000
AXNT20 KNHC 211727
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST MON JAN 21 2013

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF 
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE 
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE 
IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL 
ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1645 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS THROUGH SOUTHERN LIBERIA INTO THE 
EASTERN TROPICAL ATLC ALONG 5N9W TO 2N17W. THE ITCZ BEGINS AT 
2N17W AND CONTINUES ALONG 4N26W 1N41W. ISOLATED MODERATE 
CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 
10W-37W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING IS ACROSS THE GULF OF MEXICO PROVIDING 
LIGHT ANTI-CYCLONIC FLOW ACROSS THE BASIN. SURFACE WIND SPEEDS 
RANGE FROM 5-15 KT. MULTI-LAYERED CLOUDS ARE KEEPING A GOOD 
PORTION OF THE AREA UNDER OVERCAST SKIES WITH POSSIBLE ISOLATED 
SHOWERS. ALOFT...THE UPPER LEVEL CLOUDS ARE THE RESULT OF 
MOISTURE BEING DRAWN FROM THE E PACIFIC ACROSS THE GULF AROUND 
AN UPPER LEVEL RIDGE ACROSS THE NW CARIBBEAN. LITTLE CHANGE IS 
EXPECTED OVER THE NEXT 24 HOURS. 

CARIBBEAN SEA...
DRY AIR ALOFT COVERS THE CARIBBEAN TODAY DESPITE THE PRESENCE OF 
AN UPPER LEVEL TROUGH EXTENDING FROM THE WINDWARD PASSAGE TO 
COSTA RICA WITH TWO UPPER RIDGES TO EITHER SIDE. THE DRY AIR IS 
HELPING MAINTAIN FAIR CONDITIONS AT THE SURFACE. A FEW POSSIBLE 
ISOLATED SHOWERS ARE ACROSS THE NW CARIBBEAN FROM JAMAICA TO 
HONDURAS. TRADEWIND FLOW OF 15-20 KT DOMINATES MUCH OF THE AREA 
WITH A SMALL PORTION OF 25 KT WINDS NEAR THE COAST OF COLOMBIA. 
LITTLE CHANGE IS EXPECTED OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
ZONAL WESTERLY FLOW ALOFT COVERS THE WEST ATLC EXCEPT FOR A WEAK 
SHORTWAVE TROUGH MOVING AROUND A BROADER UPPER TROUGH ACROSS THE 
NORTHERN CONUS. THE SHORTWAVE IS SUPPORTING A STATIONARY FRONT 
THAT EXTENDS FROM A WEAK 1016 MB LOW NEAR 32N70W TO 25N80W. 
POSSIBLE ISOLATED SHOWERS ARE WITHIN 100 NM SE OF THE AXIS. THE 
REMAINDER OF THE BASIN IS DOMINATED BY BROAD SURFACE RIDGING 
ANCHORED BY A 1031 MB HIGH NEAR 37N34W. THE SURFACE RIDGE IS 
SUPPORTED BY AN UPPER LEVEL RIDGE ACROSS THE CENTRAL ATLC ALONG 
31N48W...AND A SECOND UPPER RIDGE OVER WEST AFRICA ALONG 28N17W. 
A WEAK UPPER TROUGH IS SANDWICHED BETWEEN THE TWO UPPER RIDGES 
NEAR 30W. THE UPPER TROUGH IS CAUSING NO ACTIVE WEATHER IN THE 
DISCUSSION AREA. HOWEVER...IT IS SUPPORTING A FRONTAL BOUNDARY 
THAT EXTENDS THROUGH THE SURFACE RIDGE WITH AXIS JUST NORTH OF 
THE AREA NEAR 31N. THE FRONT WILL LIKELY DIP SOUTH INTO THE AREA 
SHORTLY.  

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON