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Tropical Discussion
 
(Latest Discussion - Issued 1851Z Jan 21, 2021)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EST THU JAN 21 2021

TROPICAL DISCUSSION FROM JANUARY 21/19 UTC: MID LEVEL HIGH OVER
THE WESTERN CARIBBEAN ANCHORS A BROAD RIDGE OVER THE BASIN...WITH
AXIS EXPECTED TO PERSIST THROUGH THE MEDIUM RANGE PERIOD. AS A
RESULT OF THE PERSISTENT MID/UPPER LEVEL RIDGE...POLAR
PERTURBATIONS STREAMING ACROSS NORTH AMERICA INTO THE WESTERN
ATLANTIC ARE EXPECTED TO BOTTOM OUT FAR TO THE NORTH.
FURTHERMORE...UNDER THE INFLUENCE OF THE PERSISTENT MID LEVEL
RIDGE...A FAIRLY STRONG TRADE WINDS INVERSION IS TO SETTLE ACROSS
THE SOUTHERN STATES OF MEXICO...THE BAHAMAS...CUBA...JAMAICA AND
HISPANIOLA. OVER THE NEXT FEW DAYS THIS IS TO CONTINUE INHIBITING
ORGANIZED DEEP CONVECTION. IN TRADE WIND EASTERLY
CONVERGENCE...HOWEVER...SHALLOW CONVECTION IS TO BUILD ACROSS
BELIZE/CENTRAL GUATEMALA-EASTERN NICARAGUA AND JAMAICA...TO
SUSTAIN LIGHT RAINFALL AMOUNTS WITH ACCUMULATION OF 00-05MM/DAY
AND MAXIMA OF 10MM.

ALTHOUGH THE RIDGE ALOFT IS TO BLOCK POLAR SYSTEMS FROM ENTERING
THE CARIBBEAN BASIN...PERTURBATIONS ON THE SOUTHERN STREAM ARE TO
LIFT ACROSS THE BAJA PENINSULA INTO NORTHWEST MEXICO/SOUTHWEST USA
FROM TIME-TO-TIME...WITH ONE EARLY THIS CYCLE TO SUSTAIN A WANING
FRONT ACROSS SONORA-SOUTHERN BAJA PENINSULA LATER TODAY. UNDER THE
INFLUENCE OF THIS FEATURE EXPECTING MODERATE RAINFALL AMOUNTS
ALONG THE SIERRA MADRE BETWEEN SONORA-SINALOA IN NORTHWEST MEXICO
TO TRIGGER ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-25MM EARLY
IN THE CYCLE. LESSER AMOUNTS ARE EXPECTED OVER SOUTHERN
BAJA...WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM.

ANOTHER MID/UPPER LEVEL TROUGH IS TO THEN LIFT ACROSS NORTHWEST
MEXICO ON SATURDAY...WITH THE ASSOCIATED FRONT SURGING ACROSS
CALIFORNIA TO NORTHERN BAJA PENINSULA LATER IN THE DAY. THIS IS TO
ALSO FAVOR MODERATE RAINFALL AMOUNTS WITH ACCUMULATION OF
05-10MM/DAY AND MAXIMA OF 15-20MM EXPECTED THROUGH SUNDAY MORNING.

FARTHER EAST...LACKING UPPER LEVEL SUPPORT...A SHALLOW FRONT IS
EXPECTED TO MEANDER SOUTH TO THE SOUTHEAST BAHAMAS/TURKS AND
CAICOS-CUBA TO THE NORTHWEST CARIBBEAN LATER TODAY...WITH AXIS TO
FAVOR A PREFRONTAL SHEAR LINE ACROSS PUERTO RICO/THE DOMINICAN
REPUBLIC. THROUGH FRIDAY AFTERNOON THE FRONT IS TO FRONTOLIZE AND
THE SHEAR LINE IS TO BECOME ILL DEFINED. MEANWHILE...THIS WILL
ENHANCE LOW LEVEL MOISTURE CONVERGENCE TO TRIGGER LIGHT RAINFALL
AMOUNTS...WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM.

ALTHOUGH THE ENVIRONMENTAL CONDITIONS OVER THE NORTHERN CARIBBEAN
ARE QUITE HOSTILE TO DEVELOPMENT...CONDITIONS TO THE SOUTH ARE
SOMEWHAT MORE FAVORABLE TO DEVELOPMENT. THIS IS PARTICULARLY TRUE
ACROSS SOUTHERN NICARAGUA-COATS RICA TO WESTERN PANAMA...WHERE
MODERATE CONVECTION EARLY IN THE CYCLE IS TO SUSTAIN ACCUMULATION
OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ON FRIDAY THIS DECREASES TO
00-05MM/DAY AND MAXIMA OF 10MM...WHILE ON SATURDAY IT INCREASES TO
05-10MM/DAY AND MAXIMA OF 15MM. DEEPER CONVECTION IS EXPECTED ON
THE ANDEAN REGION/WESTERN COLOMBIA...WITH ACCUMULATION OF
10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH
SATURDAY...HOWEVER...THIS WEAKENS TO 05-10MM/DAY AND MAXIMA OF
15-20MM. OVER SOUTHERN AMAZONIA IN SOUTHERN COLOMBIA TO EASTERN
ECUADOR AN MCS IS TO FORM LATER IN THE WEEK...WITH CONVECTION
INCREASING FROM 15-20MM/DAY AND MAXIMA OF 25-50MM EARLY IN THE
CYCLE TO 20-40MM/DAY AND MAXIMA OF 75-150MM ON FRIDAY-SATURDAY.
ACROSS THE GUIANAS...MOST INTENSE IS EXPECTED EARLY IN THE
CYCLE...WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON
FRIDAY-SATURDAY THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF
20-35MM.

TROPICAL WAVES/TUTT INDUCED PERTURBATIONS/TRADE WIND SURGES
NONE

DAVISON...WPC (USA)