[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN JUL 13 2008

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURE....

TROPICAL STORM BERTHA IS CENTERED NEAR 30.0N 63.0W AT 13/1800
UTC ABOUT 165 NM SE OF BERMUDA AND IS STATIONARY. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 991 MB. THE MAXIMUM SUSTAINED WIND
SPEED IS 55 KT WITH GUSTS TO 65 KT. A TROPICAL STORM WARNING IS
IN EFFECT FOR BERMUDA. PLEASE READ THE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE
PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS.
BERTHA HAS BEEN MEANDERING FOR SOME TIME AS IT HAS BEEN EMBEDDED
IN WEAK STEERING CURRENTS...BUT A MOTION TO THE N-NW IS
ANTICIPATED OVER THE NEXT COUPLE OF DAYS. IR IMAGERY SHOWS
CONVECTION INCREASING SLIGHTLY IN THE NE QUADRANT BETWEEN 90 NM
AND 180 NM OF THE CENTER. THE W PERIPHERY OF THIS ACTIVITY IS
BEING DETECTED ON DOPPLER RADAR FROM BERMUDA AND IS CURRENTLY
ABOUT 80 NM SSE OF THE ISLAND. CONVECTION HAS CHANGED LITTLE IN
A BAND TO THE S AND SE OF THE CENTER...WITHIN 90-120 NM.

STRONG TROPICAL WAVE IS ALONG 37W/38W S OF 17N MOVING W 10-15
KT. A 1009 MB LOW IS ANALYZED ALONG THE AXIS NEAR 9N. VISIBLE
SATELLITE IMAGES SHOWS A LARGE WELL DEFINED ENVELOPE OF CYCLONIC
TURNING...FOCUSED NEAR THE LOW CENTER. SHIP TBWUK18 REPORTED 27
KT S WINDS SE OF THE LOW CENTER AT 12Z...UNFORTUNATELY BOTH
ASCAT AND QSCAT MISSED THE REGION. A LARGE AREA OF SCATTERED
MODERATE AND EMBEDDED ISOLATED STRONG CONVECTION IS WITHIN 240
NM W AND 60 NM E SEMICIRCLES. SIMILAR CONVECTION IS LOCATED
WITHIN THE INTERSECTION OF THE ITCZ FROM 4N-8N BETWEEN 36W-44W.
THIS SYSTEM HAS THE POTENTIAL TO BECOMING A TROPICAL DEPRESSION
DURING THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 56W/57W S OF 16N MOVING W 15 KT. SYNOPTIC
OBSERVATIONS FROM TRINIDAD AND TOBAGO...BARBADOS...ST LUCIA AND
OTHER ISLANDS ALL SHOW 24-H PRES FALLS OF ABOUT 3 MB IN
ASSOCIATION WITH THE APPROACH OF THE WAVE. THIS FEATURE HAS BEEN
WELL DEFINED FOR DAYS...HOWEVER ITS MOISTURE FIELD HAS FLATTENED
SOME TODAY BASED ON THE MIMIC TPW ANIMATION. SCATTERED SHOWERS
AND TSTMS ARE WITHIN 200 NM W OF THE WAVE S OF 12N AND E OF THE
AXIS FROM 10N-12N BETWEEN 49W-52W.

TROPICAL WAVE HAS BEEN ADJUSTED W ALONG 85W/86W S OF 20N MOVING
W 15 KT. THE UPDATED POSITION WAS MAINLY BASED ON THE SOUTHERN
PART OF THE WAVE IN THE EPAC WHERE A LOW PRESSURE SYSTEM HAS
FORMED. THAT LOW IS BEING MONITORED FOR DEVELOPMENT...REFER TO
THE EAST PACIFIC...TWDEP...FOR MORE DETAILS. LIKE THE WAVE TO
ITS E...24-H SLP FALLS ARE ABOUT 2-3 MB OVER THE YUCATAN
PENINSULA...HONDURAS AND OTHER PARTS OF CENTRAL AMERICA IN
ASSOCIATION WITH THE WAVE AND DEVELOPING LOW. SFC PRESSURE FALLS
ARE OF SIMILAR MAGNITUDE OVER CUBA...BUT THIS COULD ALSO BE
ASSOCIATED WITH TROUGHING OVER FLORIDA AND THE E GULF. SCATTERED
MODERATE CONVECTION IS S OF 15N W OF 78W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N14W 10N26W 11N34W 8N39W 9N55W.
SCATTERED MODERATE CONVECTION IS WITHIN 150 NM N OF THE AXIS
BETWEEN 19W-21W AND FROM 4N-7N BETWEEN 13W-19W.

...DISCUSSION...

THE GULF OF MEXICO...
AN UPPER RIDGE CENTERED OVER TEXAS AND AN UPPER LOW OVER THE
BAHAMAS IS INDUCING NE TO E FLOW ALOFT OVER THE GULF. A
MID-LEVEL PERTURBATION OR SHORTWAVE COMBINED WITH THE TAIL END
OF A SFC TROUGH FROM NEAR ST AUGUSTINE FLORIDA TO 24N88W IS
TRIGGERING SCATTERED SHOWERS AND TSTMS WITHIN 75 NM OF A NW-SE
LINE FROM 30N80W TO 25N82W. SCATTERED SHOWERS AND ISOLATED TSTMS
ARE OCCURRING IN THE BAY OF CAMPECHE IN THE VICINITY OF A SMALL
UPPER LOW CENTERED NEAR 20N95W. OTHERWISE...STABLE AIR ALOFT W
OF 90W AND WEAK SFC HIGH PRES CENTERED NEAR 27N92W IS PROVIDING
THE REMAINDER OF THE AREA WITH LIGHT WINDS AND FAIR WEATHER.

THE CARIBBEAN SEA...
UPPER DIFFLUENCE BETWEEN TROUGHING OVER E CUBA/JAMAICA AND A
FLAT RIDGE ALONG 12N W OF 70W IS PRODUCING A LARGE AREA OF
SCATTERED SHOWERS AND TSTMS S OF 15N W OF 76W. LOW-LEVEL
CONVERGENCE ASSOCIATED WITH THE ITCZ AND ENHANCED LIFT BY A
TROPICAL WAVE ALONG 86W IS CONTRIBUTING TO THE AFOREMENTIONED
TSTM ACTIVITY. ANOTHER TROPICAL WAVE IS APPROACHING THE LESSER
ANTILLES WITH THE W PERIPHERY OF THE DEEPER SCATTERED SHOWERS
AND TSTMS NEARING TRINIDAD AND TOBAGO. THE REMAINDER OF THE E
CARIBBEAN IS FAIRLY TRANQUIL AS A SUBSIDENT ENVIRONMENT IS IN
PLACE. THIS IS CAPPING THE TYPICAL QUICK MOVING STREAMS OF
LOW-LEVEL SHOWERS. TRADE WINDS ARE ON THE STRONG SIDE (20-25 KT)
OVER THE S CENTRAL CARIBBEAN AND THESE WINDS WILL LIKELY CHANGE
LITTLE OVER THE NEXT COUPLE OF DAYS.

THE ATLANTIC OCEAN...
A WEAK FRONT OR TROUGH EXTENDS OFF THE SE U.S. COAST FROM A 1012
MB LOW NEAR 32N78W ACROSS NE FLORIDA AND INTO THE GULF OF
MEXICO. WHILE MUCH OF THE SHOWER ACTIVITY ASSOCIATED WITH THE
FRONTAL LOW HAS DIMINISHED...IT IS BEING MONITORED FOR THE
POSSIBILITY OF DEVELOPMENT. AN UPPER LOW SITUATED OVER THE NE
BAHAMAS NEAR 25N76W IS PRODUCING A FAIR AMOUNT OF CLOUDINESS AND
LIGHTNING DATA INDICATES A SMALL AREA OF TSTMS BETWEEN SE
FLORIDA AND THE NW BAHAMAS.

ELSEWHERE...BESIDES FOR BERTHA AND THE TROPICAL WAVES...THE
REMAINDER OF THE DISCUSSION ZONE IS DEVOID OF SIGNIFICANT DEEP
CONVECTION. THE MID AND UPPER PATTERN CONSISTS OF AN UPPER
TROUGH TO BERTHA'S E ALONG 42W N OF 18N WITH AN ASSOCIATED WEAK
SFC BOUNDARY ANALYZED FROM 32N46W TO 28N51W. SCATTERED SHOWERS
ARE POSSIBLE WITHIN 120 NM OF THE SFC TROUGH. BROAD RIDGING
COVERS MUCH OF THE E ATLC WITH THE RIDGE AXIS ALONG 19N/20N AND
ANOTHER HIGH NEAR 16N50W. UPPER CONFLUENCE IS DRYING THE
ATMOSPHERE N OF 23N E OF 35W. IN THE LOWER LEVELS...SFC RIDGING
DOMINATES MUCH OF THE PATTERN EXTENDING S AND SW FROM A 1029 MB
HIGH NEAR THE AZORES. A WEAK TROUGH WAS WELL DETECTED IN THE
ASCAT DATA FROM 26N26W TO 31N28W PRODUCING A FEW SHOWERS AND
INCREASING E WINDS TO 20 KT WITHIN 180 NM E OF THE AXIS. SFC
REPORTS FROM THE LESSER ANTILLES AND THE HAZY LOOK ON VISIBLE
IMAGES ACROSS THE TROPICAL ATLC...SUGGEST THE PRESENCE OF
SAHARAN DUST S OF 25N E OF 62W.

$$
CANGIALOSI




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