The HPC discussion:
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
153 PM EST WED JAN 16 2013
DISCUSSION FROM JAN 16/00UTC: LONG WAVE POLAR TROUGH OVER NORTH
AMERICA CONTINUES TO PRESS EAST INTO THE CENTRAL PLAINS...AND
THROUGH 42/48 HRS IT IS TO REACH THE EASTERN USA WHERE IT IS TO
THEN LIFT OVER A WANING RIDGE. ASSOCIATED SURFACE FRONT IS RACING
ACROSS THE GULF OF MEXICO...AND UNDER INFLUENCE OF A 30-35KT
NORTHERLY SURGE IT IS TO PUSH ACROSS THE FLORIDA PANHANDLE TO
CAMPECHE/TABASCO-OAXACA IN SOUTHERN MEXICO BY 24 HRS. THROUGH 36
HRS IT WILL MOVE ACROSS THE YUCATAN TO GUATEMALA...WITH A 50KT
TEHUANTEPECER JET ESTABLISHING OVER THE EASTERN PACIFIC. THROUGH
48-60 HRS THE FRONT MOVES INTO THE NORTHWEST BAHAMAS-WESTERN
CUBA-GULF OF HONDURAS/GUATEMALA. NORTHERLY WINDS OF 25-30KT ARE TO
ACCOMPANY THIS FRONT AS IT ENTERS THE WESTERN CARIBBEAN. BY 72 HRS
IT WILL MOVE TO CENTRAL BAHAMAS/CENTRAL CUBA WHILE TRAILING ACROSS
THE NORTHWEST CARIBBEAN. LATER IN THE CYCLE THE FRONT WILL START
TO RETROGRESS. FURTHERMORE...A SHORT LIVED PREFRONTAL SHEAR LINE
IS TO FORM AHEAD OF THIS BOUNDARY BY 54-78/84 HRS...TO EXTEND
ACROSS EASTERN CUBA-JAMAICA TO NICARAGUA.
AS THE FRONT SURGES ACROSS THE SOUTHERN STATES OF MEXICO EARLY
THIS CYCLE IT WILL SUSTAIN RAINFALL AMOUNTS 20-30MM/DAY AND MAXIMA
OF 75-150MM/DAY. BY 48-60 HRS THIS WILL DECREASE TO 15-20MM/DAY
AND MAXIMA OF 30-60MM. ACROSS GUATEMALA EXPECTING RAINFALL AMOUNTS
OF 15-30MM/DAY AND MAXIMA OF 40-80MM BY 18-42 HRS. OVER THE
NORTHWEST CARIBBEAN TO NORTHERN HONDURAS...EXPECTING RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM/DAY BY 24-48
HRS...AND 20-40MM/DAY AND MAXIMA OF 75-125MM/DAY BY 48-108 HRS.
DURING THAT PERIOD...LOCALIZED MAXIMA OF 150-200MM ARE HIGHLY
LIKELY DUE TO STRONG LOW LEVEL CONVERGENCE. OVER WESTERN-CENTRAL
CUBA THE FRONTAL CONVECTION WILL SUSTAIN RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-35MM/DAY...WHILE OVER NORTHWEST
BAHAMAS EXPECT ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15MM.
OVER THE CAYMAN ISLANDS EXPECTING ACCUMULATION OF 05-10MM/DAY AND
MAXIMA OF 15MM. THROUGH 72-84 HRS THE MAXIMA WILL INCREASE TO
20-30MM. SHEAR LINE CONVERGENCE ACROSS EASTERN CUBA WILL SUSTAIN
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM...WHILE ACROSS
EASTERN NICARAGUA EXPECT ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF
20-30MM.
MID/UPPER LEVEL RIDGE OVER THE WESTERN ATLANTIC/EASTERN USA IS
YIELDING TO PROGRESSIVE POLAR TROUGH STREAMING ACROSS NORTH
AMERICA. THROUGH 48-60 HRS THE MID LEVEL RIDGE IS TO REPOSITION TO
THE NORTH-NORTHEAST OF THE LEEWARD ISLANDS...AND BY 72-96 HRS IT
IS TO SETTLE OVER THE CENTRAL ATLANTIC. AS THE RIDGE PATTERN
RELOCATES...SUBSIDENCE/TRADE WIND CAP ACROSS SOUTHERN
MEXICO-NORTHERN CENTRAL AMERICA IS FORECAST TO WEAKEN. OVER THE
CENTRAL AND EASTERN CARIBBEAN...THE SUBSIDENCE CAP WILL BE
STRONGER AND MORE RESILIENT AND IN THIS AREA IT IS TO CONTINUE
INHIBITING DEEP CONVECTION. A TUTT BOUNDS THE SOUTHERN FRINGES OF
THE UPPER LEVEL RIDGE...WITH AXIS ACROSS THE GREATER ANTILLES TO A
CLOSED LOW OVER THE WESTERN CARIBBEAN. AS THE RIDGE MEANDERS
EAST...THE TROUGH WILL CUT OFF...THEN START TO WEAKEN/FILL AS IT
LIFTS NORTH ACROSS CUBA BY 48 HRS. ALTHOUGH IT TENDS TO
WEAKEN...COLD CORE FEATURE IS LIKELY TO ENHANCE VENTILATION ALOFT
WHILE FAVORING A CONVECTIVELY UNSTABLE AIR MASS. BEST INSTABILITY
IS EXPECTED ACROSS EASTERN NICARAGUA/WESTERN CARIBBEAN EARLY IN
THE CYCLE...AND CENTRAL/WESTERN CUBA BY 30-42 HRS. AS IT ENHANCES
INSTABILITY ACROSS CUBA-THE CAYMAN ISLES AND NORTHERN VENEZUELA
THIS WILL RESULT AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.
AT LOW LEVELS IT REFLECTS AS A BROAD RIDGE OVER THE WESTERN
ATLANTIC AND TO THE NORTH OF THE ISLANDS. THIS RIDGE IS TO ALSO
MOVE TO THE CENTRAL ATLANTIC BY 36-48HRS...AND FURTHER EAST LATER
IN THE CYCLE. AS IT PULLS AWAY...AND THE GRADIENT SLACKENS...
TRADES ACROSS THE EASTERN AND NORTHERN CARIBBEAN WILL DECREASE TO
10-15KT. WINDS ARE TO ALSO VEER TO THE EAST-NORTHEAST LATER
TODAY...AND TO THE EAST-SOUTHEAST DURING THE WEEKEND. ALTHOUGH
FLOW PATTERN CHANGES...MOIST ADVECTION WILL PERSIST ACROSS THE
EASTERN CARIBBEAN ISLANDS...WITH TRADE WIND SHOWERS TO PESTER THE
THESE ISLES. ACROSS THE ISLAND CHAIN-NORTHERN CARIBBEAN ISLES
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND WIDELY ISOLATED
MAXIMA OF 10MM. OVER EASTERN NICARAGUA/NORTHEAST HONDURAS
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-25MM/DAY.
EAST OF THE WESTERN ATLANTIC RIDGE...OVER THE CENTRAL-EASTERN
ATLANTIC...A TROUGH EXTENDS BETWEEN 50W-30W TO NORTHERN BRASIL-THE
GUIANAS. AS THE RIDGE RELOCATES INTO THE CENTRAL ATLANTIC...THE
TROUGH IS TO CUT OFF FROM THE MEAN FLOW...AND BY 42-48 HRS IT WILL
START TO FILL/WEAKEN. MEANWHILE...AS IT HOLDS OVER THE CENTRAL
ATLANTIC...IT IS TO INTERACT WITH THE ITCZ...PROVIDING THE
VENTILATION ALOFT THAT IS TO ENHANCE CONVECTIVE DEVELOPMENT ALONG
THE CONVERGENCE ZONE. THIS IS TO ALSO ENHANCE DIURNAL CONVECTION
ACROSS THE NORTHERN GUIANAS WHERE WE EXPECT RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM/DAY. THROUGH 48 HRS THIS WILL
DECREASE TO 05-10MM/DAY AND MAXIMA OF 15MM.
OVER THE EASTERN PACIFIC...THE ITCZ MEANDERS INLAND OVER COLOMBIA
BETWEEN THE EJE CAFETERO TO THE NORTH AND THE CAUCA VALLEY TO THE
SOUTH. IN THIS AREA EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND
MAXIMA OF 20-35MM/DAY. THROUGH 72-96 HRS THIS WILL DECREASE TO
05-10MM/DAY AND MAXIMA OF 15MM. OVER EJE CAFETERO TO THE
NORTH...EXPECT ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM.
ALVAREZ...ONAMET (REPUBLICA DOMINICANA)
GALDAMEZ...DGOA-MARN (EL SALVADOR)
DAVISON...HPC (USA)
