ATL: TROPICAL DEPRESSION BONNIE - DISCUSSION

[cycloneye]

First recon mission is slated for tommorow afternoon with departure around 10:00 AM EDT.See rest of the TCPOD at recon thread. viewtopic.php?f=59&t=108625&p=2015328#p2015328

[tolakram]

Recent wind shift to the southwest: http://www.wunderground.com/weatherstat ... ?ID=MCLBP4

Overview: http://www.wunderground.com/wundermap/? ... .7&zoom=10

[floridasun78]

Recent wind shift to the southwest: http://www.wunderground.com/weatherstat ... ?ID=MCLBP4

Overview: http://www.wunderground.com/wundermap/? ... .7&zoom=10

what that mean? sw wind

[gatorcane]

The bottom line is that as long as that ULL/TUTT feature is to the west, 97L will have a hard time doing more than it's doing now...

http://www.goes.noaa.gov/HURRLOOPS/huwvloop.html

P.S. The WV is my favorite loop, because it can show what the other loops cannot, and it's those "invisible" factors that make all the difference...

Mine as well, and I agree 100%.

Looking at the WV loop, I don't see that the ULL is creating that much shear over 97L. It seems to have weakened quite a bit. There is some shear out of the WSW, but conditions aren't that bad for 97L to develop gradually.

[Frank2]

what that mean? sw wind

In the tropics in the northern hemisphere, a surface observation with a SW wind can sometimes mean a counterclockwise (low pressure) circulation to the northwest - but it can also be due to thunderstorms in the area...

Really, it doesn't mean that much if only one station is reporting SW winds for one observation - a low pressure center at the surface would generate SW winds over a large area (the low pressure center would be to the northwest, so the station with the SW wind in this case would be at the "5 o'clock" position)...

[dolebot_Broward_NW]

poof -

You don't see the upper level clouds move because the cloud tops haven't reached the upper atmosphere yet, they have condensed out by that point. I also see the ULL to the systems NNW here:

http://www.goes.noaa.gov/HURRLOOPS/huwvloop.html

The ULL is helping ventilate any storms, watch the fast moving sea-storms to 97L's north. Recall that shear is a delta between 2 levels in the atmosphere, i.e. surface moves West while upper remains idle = shear. This provides the upper level divergence needed.

[MiamiHurricanes10]

TAFB surface analysis shows that 97L is forecasted to develop an area of low pressure within 24 hours.

[gatorcane]

000
FXUS62 KMFL 201442
AFDMFL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MIAMI FL
1042 AM EDT TUE JUL 20 2010

...DANGEROUS, LIFE-THREATENING RIP CURRENTS ATLANTIC BEACHES...
...WATCHING VIGOROUS TROPICAL WAVE NEAR PUERTO RICO FOR POSSIBLE HEAVY
RAIN/GUSTY WINDS FRI-SAT...

.UPDATE...FORECAST IS ON TRACK AND SO NO CHANGES LOOK NECESSARY.
STRONG EASTERLY WIND FLOW CONTINUES...RESULTING IN DANGEROUS RIP
CURRENTS AT THE ATLANTIC BEACHES. THIS WILL ALSO NOT ALLOW A GULF
BREEZE TO DEVELOP...ALLOWING TEMPS TO AGAIN SOAR FOR THE NAPLES
AREA...POSSIBLY TOWARDS THE RECORD OF 95 TODAY. NAPLES HAS HIT 95
FOR 3 STRAIGHT DAYS NOW! HOT PATTERN CONTINUES FOR THE GULF COAST.
DRY WEATHER WILL PREVAIL...WITH JUST THE POSSIBILITY FOR A FEW
SHOWERS OR STORMS.

NHC IS MONITORING THE VIGOROUS TROPICAL WAVE NEAR PUERTO RICO FOR
POSSIBLE TROPICAL CYCLONE DEVELOPMENT. REGARDLESS OF
DEVELOPMENT...THERE IS THE POTENTIAL FOR HEAVY RAIN/GUSTY WINDS
ACROSS SOUTH FL IN THE FRI-SAT TIME FRAME...WITH FOCUS
LOOKING LIKE FRIDAY. HAVE INCLUDED THIS IN THE HAZARDOUS WEATHER
OUTLOOK. FORECAST DETAILS WILL BE MORE PINNED DOWN IN THE COMING
DAYS...AND OF COURSE IS ALL DEPENDENT ON WHETHER OR NOT THIS WAVE
DEVELOPS. SINCE YESTERDAY...THE TREND IS TOWARDS DEVELOPMENT AND
SO THIS WILL BE WATCHED CLOSELY. /GREGORIA
http://forecast.weather.gov/product.php ... glossary=1

[poof121]

poof -

You don't see the upper level clouds move because the cloud tops haven't reached the upper atmosphere yet, they have condensed out by that point. I also see the ULL to the systems NNW here:

http://www.goes.noaa.gov/HURRLOOPS/huwvloop.html

The ULL is helping ventilate any storms, watch the fast moving sea-storms to 97L's north. Recall that shear is a delta between 2 levels in the atmosphere, i.e. surface moves West while upper remains idle = shear. This provides the upper level divergence needed.

Okay, that does make sense. So, which way is the vector subtraction done for the wind shear products, upper - lower, or lower - upper? Upper - lower makes sense here because of the direction the lower levels are moving.

Thanks.

[Blown Away]

97L is still a big giant mess, but this is the best it has looked so far. If you back away from the floater and look at the wide view you can clearly see an organizing system, convection is now trying to wrap around the NW side of the circulation, which tells me the ULL's effects are diminishing. Looks good, maybe Code Red at 2pm. Let the Orange and Red arguements begin.

[Stormcenter]

I'm not impressed at all with 97L right now.

[bvigal]

what that mean? sw wind

In the tropics in the northern hemisphere, a surface observation with a SW wind can sometimes mean a counterclockwise (low pressure) circulation to the northwest - but it can also be due to thunderstorms in the area...

Really, it doesn't mean that much if only one station is reporting SW winds for one observation - a low pressure center at the surface would generate SW winds over a large area (the low pressure center would be to the northwest, so the station with the SW wind in this case would be at the "5 o'clock" position)...

Thanks Frank, that is such an important point to make. It always pays to look at radar, if available, and Culebra having some nasty tstorms this morning.

[PTrackerLA]

Not that impressed either but the storms just E of Puerto Rico have the look of "something" trying to get better organized. Hopefully this doesn't develop and/or stay out at sea, of course I have a beach trip to the panhandle of Florida planned this weekend!

[rockyman]

This IR image (which can be misleading) points to a "center" forming off the NE tip Hispaniola:

[AdamFirst]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
331 AM EDT TUE JUL 20 2010

.DISCUSSION...


FRI-TUE...MODELS DIFFER ON EVOLUTION OF TROPICAL WAVE CURRENTLY
VICINITY OF PUERTO RICO. THE GFS IS OUT ON ITS OWN SHOWING A WEAK
LOW MOVING INTO CENTRAL FLORIDA ON SAT AND INSTEAD PREFER THE
ECMWF WHICH SHOWS A SPOT LOW PASSING THROUGH THE FLORIDA STRAITS
AND INTO THE SOUTHEAST GULF BY LATE FRI AS THE STOUT ATLANTIC
RIDGE HOLDS VICINITY OF 30N. THIS WOULD KEEP THE AREA IN AN
EAST/SOUTHEAST FLOW THROUGH THE WEEKEND WITH AN INFLUX OF DEEPER
MOISTURE STARTING FRI OR SAT WITH HIGHER POPS FOR A FEW DAYS.


New AFD has no mention of the wave.

[MWatkins]

Not that impressed either but the storms just E of Puerto Rico have the look of "something" trying to get better organized. Hopefully this doesn't develop and/or stay out at sea, of course I have a beach trip to the panhandle of Florida planned this weekend!

Good point on the structure. I was just looking at the latest visible images, and the clouds are starting to stretch out in bands instead of being clustered in blobs like yesterday.

What I will be watching today is to see if those bands take on more of a curved appearance.

Also, I was interested in that complex you pointed out sitting just east of Puerto Rico. It appears like it's trying to "curl" around to the south and even southwest, but it's hard to tell if that's really happening, or if it's just one of those satellite optical illusions. Just need to give it a little more time.

Regardless, the overall system appears to be better organized than yesterday. Deep convection has dissipated for now, but I would look to see it start to regenerate in the band-like structures as the day moves on.

The ULL seems to be weakening as well...

MW

[MGC]

looks like there might be a good bit of shear ahead of the future track of this system. Looks to be slowly getting a bit better organized. Still gonna need some time to develope a surface circulation..MGC

[Dean4Storms]

Not that impressed either but the storms just E of Puerto Rico have the look of "something" trying to get better organized. Hopefully this doesn't develop and/or stay out at sea, of course I have a beach trip to the panhandle of Florida planned this weekend!

Yep, and I leave here from home/Destin tomorrow for a family reunion Saturday and a camping getaway to St. Augustine and planned not to return till Monday. This might cause me a sooner than planned return trip to batten down if it looks to be coming toward the Destin area.

[Sanibel]

The ill-defined center is over land over Hispaniola.

[tolakram]

Sure enough, winds back to E after the storms moved on. http://www.wunderground.com/cgi-bin/wxS ... showrain=1

Sat loop: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=20

I'm waiting patiently for surface obs to start to indicate some kind of lower level circulation forming.