WTNT44 KNHC 111439
TCDAT4
 
TROPICAL DEPRESSION FOURTEEN DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
1100 AM AST TUE SEP 11 2012
 
ALTHOUGH THERE IS NOT MUCH DEEP CONVECTION NEAR THE CENTER OF
CIRCULATION OF THE LOW PRESSURE SYSTEM OVER THE CENTRAL TROPICAL
ATLANTIC...AN OUTER CONVECTIVE BAND TO THE WEST OF THE CENTER HAS
CONTINUED TO BECOME BETTER ORGANIZED.  DVORAK ESTIMATES HAVE RISEN
TO T2.5 FROM TAFB AND T2.0 FROM SAB...SUPPORTING THE DESIGNATION OF
THIS SYSTEM AS A TROPICAL DEPRESSION.

THE INITIAL MOTION IS ESTIMATED TO BE WESTWARD...OR 275/9 KT.  THE
DEPRESSION SHOULD BE TURNING WEST-NORTHWESTWARD VERY SOON AS IT
MOVES ALONG THE SOUTHWESTERN EDGE OF THE SUBTROPICAL RIDGE...WHICH
CURRENTLY EXTENDS FROM AFRICA WESTWARD TO 50W.  THE RIDGE IS
EXPECTED TO WEAKEN OVER THE NEXT 5 DAYS WHILE BEING ERODED BY A
LARGE MID-/UPPER-LEVEL LOW THAT WILL BE DROPPING SOUTH OF THE
AZORES...AND THE DEPRESSION SHOULD RESPOND BY TURNING NORTHWARD BY
DAY 4 AND NORTHEASTWARD BY DAY 5.  THE TRACK GUIDANCE IS IN GOOD
AGREEMENT UNTIL ABOUT 72 HOURS WHEN THE ECMWF MODEL BEGINS TO LAG
BEHIND THE OTHER MODELS...BUT THIS IS COMPENSATED FOR IN THE MODEL
CONSENSUS BY THE FASTER GFDL AND HWRF MODELS.  THE OFFICIAL NHC
FORECAST INDICATES A TRACK LEANING TOWARDS THE SLOWER SCENARIO...
AND IS VERY CLOSE TO THE GFS SOLUTION.

SATELLITE IMAGERY INDICATES THAT THE DEPRESSION IS BORDERED BY DRY
SAHARAN AIR TO ITS NORTH AND WEST...BUT THE CYCLONE IS ALSO DRAWING
IN MOIST AIR FROM THE SOUTH.  SINCE DEEP CONVECTION NEAR THE
CENTER IS SCANT...IT MIGHT TAKE SOME TIME FOR THE DEPRESSION TO
STRENGTHEN UNTIL IT CAN MIX OUT SOME OF THE DRY AIR.  SHEAR IS
EXPECTED TO BE LOW FOR THE NEXT 3 DAYS OR SO...AND STRENGTHENING IS
INDICATED IN THE OFFICIAL FORECAST UP TO THAT TIME.  STRENGTHENING
COULD BE ARRESTED IN 4-5 DAYS WHEN THE CYCLONE BEGINS TO ENCOUNTER
WESTERLY SHEAR.  THERE IS SOME SIGNIFICANT SPREAD IN THE INTENSITY
MODELS AT THE LATTER END OF THE FORECAST PERIOD...WITH THE SHIPS
AND LGEM MODELS BEING 20-25 KT DIFFERENT FROM EACH OTHER.  SINCE
THE LGEM MODEL...WHICH IS THE LOWER OF THE TWO...IS DESIGNED TO
BETTER HANDLE CHANGES IN THE SHEAR AT THE LONGER FORECAST TIMES...
IT IS POSSIBLE THAT THE CYCLONE COULD BE WEAKER THAN INDICATED IN
THE FORECAST ON DAYS 4 AND 5.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/1500Z 16.3N  43.1W   30 KT  35 MPH
 12H  12/0000Z 17.0N  44.5W   35 KT  40 MPH
 24H  12/1200Z 18.3N  46.8W   40 KT  45 MPH
 36H  13/0000Z 19.8N  49.3W   50 KT  60 MPH
 48H  13/1200Z 21.4N  51.3W   60 KT  70 MPH
 72H  14/1200Z 25.0N  54.0W   65 KT  75 MPH
 96H  15/1200Z 28.5N  53.5W   65 KT  75 MPH
120H  16/1200Z 30.5N  51.0W   65 KT  75 MPH
 
$$
FORECASTER BERG
 

WTNT44 KNHC 112034
TCDAT4
 
TROPICAL DEPRESSION FOURTEEN DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
500 PM AST TUE SEP 11 2012
 
SOME DEEP CONVECTION HAS DEVELOPED CLOSER TO THE CENTER OF TD
FOURTEEN...AND CLOUDINESS HAS INCREASED WITHIN THE CIRCULATION. 
HOWEVER...THE ORGANIZATION OF THE CONVECTION HAS NOT CHANGED MUCH
FROM THIS MORNING...AND DVORAK FINAL-T NUMBERS REMAIN T2.5 FROM
TAFB AND T2.0 FROM SAB.  SINCE THERE IS NOT YET CONSENSUS FROM BOTH
AGENCIES...THE INTENSITY IS BEING HELD AT 30 KT.

THE DEVELOPMENT OF CONVECTION NEAR THE CENTER MAY BE AN INDICATION
THAT THE DEPRESSION WILL BE STRENGTHENING SOON.  THE CYCLONE SHOULD
HAVE GOOD UPPER-LEVEL OUTFLOW FOR THE NEXT 3 DAYS OR SO DUE TO LIGHT 
VERTICAL SHEAR...AND THE NHC FORECAST CONTINUES TO SHOW THE SYSTEM
STRENGTHENING TO A HURRICANE IN THAT TIME SPAN.  THE MID-LATITUDE
WESTERLIES ARE THEN EXPECTED TO STRENGTHEN SIGNIFICANTLY OVER THE
ATLANTIC BY DAY 4.  CONSEQUENTLY...THE CYCLONE WILL BE AFFECTED BY
20-25 KT OF WESTERLY SHEAR AT THE LATTER END OF THE FORECAST
PERIOD.  IN FACT...THE LGEM MODEL CONTINUES TO SHOW THE LEAST
AMOUNT OF STRENGTHENING OF ALL THE INTENSITY MODELS AND BARELY
BRINGS THE CYCLONE TO 50 KT.  THE ONLY CHANGE TO THE PREVIOUS
INTENSITY FORECAST IS TO SHOW SOME WEAKENING ON DAY 5 DUE TO THE
EXPECTED SHEAR.

THE DEPRESSION HAS TURNED MORE QUICKLY THAN PREVIOUSLY
ANTICIPATED...AND IT NOW HAS AN ESTIMATED MOTION OF 305/10 KT. 
THERE HAS BEEN NO CHANGE TO THE FORECAST TRACK REASONING...WITH THE
DEPRESSION EXPECTED TO TURN NORTHWARD AND THEN NORTHEASTWARD AS THE
SUBTROPICAL RIDGE WEAKENS.  THE ONE NOTEWORTHY POINT IS THAT THE
NEW ECMWF RUN CONTINUES TO DIVERGE FROM THE OTHER TRACK MODELS...
THIS TIME SHOWING A STRONGER EASTWARD MOTION AND A SHARPER
RECURVATURE.  THE NEW NHC FORECAST STILL LIES TO THE EAST OF THE
MODEL CONSENSUS TVCA TO ACCOUNT FOR THE ECMWF SOLUTION.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/2100Z 17.5N  43.8W   30 KT  35 MPH
 12H  12/0600Z 18.5N  45.4W   35 KT  40 MPH
 24H  12/1800Z 19.9N  47.8W   40 KT  45 MPH
 36H  13/0600Z 21.4N  50.1W   50 KT  60 MPH
 48H  13/1800Z 23.2N  52.0W   60 KT  70 MPH
 72H  14/1800Z 27.0N  54.0W   65 KT  75 MPH
 96H  15/1800Z 30.0N  52.5W   65 KT  75 MPH
120H  16/1800Z 31.5N  49.5W   60 KT  70 MPH
 
$$
FORECASTER BERG
 

