[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 072332
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE AUG 07 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 29W/30W S OF 13N MOVING W NEAR 10 KT.
THIS LOW AMPLITUDE FEATURE IS POORLY DEFINED WITH THE AXIS
PLACED ALONG SLIGHT MID-LEVEL TURNING NEAR 9N. THERE IS A MORE
PRONOUNCED ROTATION NEAR 11N35W. AT THIS POINT...IT'S DIFFICULT
TO SAY IF THAT ROTATION IS ASSOCIATED WITH THIS WAVE OR JUST
INSTABILITY WITHIN THE ITCZ. DECIDED TO HOLD CONTINUITY FOR THIS
MAP BASED ON THE MET-9 HOVMOLLER DIAGRAMS...BUT WILL BE
REASSESSED AT 00Z. CONVECTION IS FAIRLY MINIMAL AND CONFINED TO
THE ITCZ W OF THE ANALYZED AXIS.

HIGH AMPLITUDE TROPICAL WAVE IS TILTED ALONG 20N44W TO 6N40W
MOVING W 10-15 KT. YESTERDAY AT THIS TIME...THE WAVE WAS DRAWN
EVEN MORE AMPLIFIED WITH THE NRN BRANCH APPROACHING 28N. SINCE
THEN...SAT IMAGERY AND THE UW-CIMSS TPW PRODUCT SHOWED THE
SPLITTING OF THIS FEATURE WITH THE NRN PORTION PULLING OFF TO
THE NW. THE WAVE CONTINUES TO EXHIBIT A LARGE INVERTED V SHAPE
IN THE SURROUNDING STRATOCUMULUS CLOUDS. ISOLATED MODERATE
CONVECTION REMAINS CONFINED TO WHERE THE SRN PORTION OF THE AXIS
INTERSECTS WITH THE ITCZ FROM 10N-14N BETWEEN 40W-45W.

TROPICAL WAVE IS ALONG 52W/53W S OF 16N MOVING W NEAR 10 KT.
THIS WAVE REMAINS CHALLENGING TO LOCATE WITH THE CURRENT PSN
BASED MOSTLY ON FORWARD EXTRAPOLATION. SHOWER AND TSTM ACTIVITY
IS CONFINED TO THE ITCZ.

TROPICAL WAVE IS IN THE CENTRAL CARIB ALONG 75W S OF 19N MOVING
W 10-15 KT. THE EXACT PSN IS DIFFICULT TO LOCATE AS THERE IS
LITTLE SIGNATURE SEEN ON SATELLITE OR IN SFC OBS. THE ONLY
SOURCE THAT SUPPORTS THIS WAVE ATTM IS A MOISTURE SURGE EVIDENT
IN THE UW-CIMSS TPW FIELD. THERE IS SOME DEBATE THAT THIS WAVE
COULD BE FURTHER E IN THE E CARIB WHERE THERE IS LOW-LEVEL
TROUGHING AND SHOWER ACTIVITY. FOR NOW WE DECIDED TO HOLD
FORWARD CONTINUITY ANALYZING THE OTHER FEATURE AS A TROUGH ON
THE SFC MAP. MORE ON THIS IN THE CARIBBEAN SECTION BELOW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 15N17W 11N30W 13N38W 11N48W 12N61W.
BESIDES FOR THE CONVECTION DISCUSSED IN THE TROPICAL WAVES
SECTION...SCATTERED MODERATE IS WITHIN 90 NM OF THE AXIS W OF
51W.

DISCUSSION...

GULF OF MEXICO...
CONTINUED QUIET WEATHER EXISTS IN THE GULF OF MEXICO. UPPER ELY
FLOW IS FAIRLY UNIFORM ACROSS THE REGION BETWEEN A STRONG UPPER
HIGH OVER THE SRN APPALACHIANS AND INVERTED TROUGHING OVER THE
YUCATAN PENINSULA. SCATTERED SHOWERS AND TSTMS HAVE FIRED UP
THIS AFTERNOON ACROSS THE FL PANHANDLE...SRN ALABAMA AND
MISSISSIPPI TRIGGERED BY A WEAK LOW-LEVEL TROUGH. MUCH OF THIS
ACTIVITY HAS NOW MOVED INTO THE NRN GULF WATERS N OF 28N BETWEEN
85W-92W STEERED BY THE STRONG UPPER ELY FLOW. FOR THE MOST
PART...THE REMAINDER OF THE GULF IS RELATIVELY QUIET WITH ONLY
ISOLATED ACTIVITY. THE SFC PATTERN HAS CHANGED LITTLE SINCE
YESTERDAY WITH A 1018 MB HIGH CENTERED NEAR 27N92W. THIS WEAK
GRADIENT IS ALLOWING WINDS TO BE LIGHT AND SEAS LOW. LITTLE
CHANGE IN THE SFC AND MOISTURE PATTERN IS EXPECTED OVER THE NEXT
COUPLE OF DAYS.

CARIBBEAN SEA...
THE CARIB IS SLIGHTLY MORE ACTIVE THAN THE GULF...BUT STILL
LACKS ANY FEATURE WITH MUCH ORGANIZATION. EARLIER TODAY...A
LOW-LEVEL TROUGH WAS ADDED TO THE MAP IN THE E CARIB CURRENTLY
ANALYZED N OF PUERTO RICO TO THE SRN WINDWARDS ALONG 22N67W
16N66W 10N61W. AS MENTIONED IN THE TROPICAL WAVE SECTION...WE
DECIDED NOT TO BACK-UP THE WAVE IN THE CENTRAL CARIB TO THIS
VAGUE TROUGHINESS BASED ON INCONCLUSIVE DATA. DISORGANIZED
SHOWERS AND ISOLATED TSTMS COVER THE ERN ISLANDS ROUGHLY FROM
PUERTO RICO SEWD. HIGH LEVEL CLOUDS AND ISOLATED SHOWERS/TSTMS
LIE S OF 16N W OF 70W. THIS MOISTURE IS BEING DRAWN NWWARD BY
INVERTED TROUGHING OVER THE YUCATAN PENINSULA. ELSEWHERE
...RELATIVELY QUIET CONDITIONS PREVAIL WITH THE EXCEPTION OF
TYPICAL LAND/MOUNTAINOUS TSTM ACTIVITY OVER MANY OF THE ISLANDS
AND QUICK MOVING SHALLOW SHOWERS OVER THE SEA. TRADE WINDS
REMAIN RATHER LIGHT ACROSS THE REGION. THESE WINDS ARE
ANTICIPATED TO INCREASE SLIGHTLY IN THE ERN/CENTRAL CARIB TOWARD
THE END OF THE WEEK.

ATLANTIC OCEAN...
LINGERING VERY WEAK SFC TROUGHING EXTENDS ACROSS THE WRN ATLC
FROM A 1015 MB SFC LOW NEAR 34N71W TOWARD THE WRN BAHAMAS NEAR
27N76W. THIS WEAK BOUNDARY...CONSISTING OF ONLY WEAK LOW LEVEL
TURNING...IS LOSING SUPPORT FROM UPPER TROUGHING TO ITS E WITH
THE AXIS EXTENDING FROM 32N63W TO AN UPPER LOW NEAR 25N68W.
UPPER DIFFLUENCE AND SOME INFLUENCE FROM THE LOW-LEVEL BOUNDARY
IN THE E CARIB IS PRODUCING A GOOD AMOUNT OF CLOUDINESS AND
SCATTERED SHOWERS/ISOLATED TSTMS BETWEEN 58W-67W. THE REMAINDER
OF THE UPPER PATTERN CONSISTS OF TWO HIGHS...ONE CENTERED IN THE
DEEP TROPICS NEAR 14N58W AND THE OTHER NEAR 20N35W. SHARP HIGHLY
ELONGATED TROUGHING LIES BETWEEN THESE HIGHS ALONG 46W. THIS
SYSTEM IS ONLY PRODUCING A PLUME OF CIRRUS IN ITS VICINITY. A
STRONGER TROUGH COVERS THE NE PORTION OF THE AREA HELPING TO
ENHANCE DRY STABLE AIR ALOFT E OF 28W.

THE REMAINDER OF THE SFC PATTERN IS DOMINATED BY A 1031 MB HIGH
W OF THE AZORES NEAR 38N37W. LIGHT TO MODERATE ELY TRADES ARE
THE RULE ACROSS THE MAJORITY OF THE REGION...EXCEPT E OF ABOUT
30W WHERE QSCAT SHOWS 20-30 KT NELY WINDS DUE TO THE TIGHTENED
GRADIENT BETWEEN THE HIGH AND MUCH LOWER PRESSURES OVER AFRICA.
WIDESPREAD STABLE LOW-LEVEL AIR...PARTLY ASSOCIATED WITH SAHARAN
DUST...IS LOCATED TO THE E OF THE HIGH AMPLITUDE WAVE IN THE
CENTRAL ATLC.

$$
CANGIALOSI


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