Prognostic Meteorological Discussion
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FXCA20 KWBC 171920
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
219 PM EST TUE JAN 17 2017

TROPICAL DISCUSSION FROM JAN 17/12 UTC: AT UPPER LEVELS...A LONG
WAVE RIDGE EXTENDS NORTH ALONG 90W FROM THE EASTERN TROPICAL
PACIFIC TO THE CENTRAL USA. A LOW OVER WESTERN CHIHUAHUA IN
NORTHWEST MEXICO EXTENDS A TROUGH SOUTH ACROSS THE BAJA PENINSULA
TO THE EASTERN TROPICAL PACIFIC. THE LOW IS FORECAST TO LIFT TO
THE NORTHEAST ACROSS SOUTHERN NEW MEXICO TO WEST TEXAS LATER ON
WEDNESDAY. AS THE LOW LIFTS THE TROUGH WILL BEGIN TO PULL.
MEANWHILE...THE TROUGH WILL ENHANCE UPPER LEVEL MOISTURE TRANSPORT
ACROSS THE NORTHERN STATES OF MEXICO INTO THE USA. BEST MOISTURE
CONVERGENCE WITH THIS FEATURE IS EXPECTED BETWEEN COLIMA/NAYARIT
IN SOUTHWEST MEXICO AND SOUTHERN SINALOA. IN THIS AREA EXPECTING
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM THROUGH
WEDNESDAY MORNING. OTHER CONVECTION TOT HE NORTH IS TO AFFECT
PORTIONS OF SONORA-CHIHUAHUA AS WANING FRONT MOVES ALONG THE
NORTHERN BORDER...TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND
MAXIMA OF 10MM. A DEEPER/STRONG MID/UPPER LEVEL TROUGH
FOLLOWS...MOVING ACROSS SOUTHERN CALIFORNIA/ NORTHERN BAJA
PENINSULA LATER ON THURSDAY. THIS IS TO TRIGGER SCATTERED
CONVECTION WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM.
ON FRIDAY THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-35MM
WHILE SPREADING EAST ACROSS SONORA TO WESTERN CHIHUAHUA.

UNDER INFLUENCE OF THE AFOREMENTIONED MID LEVEL
PERTURBATIONS...THE MID/UPPER LEVEL RIDGE WILL GRADUALLY RELOCATE
TO THE WESTERN CARIBBEAN-EASTERN USA/WESTERN ATLANTIC EARLY ON
WEDNESDAY MORNING. IT IS TO THEN HOLD THROUGH THURSDAY
EVENING/FRIDAY MORNING. THE RIDGE IS TO FAVOR A TRADE WINDS CAP
ACROSS THE BAHAMAS-CUBA-HISPANIOLA. THIS IS TO BUILD ACROSS
CENTRAL AMERICA THROUGH WEDNESDAY EVENING/THURSDAY MORNING. AT LOW
LEVELS...BROAD RIDGE DOMINATES THE FLOW ACROSS THE WESTERN
ATLANTIC. THIS FAVORS A TIGHT GRADIENT ACROSS THE BASIN...WITH
NORTHEASTERLY TRADES OF 15-20KT ACROSS THE GREATER ANTILLES/ISLAND
CHAIN INTO THE CENTRAL CARIBBEAN. POLAR TROUGH EXITING THE EASTERN
USA ON WEDNESDAY WILL PRESS AGAINST THIS AXIS...LEADING TO RAPID
EROSION OF THE LOW LEVEL RIDGE. AS THE GRADIENT SLACKENS THE
TRADES WILL VEER TO THE EAST WHILE DECREASING TO 10-15KT. AS THE
TRADES WEAKEN...EXPECTING A DECREASE IN GENERATION OF TRADE WIND
SHOWERS ACROSS THE BASIN LATER ON WEDNESDAY-FRIDAY.
MEANWHILE...ACROSS THE NORTHERN AND EASTERN CARIBBEAN ISLES
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM IN
PASSING SHOWERS. FAIR WEATHER CONDITIONS TO THEN PREVAIL THROUGH
THE END OF THE WEEK. OVER THE ABC ISLES-NORTHERN VENEZUELA EXPECT
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM THROUGH
FRIDAY. EASTERLY TRADES ARE TO ALSO CONVERGE ACROSS EASTERN
NICARAGUA...WHERE WE EXPECT RAINFALL AMOUNTS OF 05-10MM/DAY AND
MAXIMA OF 15MM THROUGH WEDNESDAY MORNING. THEREAFTER...EXPECTING
RAINFALL AMOUNTS OF 00-05MM/DAY AND WIDELY ISOLATED MAXIMA OF
10MM. OVER BELIZE-YUCATAN...PASSING CLOUD CLUSTERS WILL FAVOR
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM...WITH MOST
ACTIVE TODAY AND ON THURSDAY.

EAST OF THE MID/UPPER LEVEL RIDGE...A TROUGH EXTENDS TO THE
SOUTHWEST ACROSS THE EASTERN CARIBBEAN TO COLOMBIA/WESTERN
VENEZUELA. THE RIDGE TO THE WEST IS TO INDUCE THE SOUTHWESTWARD
AMPLIFICATION OF THE MID LEVEL TROUGH ACROSS COLOMBIA TO THE
EASTERN PACIFIC EARLY ON WEDNESDAY. AXIS IS TO THEN SPLIT IN
TWO...WITH NORTHERN HALF TO GRADUALLY PULL ACROSS THE ISLAND CHAIN
TO THE CENTRAL ATLANTIC...WHILE THE SOUTHERN HALF EVOLVES INTO A
CLOSED LOW JUST WEST OF ECUADOR. THE LATTER IS TO THEN MEANDER
WEST INTO THE EASTERN TROPICAL PACIFIC. THE TROUGH ALOFT IS TO
VENT CONVECTION ACROSS THE GUIANAS THROUGH WEDNESDAY...TO FAVOR
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. ON
WEDNESDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM...WHILE
ON THURSDAY THE MAXIMA IS TO PEAK AROUND 15-30MM. ACROSS SOUTHERN
VENEZUELA AND COLOMBIA IT IS TO FAVOR RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-30MM. OVER COLOMBIA...MOST ACTIVE IS
EXPECTED OVER THE CAUCA VALLEY TO THE SOUTHWEST...WHERE ITCZ
RELATED CONVERGENCE IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 15-20MM. A SLIGHT INCREASE IS EXPECTED ON THURSDAY
WITH MAXIMA OF 15-25MM.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:

INITIAL   24     36     48     60     72     84     96    TYPE
NONE

JIMENEZ...IMN (COSTA RICA)
MIRANDA...INAMEH (VENEZUELA)
DAVISON...WPC (USA)

$$





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