EPAC : TROPICAL DEPRESSION DARBY - DISCUSSION

[cycloneye]

TCDEP5
TROPICAL STORM DARBY DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052010
200 AM PDT WED JUN 23 2010

THE OVERALL CONVECTIVE STRUCTURE OF THE TROPICAL CYCLONE HAS
CONTINUED TO BECOME MORE ORGANIZED. ALTHOUGH THE CIRCULATION
CENTER APPEARS TO BE LOCATED ON THE WESTERN EDGE OF THE DEEP
CONVECTION DUE TO SOME EASTERLY SHEAR...DVORAK T-NUMBERS ARE 2.5
FROM TAFB AND 2.0 FROM SAB. ASCAT DATA...WHICH IS KNOWN TO HAVE A
LOW BIAS...SHOWED A MAXIMUM OF 30 KT OUTSIDE OF THE DEEP CONVECTION
AT 0306 UTC. SINCE THE CLOUD PATTERN HAS IMPROVED OVER THE PAST
FEW HOURS AND STRONGER WINDS ARE LIKELY OCCURRING IN THE DEEP
CONVECTION...THE DEPRESSION IS UPGRADED TO TROPICAL STORM DARBY.

THE ASCAT PASS HELPED IN LOCATING THE LOW-LEVEL CENTER...AND IT IS
ESTIMATED THAT DARBY IS MOVING 305 DEGREES AT 8 KNOTS. A MID-LEVEL
RIDGE LOCATED OVER THE SOUTHERN UNITED STATES AND MEXICO SHOULD
STEER DARBY GENERALLY TOWARD THE WEST-NORTHWEST OVER THE NEXT 2
DAYS. THEREAFTER...STEERING CURRENTS ARE EXPECTED TO WEAKEN AS THE
RIDGE BREAKS DOWN. IN FACT...SEVERAL GLOBAL MODELS SUGGEST THAT
DARBY COULD STOP ALTOGETHER AND ATTAIN SOME EASTWARD MOTION WITHIN
LOW-LEVEL SOUTHWESTERLY FLOW DURING THAT TIME. THE GLOBAL MODEL
SOLUTIONS ARE COUNTER TO THAT OF THE GFDL AND HWRF...WHICH MAINTAIN
A SLOW WEST-NORTHWESTWARD MOTION THROUGH THE FORECAST PERIOD. THIS
UNCERTAINTY SUPPORTS THE NEGLIGIBLE MOTION SHOWN IN THE OFFICIAL
FORECAST BY DAY 5.

THE SHIPS MODEL INDICATES THAT THE EASTERLY SHEAR OVER DARBY SHOULD
ABATE OVER THE NEXT 2 DAYS...GIVING THE SYSTEM A CHANCE TO
INTENSIFY. THE NEW OFFICIAL FORECAST SHOWS A LITTLE MORE
STRENGTHENING THAN THE PREVIOUS FORECAST...BUT THIS STILL MIGHT BE
ON THE CONSERVATIVE SIDE SINCE THE SHIPS RI INDEX INDICATES A 1 IN
4 CHANCE OF RAPID INTENSIFICATION OVER THE NEXT 24 HOURS. WHATEVER
THE MAXIMUM INTENSITY...INCREASED VERTICAL SHEAR AFTER DAY 3 IS
EXPECTED TO INDUCE WEAKENING...ESPECIALLY IF DARBY BEGINS TO ATTAIN
AN EASTERLY MOTION.


FORECAST POSITIONS AND MAX WINDS

INITIAL 23/0900Z 11.5N 94.0W 35 KT
12HR VT 23/1800Z 11.9N 95.1W 40 KT
24HR VT 24/0600Z 12.4N 96.6W 45 KT
36HR VT 24/1800Z 12.8N 98.2W 50 KT
48HR VT 25/0600Z 13.0N 99.4W 55 KT
72HR VT 26/0600Z 13.5N 101.0W 55 KT
96HR VT 27/0600Z 14.0N 101.5W 50 KT
120HR VT 28/0600Z 14.5N 101.5W 45 KT

$$
FORECASTER BERG

[KWT]

Amazing start in the EPAC...I suspect the fact the Atl is so energetic so early gives the waves an extra boost before they reach the EPAC, which gives them a headstart.

Looks like this one may well end up making landfall as it follows the weakness created by 93L.

[HURAKAN]

Latest

[HURAKAN]

45 knots

[CrazyC83]

Looks to be rapidly intensifying with an eye forming. I'd say more like 50-55 kt, with Hurricane Darby around the corner.

[HURAKAN]

TROPICAL STORM DARBY DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052010
800 AM PDT WED JUN 23 2010

THE CONVECTIVE ORGANIZATION OF DARBY HAS INCREASED SHARPLY DURING
THE PAST 6 HOURS AS STRONGLY CURVED BANDING FEATURES HAVE
DEVELOPED. IN FACT...RECENT VISIBLE SATELLITE IMAGES HINT THAT A
BANDING EYE FEATURE COULD BE FORMING...BUT THIS MAY JUST BE A SMALL
DRY SLOT THAT HAS DEVELOPED. INTENSITY ESTIMATES ARE T3.0 FROM TAFB
AND T2.5 FROM SAB. GIVEN THE IMPROVED SATELLITE APPEARANCE SINCE
THE 12Z FIXES...THE INITIAL INTENSITY IS SET AT 45 KT.

THE INITIAL MOTION ESTIMATE IS 285/08. THE FORECAST TRACK OF DARBY
HINGES HEAVILY UPON WHAT HAPPENS TO THE DISTURBANCE LOCATED OVER
THE CENTRAL CARIBBEAN SEA. THE GFDL AND HWRF MODELS...PLUS ALL OF
THE GLOBAL MODELS EXCEPT FOR THE GFS...DEVELOP THE CARIBBEAN
DISTURBANCE TO VARIOUS DEGREES OVER THE NEXT 5 DAYS...WHICH CAUSES
THE SUBTROPICAL RIDGE TO THE NORTH OF DARBY TO WEAKEN BY DAYS 3-4.
THIS RESULTS IN A WEAKENING OF THE STEERING FLOW...AND SOME OF THE
MODELS EVEN FORECAST SOME WEAK BINARY INTERACTION WITH THE
DEVELOPING CARIBBEAN DISTURBANCE AFTER THAT SYSTEM ENTERS THE
SOUTHERN GULF MEXICO. THE GFS DOES NOT SHOW ANY INTERACTION WITH
THE CARIBBEAN DISTURBANCE BECAUSE IT NEITHER DEVELOPS DARBY OR THE
OTHER SYSTEM. DUE TO THE POOR 06Z INITIALIZATION AND SHORT TERM
FORECAST TRENDS BY THE GFS MODEL...LESS WEIGHT HAS BEEN PLACED ON
THAT MODEL AND IT IS CONSIDERED AN OUTLIER. THE OFFICIAL FORECAST
MAINTAINS THE PREVIOUS FORECAST TREND OF SLOWING DOWN DARBY IN THE
72-120 HOUR TIME FRAME DUE TO EXPECTED INTERACTION WITH THE LARGE
CARIBBEAN SYSTEM...REGARDLESS OF WHETHER OR NOT THAT SYSTEM GOES ON
TO BECOME A TROPICAL CYCLONE.

THE RECENT SHARP INTENSIFICATION TREND WOULD SUGGEST THAT DARBY MAY
BE IN THE EARLY STAGES OF RAPID INTENSIFICATION. HOWEVER...DESPITE
THE IMPROVED BANDING FEATURES...CLOUD TOPS IN THE INNER CORE REGION
HAVE WARMED SUGGESTING THAT DRY AIR MAY BE ACTING TO ERODE THE
CENTRAL DEEP CONVECTION. THE GFS-BASED SHIPS MODEL INDICATES THAT
THE VERTICAL SHEAR WILL DECREASE TO LESS THAN 5 KNOTS OVER THE
COURSE OF THE NEXT 36 HOURS...WHICH WOULD STRONGLY FAVOR RAPID
INTENSIFICATION. THE OFFICIAL FORECAST TRACK IS A BLEND OF THE
SHIPS AND PREVIOUS FORECAST IN CASE THE EROSION OF THE INNER CORE
CONVECTION CONTINUES...AND ALSO TO MAINTAIN SOME CONTINUITY WITH
THE PREVIOUS ADVISORY. HOWEVER...THE SHIPS MODEL IS INDICATING A
GREATER THAN 40 PERCENT CHANCE OF RAPID INTENSIFICATION
OCCURRING...AND THIS SCENARIO WILL BE CLOSELY ASSESSED FOR THE NEXT
ADVISORY PACKAGE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 23/1500Z 11.8N 94.8W 45 KT
12HR VT 24/0000Z 12.2N 95.9W 50 KT
24HR VT 24/1200Z 12.6N 97.4W 60 KT
36HR VT 25/0000Z 12.9N 98.8W 65 KT
48HR VT 25/1200Z 13.2N 99.8W 70 KT
72HR VT 26/1200Z 13.7N 101.1W 70 KT
96HR VT 27/1200Z 14.2N 101.5W 70 KT
120HR VT 28/1200Z 14.7N 101.5W 65 KT

$$
FORECASTER STEWART

[HURAKAN]

Latest

[HURAKAN]

As I pointed out on page 1, the last time we had four named storms by the end of June was 1991. Well, we have TS Darby.

EP, 05, 2010062306, , BEST, 0, 114N, 936W, 35, 1005, TS, 34, NEQ, 0, 0, 45, 45, 1010, 180, 45, 45, 0, E, 0, , 0, 0, FIVE, M,

Code: Select all

Total storms: 14
Hurricanes: 10
Major hurricanes (Cat. 3+): 5


What is interesting too about their 1991 season, is that at the end it was below normal in the number of named storms. An early start doesn't mean you will finish ahead!

[HURAKAN]

Darby also wants to see

[HURAKAN]

23/1745 UTC 12.0N 95.7W T3.5/3.5 DARBY -- East Pacific

55 knots

[HURAKAN]

Darby has no time to waste ... could be a hurricane by tonight

[HurricaneBelle]

The most notable Darby since this guy:

http://www.youtube.com/watch?v=K-Uz-dPANDY

[Aquawind]

Ahh so now they are forecasting a hurricane.. Darby is going to eat a good slice of the ACE pie.. Looks to be a serious flood threat to Mexico..

[HURAKAN]

18z

EP, 05, 2010062318, , BEST, 0, 119N, 956W, 55, 995, TS

[CrazyC83]

Looks like a hurricane to me right now...although I might want to hold it at 60 kt for now.

[bob rulz]

I wouldn't be surprised to see this at 70mph at 2pm - it almost looks like a hurricane, if it's not already. Darby has developed very rapidly and looks to still be organizing.

[HURAKAN]

TROPICAL STORM DARBY ADVISORY NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052010
200 PM PDT WED JUN 23 2010

...DARBY RAPIDLY STRENGTHENING SOUTH OF THE GULF OF TEHUANTEPEC...


SUMMARY OF 200 PM PDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...12.0N 96.1W
ABOUT 295 MI...475 KM SSW OF SALINA CRUZ MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/HR
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 12 MPH...19 KM/HR
MINIMUM CENTRAL PRESSURE...995 MB...29.38 INCHES


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


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 200 PM PDT...2100 UTC...THE CENTER OF TROPICAL STORM DARBY WAS
LOCATED NEAR LATITUDE 12.0 NORTH...LONGITUDE 96.1 WEST. DARBY IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 12 MPH...19 KM/HR...AND THIS
GENERAL MOTION SHOULD CONTINUE FOR THE NEXT 48 HOURS. ON THE
FORECAST TRACK...DARBY IS EXPECTED TO REMAIN WELL SOUTH OF THE
MEXICAN COAST OVER THE NEXT TWO DAYS.

MAXIMUM SUSTAINED WINDS ARE NEAR 65 MPH...100 KM/HR...WITH HIGHER
GUSTS. ADDITIONAL STRENGTHENING IS FORECAST DURING THE NEXT 48
HOURS...AND DARBY COULD BECOME A HURRICANE ON THURSDAY.

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

ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB...29.38 INCHES.


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


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...800 PM PDT.

$$
FORECASTER STEWART

[HURAKAN]

TROPICAL STORM DARBY DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP052010
200 PM PDT WED JUN 23 2010

CONVECTIVE BANDING HAS CONTINUED TO INCREASE MARKEDLY AND A BANDING
EYE HAS OCCASIONALLY BEEN EVIDENT IN BOTH VISIBLE AND MICROWAVE
IMAGERY. UPPER-LEVEL OUTFLOW HAS ALSO BEEN IMPROVING...ESPECIALLY
IN THE WESTERN SEMICIRCLE. THE INITIAL INTENSITY IS INCREASED TO
55 KT BASED ON AN INTENSITY ESTIMATE OF T3.5/55 KT FROM SAB.

THE INITIAL MOTION ESTIMATE IS 285/10. THERE IS NO CHANGE TO THE
PREVIOUS FORECAST REASONING. THE FUTURE TRACK OF DARBY CONTINUES TO
WEIGH HEAVILY UPON THE DEVELOPMENT OF A DISTURBANCE LOCATED OVER
THE WEST-CENTRAL CARIBBEAN SEA. THE MAJORITY OF THE MODELS...
ESPECIALLY THE ECMWF...CONTINUE TO DEVELOP THE CARIBBEAN SEA
DISTURBANCE TO VARIOUS DEGREES OVER THE NEXT 5 DAYS AND MOVE THAT
SYSTEM INTO THE SOUTHERN GULF OF MEXICO. THIS RESULTS IN WEAKENING
OF THE SUBTROPICAL RIDGE TO THE NORTH OF DARBY BY 96-120 HOURS AND
CAUSES A DECREASE IN THE STEERING FLOW. BOTH THE GFS AND
GFS-PARALLEL RUNS TAKE A RATHER ANEMIC LOOKING DARBY QUICKLY
WESTWARD...WHICH ONCE AGAIN APPEARS TO BE DUE TO POOR MODEL
INITIALIZATION. AS A RESULT...LESS WEIGHT HAS BEEN PLACED ON THOSE
MODELS...WITH MORE WEIGHT BEING PLACED ON THE ECMWF...NOGAPS...
UKMET...AND CANADIAN MODELS.

DARBY APPEARS TO ALREADY BE ABOUT 12 HOURS INTO A RAPID
INTENSIFICATION PHASE. THIS TREND IS FORECAST TO CONTINUE FOR
ANOTHER 12 HOURS OR SO WITH SLOWER DEVELOPMENT AFTER THAT. A
23/1606Z TRMM OVERPASS INDICATED THAT THE EARLIER OBSERVED SLIGHT
WESTWARD TILT OF THE INNER CORE VORTEX COLUMN HAD DIMINISHED...
WHICH WOULD INDICATE THAT DARBY HAS BETTER VERTICAL STRUCTURE THAT
IS CONDUCIVE FOR CONTINUED STRENGTHENING. THE SHIPS MODEL SHOWS
LESS THAN 5 KT OF VERTICAL SHEAR THROUGH 48 HOURS...WHICH WOULD
ALSO SUPPORT CONTINUED STRENGTHENING...AND IT IS QUITE POSSIBLE
THAT DARBY COULD BE A MAJOR HURRICANE BY THAT TIME. BY 96 HOURS...
THE VERTICAL SHEAR IS EXPECTED TO INCREASE...BUT MUCH LESS NOW THAN
PREVIOUS EXPECTED. THE OFFICIAL INTENSITY FORECAST IS HIGHER THAN
THE PREVIOUS ADVISORY AND IS BASED ON A BLEND OF THE SHIPS AND LGEM
INTENSITY MODELS.


FORECAST POSITIONS AND MAX WINDS

INITIAL 23/2100Z 12.0N 96.1W 55 KT
12HR VT 24/0600Z 12.3N 97.2W 70 KT
24HR VT 24/1800Z 12.7N 98.8W 80 KT
36HR VT 25/0600Z 13.0N 100.0W 85 KT
48HR VT 25/1800Z 13.4N 101.0W 90 KT
72HR VT 26/1800Z 14.0N 102.0W 90 KT
96HR VT 27/1800Z 14.5N 102.1W 90 KT
120HR VT 28/1800Z 15.0N 102.1W 75 KT

$$
FORECASTER STEWART

[HURAKAN]

Code: Select all

Prob of RI for 25 kt RI threshold=    73% is   6.2 times the sample mean(11.8%)
 Prob of RI for 30 kt RI threshold=    51% is   6.3 times the sample mean( 8.1%)
 Prob of RI for 35 kt RI threshold=    45% is   7.9 times the sample mean( 5.7%)
 Prob of RI for 40 kt RI threshold=    28% is   6.9 times the sample mean( 4.1%)


Impressive

[KWT]

Looks like an impressive system...at this rate those calls for a weak EPAC season will bust quite badly, along with those super high Atl season...