALLY BEYOND 96 HOURS...BUT LITTLE CHANGE IS NOTED BETWEEN
THIS CYCLE AND THE PREVIOUS ONE. THE NHC TRACK FORECAST IS
ESSENTIALLY AN UPDATE OF THE PREVIOUS ONE...AND IS ON THE RIGHT
SIDE OF THE GUIDANCE ENVELOPE...CLOSEST TO THE ECMWF/GFS SOLUTIONS.

MIRIAM IS EXPECTED TO REMAIN IN A FAVORABLE ENVIROMENT FOR
STRENGTHENING DURING THE NEXT 24 HOURS...AND THE RATE OF
INTENSIFICATION COULD POTENTIALLY BE RAPID AS INDICATED BY THE
SHIPS RI INDEX. IN 2-3 DAYS...MIRIAM SHOULD CROSS THE UPPER-LEVEL
RIDGE AXIS AND SHOULD ALSO INTERACT WITH A SHORTWAVE TROUGH DIVING
SOUTHEASTWARD TOWARD THE CYCLONE. AN INCREASE IN SHEAR RELATED TO
THE ABOVE FACTORS AND GRADUALLY DECREASING SSTS SHOULD PROMOTE
WEAKENING. THE WEAKENING SHOULD CONTINUE DURING THE 3 TO 5 DAY
PERIOD...WITH EVEN THE POSSIBILITY OF MIRIAM DECOUPLING ENTIRELY AS
DEPICTED BY ECMWF. A CRITICAL ELEMENT OF THE INTENSITY FORECAST
COULD BE THE LONGITUDE WHERE MIRIAM TURNS NORTHWARD...SINCE THE
EXACT TRACK OF THE CYCLONE WITH RESPECT TO A STRONG GRADIENT IN
SSTS COULD DETERMINE HOW QUICKLY THE CYCLONE WEAKENS. THE NHC
INTENSITY FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS AND IS IN
GOOD AGREEMENT WITH THE LATEST INTENSITY CONSENSUS AIDS.

FORECAST POSITIONS AND MAX WINDS

INIT 23/2100Z 16.1N 110.5W 60 KT 70 MPH
12H 24/0600Z 16.8N 111.8W 75 KT 85 MPH
24H 24/1800Z 17.9N 113.4W 85 KT 100 MPH
36H 25/0600Z 18.7N 114.5W 85 KT 100 MPH
48H 25/1800Z 19.4N 115.2W 80 KT 90 MPH
72H 26/1800Z 20.7N 115.9W 60 KT 70 MPH
96H 27/1800Z 22.3N 116.0W 45 KT 50 MPH
120H 28/1800Z 23.5N 116.0W 35 KT 40 MPH

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

#73 Postby Macrocane » Sun Sep 23, 2012 6:21 pm

It has an amazing structure, the one you see usually on rapidly intensifying tropical cyclones, it would be interesting to see how much it can intensify, especially overnight with the help of Dmax.
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Re: EPAC: MIRIAM - Tropical Storm

#74 Postby Yellow Evan » Sun Sep 23, 2012 6:31 pm

Macrocane wrote:It has an amazing structure, the one you see usually on rapidly intensifying tropical cyclones, it would be interesting to see how much it can intensify, especially overnight with the help of Dmax.


AFAIK DMAX only affects weak storms.
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Re: EPAC: MIRIAM - Tropical Storm

#75 Postby cycloneye » Sun Sep 23, 2012 7:36 pm

She may be doing RI now.

24/0000 UTC 16.6N 110.9W T4.5/4.5 MIRIAM -- East Pacific
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Re: EPAC: MIRIAM - Tropical Storm

#76 Postby cycloneye » Sun Sep 23, 2012 7:44 pm

cycloneye wrote:She may be doing RI now.

24/0000 UTC 16.6N 110.9W T4.5/4.5 MIRIAM -- East Pacific


00z Best Track confirms the RI.

EP, 13, 2012092400, , BEST, 0, 165N, 1109W, 75, 983, HU

ftp://ftp.nhc.noaa.gov/atcf/tcweb/inves ... 012.invest
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Re: EPAC: MIRIAM - Tropical Storm

#77 Postby Macrocane » Sun Sep 23, 2012 7:45 pm

Yellow Evan wrote:

AFAIK DMAX only affects weak storms.


Thanks! didn't know that! Anyway it is rapidly intensifying, 75 kt now and eye appearing.
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#78 Postby Kingarabian » Sun Sep 23, 2012 8:01 pm

Really looks like she's going into RI. To bad the sun is setting.
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#79 Postby Kingarabian » Sun Sep 23, 2012 9:16 pm

Final T# Adj T# Raw T#
4.7 4.7 5.9
RI
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#80 Postby Yellow Evan » Sun Sep 23, 2012 9:27 pm

Go Miriam Go!
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