GOM: INVEST 90L

[hurricanefloyd5]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
320 PM EDT MON MAY 18 2009

.DISCUSSION...

...MUCH NEEDED WIDESPREAD RAINFALL FELL ACROSS THE CWA TODAY...AND
MORE IS ON THE WAY THROUGH MID-LATE WEEK...

...VERY HAZARDOUS BOATING AND BEACH CONDITIONS WILL DEVELOP OVER THE
ATLANTIC AS LOW PRESSURE SPINS UP SOUTH OF FLORIDA...

TONIGHT/TUE...FRONTAL BOUNDARY WILL REMAIN STALLED OVER THE AREA
TONIGHT INTO TOMORROW KEEPING A VERY MOIST AIRMASS ON PLACE. IN
ADDITION TO THIS...THE UPPER LEVEL TROUGH OVER THE AREA WILL BEGIN
TO FORM INTO A CUTOFF LOW PRESSURE SYSTEM WHICH WILL KEEP TEMPS COOL
ALOFT AND THE WEATHER PATTERN UNSETTLED. THEREFORE WILL KEEP LIKELY
POPS (60-70 PERCENT) OVER THE AREA. CLOUD COVER WILL LIMIT
INSTABILITY OVER THE AREA SO WILL ONLY MENTION A CHANCE FOR
THUNDERSTORMS. STRONGER STORMS WILL CONTINUE TO BE ABLE TO PRODUCE
LOCALIZED HEAVY RAINFALL WITH RAINFALL RATES UP TO ONE TO TWO INCHES
PER HOUR. TIGHTER PRESSURE GRADIENT OVER NORTHERN SECTIONS OF THE
CWA WILL KEEP WINDS ELEVATED OVERNIGHT UP TO 10 TO 15 MPH OUT OF THE
NORTHEAST. THESE WINDS COULD CONTINUE BECOME STRONGER INTO TOMORROW
DEPENDING ON DEVELOPMENT OF A LOW PRESSURE SYSTEM SOUTH OF THE AREA
HOWEVER MODELS ARE CONTINUING TO HAVE A HARD TIME RESOLVING THIS
FEATURE SO WILL KEEP WINDS AS IS FOR NOW.

TUE NGT-WED NGT...CONTINUE TO FAVOR THE MORE WWD ECM/UKM SOLNS OVER
THE GFS (WHICH SEEMS TO OVERDEVELOP THE WEAK LOW JUST NORTH OF THE
ERN CUBA COAST) AND THE NAM (WHICH LOOKS TOO LOW WITH THE CTRL PRES
OVER FL. HENCE...EXPECT BEST PRES FALLS/SFC CYCLOGENESIS WILL OCCUR
CLOSER TO THE MID-UPR CUTOFF LOW CTR...WHERE VERTICAL ASCENT WILL BE
STRONGEST. SYSTEM WILL GRDLLY SPIN UP AND THEN BE SLOW TO DRIFT WWD
INTO THE GOMEX. TIGHTENING PGRAD COUPLED WITH HIGH PWAT VALUES INVOF
DECAYED/WASHED OUT FRONTAL BDRY WILL KEEP ECFL IN A VERY MOIST AND
UNSETTLED WX REGIME...WITH FAIRLY WDPRD COVRG OF RAINFALL THROUGH AT
LEAST WEDNESDAY NGT. BRISK EASTERLIES MAY GIVE A "SQUALLY" TYPE FEEL
TO THE WX AS SHRA BANDS EMBEDDED WITHIN WDSPRD STRATIFORM RAINFALL
REPEATEDLY MOVE ONSHORE.

THU-SUN...(PREV) FCST WILL HINGE LARGELY ON HOW THE ANTICIPATED LOW
PRESSURE SYSTEM DEVELOPS AND INTERACTS WITH THE FRONTAL TROF AND THE
SURROUNDING MOISTURE FIELD. GIVEN THE NUMBER OF ELEMENTS IN PLAY AND
THE FACT THE LOW IS STILL MORE OR LESS AN OPEN WAVE...WILL MAKE ONLY
MINOR ADJUSTMENTS TO THE PREVIOUS EXTENDED FCST. EXPECT TO GRADUALLY
TREND TWDA MORE DIURNAL-DRIVEN CONVECTIVE REGIME WITH POPS REMAINING
MORE TYPICAL OF LATE JUNE/EARLY JULY RATHER THAN MID-LATE MAY.

[Evil Jeremy]

Really, shouldnt most of the recent posts in this topic be in the Florida weather discussion thread in the other part of the forum?

[AdamFirst]

Really, shouldnt most of the recent posts in this topic be in the Florida weather discussion thread in the other part of the forum?

Well, 90L could be involved relatively soon.

[jlauderdal]

Excellent NWS Miami discussion recently posted:

000
FXUS62 KMFL 181830
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
230 PM EDT MON MAY 18 2009

.DISCUSSION...
CURRENTLY...STRONG LATE-SEASON MID/UPPER TROUGH CONTINUES TO DIG S
ACROSS THE ERN GULF OF MEXICO AND IS ABOUT TO CLOSE OFF JUST W OF
THE SW FL COAST. A WEAKENING SFC COLD FRONT OR TROUGH IS LOCATED
N OF LAKE OKEECHOBEE AND IS SAGGING SE...BUT EXACT LOCATION IS
TOUGH TO DETERMINE DUE TO WIDESPREAD CONVECTION. A SECOND MID
LEVEL LOW...WITH PSBL WEAK SFC REFLECTION IS LOCATED BETWEEN CENTRAL CUBA
AND THE BAHAMAS AND MOVING NORTHWARD. LOCALLY...THUNDERSTORMS HAVE
DEVELOPED ACROSS MUCH OF THE INTERIOR THIS AFTERNOON WITH A SLOW
NORTHWARD MOVEMENT...AND OTHER THUNDERSTORMS ARE LINED UP IN THE
GULF OFFSHORE COLLIER COUNTY MOVING EAST.

MODEL GUIDANCE CONTINUES TO STRUGGLE WITH THE EVOLUTION OF THIS
COMPLEX WEATHER PATTERN THE NEXT SEVERAL DAYS...BEGINNING TONIGHT.
THE BIGGEST QUESTION SEEMS TO BE WHERE EXACTLY A MID/UPPER LOW WILL
CLOSE/CUT OFF ACROSS THE REGION...AND WHAT IF ANY INTERACTION THERE
WILL BE WITH THE SYSTEM COMING NORTH FROM CUBA. THE 06Z/12Z GFS/00Z
ECMWF/00Z NAM ALL CLOSED THE MID LEVEL SYSTEM OFF FROM THE DIGGING
GULF TROUGH OVER THE FL WEST COAST OR ERN GULF...WITH A WEAK SFC LOW
REFLECTION DEVELOPING BENEATH TO FORM A STACKED SYSTEM. THE 12Z NAM
HOWEVER HAS CHANGED ITS MIND AND MADE THE ERN MID-LEVEL SYSTEM
DOMINANT AS IT COMES NORTH OUT OF CUBA AND INTERACTS WITH THE
DIGGING GULF TROUGH...TAKING A STRONGER SFC LOW INTO ECENTRAL FL
AS OPPOSED TO ACROSS SOUTH FL OR OFF THE WEST COAST. THE 12Z GFS
CONTINUES ITS DIFFICULTY RESOLVING THIS PATTERN WITH 2 WEAK SFC
LOWS...AND THE ONE DEVELOPING OVER THE SE BAHAMAS AND MOVING NW
TOWARDS ECENTRAL FL BEING THE DOMINANT ONE...THOUGH THIS COULD BE
POSSIBLE IF THE ERN LOW N OF EASTERN CUBA HOLDS TOGETHER AS MID-
LEVEL LOW CUTS OFF NEAR SOUTH FL. SEEMS LIKE THE KIND OF SITUATION
WHERE WE DON`T KNOW EXACT DETAILS UNTIL THE SCENARIO PLAYS OUT.

INITIALLY FOR TONIGHT...AS THE ERN GULF TROUGH DIGS MODELS DO AGREE
THAT WEAKENING SFC BOUNDARY/TROUGH WILL SAG SE TO SOMEWHERE ACROSS
SOUTH FL...PERHAPS AS FAR AS THE SERN METRO AREAS AS AT LEAST
WEAK/BROAD SFC LOW PRESSURE FORMS NEAR THE FL STRAITS. EXCELLENT
UPPER DIVERGENCE AHEAD OF THIS...AS WELL AS LOW LEVEL MOISTURE SURGE
AND INCREASING SFC CONVERGENCE DUE TO INCREASING ONSHORE FLOW SHOULD
LEAD TO A SETUP FOR HEAVY RAINFALL SOMEWHERE ACROSS THE CWA.
LOCATION OF THE HEAVIEST RAINFALL IS STILL SOMEWHAT UNCERTAIN AT
THIS POINT AS IT DEPENDS JUST EXACTLY WHERE THE STALLED BOUNDARY
SETS UP AND FOCUSES THE STRONGEST CONVERGENCE AND POSSIBLE TRAINING
OF ANY CONVECTION...THOUGH THE SOUTHEAST COAST WOULD BE A FAVORED
PLACE FOR THIS TO OCCUR DUE TO COASTAL CONVERGENCE. A LOT THROUGH
TOMORROW ALSO DEPENDS ON WHERE THE MID LEVEL LOW CUTS OFF.
OVERALL...WILL NOT MAKE MANY CHANGES TO THE GOING FCST AS POPS ARE
ALREADY HIGH. GIVEN THE INCREASING SFC CONVERGENCE...GOOD UPPER
DIVERGENCE...WARM CLOUD DEPTH OF 4KM FROM LATE TONIGHT THROUGH
TOMORROW AND PWATS APPROACHING 2 INCHES BENEFICIAL AND HEAVY
RAINFALL IS A GOOD BET...ESPECIALLY ALONG THE WEAKENING BOUNDARY
AND SOUTHEASTERN COAST.

BY MID/LATE WEEK...THE LARGE CUTOFF SYSTEM WILL TAKE ITS TIME MOVING
AWAY...BUT MOST GUIDANCE AGREES ON A SLOW WESTWARD DRIFT THIS
PERIOD. THIS WOULD LEAVE SOUTH FL IN A RATHER HUMID AND TROPICAL
AIRMASS WITH DEEP-LAYERED SERLY FLOW...MAKING AT LEAST SCATTERED DAILY
CONVECTION A GOOD BET

http://forecast.weather.gov/product.php ... glossary=1

I love these guys... follow that bold sentence for the next 24hours..

they said this morning they were going to come off the fence, well one leg on one leg off so we are making progress since saturdays vertically stacked disco

[NEXRAD]

could we see Tropical storm watches/warning for a SubTropical Storm for the florida's East Coast??????????/

I doubt it. The system would have to ramp-up really fast for such to occur. Even if the low deepens as much as the aggressive NAM, the system would have peak sustained winds in the 35 to 45 knot range over water. Such winds would translate to sustained 20 to 30 knots on land (esp. near the coast) with periodic gale-force gusts. Winds of that magnitude could be handled by local wind advisories as opposed to tropical storm warnings.

- Jay

[TropicalWXMA]

Latest sat. image/track from NRL Monterey:

[KWT]

As has been said this is a complicated set-up, like seemingly quite a few pre/early season systems that develop.

[Evil Jeremy]

Dual lows at 18 hours in the new GFS run:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _018.shtml

[TropicalWXMA]

1. SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT AN AREA OF
DISTURBED WEATHER HAS FORMED OVER EASTERN CUBA...THE SOUTHEASTERN
BAHAMAS...AND THE ADJACENT WATERS. SLOW DEVELOPMENT OF THIS SYSTEM
IS POSSIBLE DURING THE NEXT DAY OR TWO AS IT MOVES GENERALLY
NORTHWARD AT 10 TO 15 MPH. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT WILL INVESTIGATE THE SYSTEM ON TUESDAY...IF NECESSARY.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Any word on this?

[Evil Jeremy]

This new GFS run shows an even weaker system than before.

[RL3AO]

1. SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT AN AREA OF
DISTURBED WEATHER HAS FORMED OVER EASTERN CUBA...THE SOUTHEASTERN
BAHAMAS...AND THE ADJACENT WATERS. SLOW DEVELOPMENT OF THIS SYSTEM
IS POSSIBLE DURING THE NEXT DAY OR TWO AS IT MOVES GENERALLY
NORTHWARD AT 10 TO 15 MPH. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT WILL INVESTIGATE THE SYSTEM ON TUESDAY...IF NECESSARY.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

Any word on this?

We'll find out tomorrow. Unless it really gets its act together, I don't see a reason for it to go.

[Category 5]

I've been busy all day (flying to florida) but from what I've seen so far this becoming Ana is a longshot at best. Certainly stranger things have happened though.

Its certainly making my vacation a little more interesting.

Trying to escape all of the frost and freeze warnings for much of the NE US?

Right now, its cooler here (57) then at my house (59)

However, that wont hold up tonight.

[Rainband]

it's just going to be rain, that's good news

[MGC]

I don't see 90L doing much, doubt it becomes a depression. UL condition are not that condusive to development. If anothe low forms in the GOM under the ULL then I expect it to become the dominate system. 90L should move inland near the Cape and be absorbed by the GOM low. Just my 2 cents.....MGC

[cpdaman]

it looks like it died to me.........eyes on gulf/straits

[boca]

The area by 25n and 84.5w is the area I'm looking at.It looks better on sat than 90L.

http://metofis.rsmas.miami.edu/~dortt/s ... 1_loop.gif

[NEXRAD]

The area by 25n and 84.5w is the area I'm looking at.It looks better on sat than 90L.

http://metofis.rsmas.miami.edu/~dortt/s ... 1_loop.gif

This general location coincides reasonably well with a surface low indicated by the HPC in their 18Z and 1930Z surface analysis.

- Jay

[boca]

One of the local channels said that the two lows would move towards each other crossing S FL. I find that interesting since low pressures can't move towards each other,but the Fujiwanna effect would take place,not in this instance though.

[cycloneye]

18z UKMET tracks thru Central Florida reaching the northern gulf.

[Rainband]

One of the local channels said that the two lows would move towards each other crossing S FL. I find that interesting since low pressures can't move towards each other,but the Fujiwanna effect would take place,not in this instance though.

i think that that's a station I wouldn't tune into