[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 170550
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT JUL 17 2010

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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC...

...TROPICAL WAVES...

A WELL DEFINED TROPICAL WAVE EXTENDS FROM 19N43W TO 8N45W WITH
SOME CYCLONIC TURNING ALONG THE WAVE AXIS NEAR 16N. THE WAVE IS
MOVING W NEAR 20 KT AND REMAINS EMBEDDED WITHIN AN AREA OF DEEP
LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER
ANIMATION. AN ASCAT PASS FROM 2348 UTC INDICATED NE WINDS OF 20
KT NEAR THE NORTHERN END OF THE WAVE AXIS DUE TO THE PRES
GRADIENT BETWEEN THIS SYSTEM AND THE ATLC RIDGE EXTENDING ALONG
32N. SAHARAN AIR LAYER IN THE VICINITY OF THE WAVE IS
SUPPRESSING CONVECTION FROM DEVELOPING...LEAVING ONLY SCATTERED
SHOWERS AND ISOLATED TSTMS NEAR 12N46W. THIS WAVE WILL REACH 55W
THIS EVENING AND THE EASTERN CARIBBEAN SUN NIGHT BRINGING AN
INCREASE IN SHOWER AND TSTMS ACTIVITY PARTICULARLY TO THE
LEEWARD ISLANDS AND THEN OVER PUERTO RICO AND THE US/UK VIRGIN
ISLANDS BY MON.

TROPICAL WAVE IS MOVING ACROSS THE LESSER ANTILLES WITH AXIS
ALONG 61W FROM 8N TO 16N. THIS FEATURE IS MOVING W ABOUT 15 KT.
A DIFFLUENT PATTERN ALOFT BETWEEN AN UPPER-LEVEL LOW APPROACHING
PUERTO RICO AND A RIDGE OVER THE EASTERN CARIBBEAN IS HELPING TO
INDUCE CONVECTION NEAR THE WAVE AXIS. SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION IS SEEN FROM 14N TO 18N BETWEEN 60W
AND 63W.

TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 71W S OF 17N
MOVING W AT ABOUT 10 KT. SCATTERED MODERATE TO STRONG CONVECTION
CAN BE FOUND WITHIN AROUND 200 NM EITHER SIDE OF THE WAVE AXIS S
OF 13N TO THE COAST OF SOUTH AMERICA...INCLUDING INLAND PORTIONS
OF WESTERN VENEZUELA AND EASTERN COLOMBIA. THE WAVE IS ALSO
ENHANCING CONVECTION JUST S OF HISPANIOLA. THIS WAVE WILL MOVE
INTO THE W CARIBBEAN TODAY.

...ITCZ...

THE ITCZ AXIS IS ALONG 10N15W 7N30W 10N44W 9N50W 12N58W.
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF
THE AXIS E OF 33W TO THE WEST COAST OF AFRICA. SIMILAR
CONVECTION IS FROM 5N-8N BETWEEN 38W AND 45W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH CONTINUES TO MOVE WWD ACROSS THE CENTRAL GULF
WITH AXIS ALONG 91W...FROM THE COAST OF LOUISIANA TO THE YUCATAN
PENINSULA NEAR 19N90W. THERE ARE NO SIGNS OF ORGANIZATION AT
THIS TIME...AND DEVELOPMENT...IF ANY...WILL BE SLOW TO OCCUR.
ABUNDANT MID/UPPER LEVEL MOISTURE IS NOTED ON WATER VAPOR
IMAGERY BETWEEN THE TROUGH AXIS AND AN UPPER-LEVEL LOW SPINNING
NEAR THE FLORIDA KEYS. SCATTERED SHOWERS AND TSTMS ARE OVER THE
EASTERN GULF MAINLY ASSOCIATED WITH THE UPPER LOW. SCATTERED
SHOWERS ARE NEAR THE TROUGH AXIS WHICH IS FORECAST TO MOVE
ACROSS THE WESTERN GULF THROUGH TONIGHT. A RIDGE FROM THE ATLC
EXTENDS ACROSS THE FLORIDA PENINSULA INTO THE EASTERN GULF. THE
RIDGE ALSO DOMINATES THE SE CONUS. A DRYER AIR MASS IS NOTED
WEST OF THE SURFACE TROUGH.

CARIBBEAN SEA...
A BROAD AREA OF LOW PRESSURE LOCATED JUST EAST OF NICARAGUA
CONTINUES TO PRODUCE DISORGANIZED SHOWERS AND THUNDERSTORMS OVER
A LARGE PORTION OF THE SOUTHWESTERN CARIBBEAN SEA. A SURFACE
TROUGH IS ANALYZED IN THIS AREA EXTENDING FROM 20N85W TO 12N82W.
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED DUE TO
PROXIMITY TO LAND. HOWEVER...HEAVY RAIN WILL SPREAD OVER
PORTIONS OF CENTRAL AMERICA DURING THE NEXT COUPLE OF DAYS AS
THIS SYSTEM MOVES SLOWLY WESTWARD. ANOTHER SURFACE TROUGH
PERSISTS OVER THE NE CARIBBEAN STRETCHING FROM PUERTO RICO NE TO
22N62W. THIS TROUGH IS THE SURFACE REFLECTION OF AN UPPER-LEVEL
LOW CENTERED NEAR 22N64W. SCATTERED SHOWERS WITH EMBEDDED TSTMS
ARE NEAR THE TROUGH AXIS AFFECTING PUERTO RICO AND COASTAL
WATERS...PARTICULARLY ACROSS THE ATLC SIDE. A RAINFALL RECORD
WAS SET TODAY AT THE SAN JUAN INTERNATIONAL AIRPORT WITH 1.73
INCHES OF RAIN. THIS BROKE THE OLD RECORD OF 0.98 INCHES SET
BACK IN 1957. THE UPPER LOW IS FORECAST TO BRING ACTIVE WEATHER
TO PUERTO RICO AND THE VIRGIN ISLANDS THIS SATURDAY.

ATLANTIC OCEAN...
ALOFT...AN UPPER-LEVEL LOW IS SPINNING NEAR THE FLORIDA KEYS
WITH THE CYCLONIC FLOW COVERING FLORIDA...CUBA AND THE BAHAMAS
MAINLY W OF 76W. AS PREVIOUSLY MENTIONED...ANOTHER UPPER LEVEL
LOW IS NEAR 22N64W HELPING TO INDUCE CONVECTION NEAR PUERTO
RICO. IN BETWEEN...THERE IS AN UPPER-LEVEL RIDGE EXTENDING S TO
NEAR THE SE BAHAMAS. A RIDGE ALSO THE TROPICAL ATLC. AT THE
SURFACE...RIDGING DOMINATES THE BASIN ANCHORED BY A SERIES OF
HIGHS CENTERED N OF THE DISCUSSION AREA. THE STRONGEST
ONE...ANALYZED 1028 MB...IS NEAR THE AZORES. PRES GRADIENT
BETWEEN THE AZORES HIGH AND LOWER PRES OVER AFRICA IS PRODUCING
AN AREA OF NLY WINDS IN THE 20 TO 25 KT RANGE BETWEEN THE CANARY
AND THE CAPE VERDE ISLANDS MAINLY E OF 20W. DRY SAHARAN AIR
LAYER ACCOMPANIED BY DUST COVERS MUCH OF THE TROPICAL ATLC
SUPPRESSING CONVECTION IN THIS REGION.

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

$$

GR




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