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The Weather Prediction Center
 
Tropical Discussion
 
(Latest Discussion - Issued 1833Z Sep 19, 2017)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT TUE SEP 19 2017

AT 15 UTC HURRICANE MARIA CENTERED NEAR 16.3N 63.1W..WITH MAXIMUM
SUSTAINED WINDS OF 140KT AND CENTRAL PRESSURE OF 927 HPA. THE
HURRICANE IS MOVING TO THE WEST-NORTHWEST AT 09KT.

AT 15 UTC TROPICAL DEPRESSION NORMA CENTERED NEAR 21.6N
114.5W...WITH MAXIMUM SUSTAINED WINDS OF 30KT AND CENTRAL PRESSURE
OF 1006 HPA. THE DEPRESSION IS MOVING WEST AT 04KT. SEE NHC
BULLETIN FOR DETAILS.

TROPICAL DISCUSSION FROM SEP 19/12 UTC: CONSISTENT WITH PREVIOUS
ANALYSIS AND FORECAST A MID/UPPER LEVEL RIDGE EXTENDS WEST-TO-EAST
ACROSS MEXICO TO THE GULF ALONG 22N/23N. THE RIDGE ALOFT IS
VENTING DIURNAL CONVECTION ALONG THE SIERRA MADRE BETWEEN
SONORA-SINALOA IN WESTERN MEXICO AND ACROSS THE SOUTHWEST STATES
OF COLIMA-NAYARIT-JALISCO. IN THIS AREA EXPECTING RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH WEDNESDAY IT
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-25MM...WITH LESSER
AMOUNTS OVER SONORA/SINALOA. OVER SOUTHERN MEXICO INITIALLY
EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM.
ON WEDNESDAY MOST ACTIVE IS EXPECTED ALONG THE COAST BETWEEN
GUERRERO AND SOUTHERN OAXACA...WITH MAXIMA OF 20-30MM. OTHER
CONVECTION IS TO CLUSTER OVER THE YUCATAN PENINSULA TO NORTHERN
GUATEMALA/BELIZE...WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA
OF 15-20MM. ON WEDNESDAY THE DAILY MAXIMA DECREASES TO
15MM...WHILE ON THURSDAY EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY
AND MAXIMA OF 10MM.

DOWNSTREAM FROM THE CONTINENTAL RIDGE...AN ELONGATED TROUGH
EXTENDS FROM THE FAR WESTERN ATLANTIC TO CUBA/NORTHWEST CARIBBEAN.
THIS GRADUALLY WEAKENS TO A SHORT WAVE TROUGH OVER THE WESTERN
CARIBBEAN ON WEDNESDAY-THURSDAY. MEANWHILE...THIS WILL VENT
DIURNAL CONVECTION ACROSS NORTHERN HONDURAS-NORTHEAST
NICARAGUA...TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF
15-20MM. HIGHER AMOUNTS ARE EXPECTED TO THE SOUTH...WHERE IN
INTERACTION WITH THE EASTERN PACIFIC ITCZ EXPECTING SCATTERED
CONVECTION TO AFFECT SOUTHERN GUATEMALA-EL SALVADOR AND ALONG THE
CONTINENTAL DIVIDE OVER WESTERN NICARAGUA. IN THIS AREA EXPECTING
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM.

A TUTT TO THE EAST ANCHORS ON A CLOSED LOW TO THE SOUTH OF HAITI.
UNDER THE INFLUENCE OF THE TROUGH TO THE WEST THE TUTT LOW WILL
LIFT ACROSS THE WINDWARD CHANNEL/EASTERN CUBA LATER TODAY...TO
QUICKLY PULL ACROSS THE BAHAMAS ON WEDNESDAY. AS IT LIFTS ACROSS
HAITI IT IS TO FAVOR SCATTERED CONVECTION WITH ACCUMULATION OF
05-10MMD/AY AND MAXIMA OF 15-25MM...WHILE ACROSS THE DOMINICAN
REPUBLIC EXPECTING RAINFALL AMOUNTS OF 15-20MM AND MAXIMA OF
35-70MM. OVER JAMAICA AND THE CAYMAN ISLES THIS IS TO FAVOR
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. AS IT PULLS
ACROSS THE BAHAMAS ON WEDNESDAY THIS IS TO FAVOR RAINFALL AMOUNT
OF 05-10MM/DAY AND MAXIMA OF 15MM.

ALSO OVER THE WESTERN ATLANTIC...AT 500/250 HPA...A CELL OF THE
SUBTROPICAL RIDGE DOMINATES THE FLOW NORTH OF THE GREATER ANTILLES
WHILE CENTERING ON A CLOSED HIGH NEAR 27N 62W. THE RIDGE IS
STEERING HURRICANE MARIA ACROSS THE EASTERN CARIBBEAN. PER NHC
GUIDANCE THE HURRICANE REACHES SOUTHEAST PUERTO RICO ON WEDNESDAY
MORNING...EXITING OVER NORTHWEST PUERTO RICO LATER IN THE DAY. IT
IS THEN EXPECTED TO TRACK NORTH OF THE DOMINICAN REPUBLIC AND TO
THE EAST OF THE TURKS AND CAICOS. AS THE HURRICANE MODULATES THE
ITCZ ACROSS THE WINDWARD ISLES THIS WILL RESULT IN RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 35-70MM DURING THE NEXT
COUPLE OF DAYS. ACROSS THE LEEWARD ISLANDS INITIALLY EXPECTING
ADDITIONAL RAINFALL AMOUNTS OF 20-30MM/DAY AND MAXIMA OF 75-125MM.
ON WEDNESDAY THIS DECREASES TO 15-20MM/DAY AND MAXIMA OF
35-70MM...AND THROUGH THURSDAY THE MAXIMA IS TO PEAK AT 25-50MM.
OVER THE NORTHERN VIRGIN ISLES THIS WILL TRIGGER RAINFALL AMOUNTS
OF 100-200MM/DAY AND MAXIMA OF 300MM...WHILE ACROSS PUERTO RICO
EXPECTING RAINFALL AMOUNTS OF 250-375MM AND MAXIMA OF 500-625MM.
MOST INTENSE OVER PUERTO RICO IS EXPECTED ACROSS EASTERN PORTIONS
OF THE ISLAND. FEEDER BAND CONVERGENCE ON THURSDAY WILL THEN
RESULT IN ADDITIONAL RAINFALL AMOUNTS OF 25-50MM/DAY AND MAXIMA OF
75-150MM. OVER THE DOMINICAN REPUBLIC THIS IS TO TRIGGER RAINFALL
AMOUNTS OF 25-50MM/DAY AND MAXIMA OF 75-125MM ON
WEDNESDAY-THURSDAY. ON THURSDAY TO FRIDAY THIS INCREASES TO
100-200MM/DAY AND MAXIMA OF 300MM. OVER NORTHERN HAITI EXPECTING
RAINFALL AMOUNTS OF 100-200MM/DAY AND MAXIMA OF 300MM ON
THURSDAY...WHILE ACROSS THE HAITIAN PENINSULA EXPECTING RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. OVER THE
TURKS/SOUTHEAST BAHAMAS IT IS TO TRIGGER RAINFALL AMOUNTS OF
75-150MM/DAY AND MAXIMA OF 250MM.

OVER WESTERN COLOMBIA/ANDEAN REGION INITIALLY EXPECTING RAINFALL
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON WEDNESDAY THIS
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER NORTHERN
COLOMBIA AND ACROSS VENEZUELA TO GUYANA EXPECTING RAINFALL AMOUNTS
OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THIS IS TO HOLD THROUGH
MIDMORNING ON WEDNESDAY...WHEN ACTIVITY STARTS TO WANE FROM THE
EAST. DURING THAT PERIOD CONVECTION ACROSS GUYANA-EASTERN
VENEZUELA DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-20MM. THROUGH
THURSDAY THIS EXPANDS ACROSS VENEZUELA TO EASTERN COLOMBIA.

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:
INITIAL   24    36    48    60    72    84    96   TYPE  SOF
21W      25W   29W   33W   37W   41W   44W   48W   TW    18N
93W      95W   96W   97W   98W   99W  101W  103W   TW    21N

TROPICAL WAVE ALONG 21W AND SOUTH OF 18N IS TO CONFINE TO THE
ATLANTIC ITCZ.

TROPICAL WAVE ALONG 93W AND SOUTH OF 21N IS TO SLOWLY PROPAGATE
ALONG THE EASTERN PACIFIC ITCZ. NOTE THAT THE NHC IS MONITORING
THIS FEATURE FOR POSSIBILITY OF A TROPICAL CYCLONE FORMING LATER
THIS WEEK. ON THE SOUTHERN STATES OF MEXICO THIS WILL RESULT IN
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. ACROSS
SOUTHWEST MEXICO IT IS TO THEN TRIGGER RAINFALL AMOUNTS OF
10-15MM/DAY AND MAXIMA OF 20-30MM AND WEDNESDAY AND THURSDAY.
ACROSS VERACRUZ...MEANWHILE...EXPECTING RAINFALL AMOUNTS OF
05-10MM/DAY AND MAXIMA OF 15-20MM.

GUY...NMS (BELIZE)
RIVAS...SENAMHI (PERU)
DAVISON/GALVEZ...WPC (USA)