Surface Trough East of Florida (Is Invest 90L)

[TheStormExpert]

Wind Shear is going to have to decrease a GOOD DEAL in order to allow any type of development to occur. Currently there is about 40-50kts. of wind shear over the area of interest and it looks to only be decreasing 10kts. which is not enough.

[Riptide]

It is one of those post-frontal TCs, wind shear is good in the developmental phase.

[NDG]

TV Mets in my area need to stop calling this a current "tropical" disturbance, this disturbance is currently non-tropical, there is a potential of it gaining subtropical and or eventually tropical characteristics over the next few days if enough latent heat from convection occurs close to the low pressure area.

[TropicalAnalystwx13]

Wind Shear is going to have to decrease a GOOD DEAL in order to allow any type of development to occur. Currently there is about 40-50kts. of wind shear over the area of interest and it looks to only be decreasing 10kts. which is not enough.

And that is what is currently forecast to occur. As the negatively-tilted upper-level trough pinches off into an upper-level low, the disturbance should find lighter shear underneath the low. As Levi hinted at in his update, the upper-level setup should provide a nice poleward outflow channel that helps lower central pressures. Couple that with its slow movement over the abnormally warm waters of the Gulf Stream, and it would not surprise me to see a moderate fully tropical storm as this thing reaches its peak.

[RL3AO]

Wind Shear is going to have to decrease a GOOD DEAL in order to allow any type of development to occur. Currently there is about 40-50kts. of wind shear over the area of interest and it looks to only be decreasing 10kts. which is not enough.

[img]http://i58.tinypic.com/2ugzcjc.gif[ /img]

[img]http://i62.tinypic.com/330wvp5.gif[ /img]

Just because there is a lot of shear now doesn't mean there will be a lot of shear in 4 to 5 days. The current shear is caused by a fairly impressive upper level trough which will help develop the non-tropical low near the Bahamas.



However, in four days the models leave a cutoff upper level low with much weaker steering winds. This may allow the system to meander near the Gulf Stream and slowly develop sub-tropical characteristics.

[AJC3]

Let's remember not to be myopic about the "tropical" component of development, especially this early in the game. That phase, when and if it occurs to any significant extent, isn't forecast to start until later in the week.

The initial phase of development of this low is purely baroclinic - 100 percent dynamically forced pressure falls. Rather than diagnosing upper tropospheric shear, it would be much, much more productive to look at the primary contribution(s) to upward vertical motion/rising air. Analysis and forecasts of 250 MB divergence will show the location of the areas of strongest jet forced ascent. Looking of 3-hourly SLP changes will show the areas of greatest sea level pressure falls resulting from this ascent.

Currently, forced ascent is strong and occurring over a large area. Expect this to continue with a broad inverted surface trough gradually amplifying over the next 1-2 days, followed by formation of what should be a broad, baggy surface low, possibly containing one or more embedded smaller scale lows or vortices.

"Follow the rising air"

For starters...

UCAR surface plot (user can select area to display, parameters and density of METARs, etc.)
http://weather.rap.ucar.edu/surface/jav ... size=large

CIMSS 250MB divergence
http://tinyurl.com/4xnotar

HRRR forecast 3-hourly SLP falls...
http://tinyurl.com/m2lxkdx

With a little searching, you should be able to find analyses and model output for these and other parameters such as 700MB vertical velocity, etc.

Some folks are making some excellent posts toward this end - some of our less-learned peeps would do well to closely read their posts.

[tropicwatch]

Well if the windshear is forecast to diminish during the next couple of days, there is potential. Currently there does not appear to be anything to move these disturbed areas before that time.

[NDG]

SE Coastal FL is getting the rain that many thought were not going to get out of the system.

[NDG]

Today's 12z models should get a better grip on this system today, hopefully, the vorticity near Andros Island seems to be the one taking over as it slowly moves northward.

[gatorcane]

ECMWF still liking this system, it will be gradual process but still think there is a chance at a named system out of this:

[Steve]

Well if the windshear is forecast to diminish during the next couple of days, there is potential. Currently there does not appear to be anything to move these disturbed areas before that time.

I think you need shear to get this going anyway with a pattern reversal with the disturbance up against the upper trough. The eddy to the SE would be the point of spin. We almost always see something like that with in-close development of existing disturbed weather in June and October/November. That's the nature of the beast at the beginning and end of the season. Looks like the 06GFS wants a big rainmaker for SC/GA/NC as it traps the remnant low. Low-res ECMWF keeps it much weaker and takes it up and out quickly. I don't have access to the parallel or high res solutions, so I don't know what its real outputs show. NAM 06Z simulated radar spins up a "tropical storm looking structure" that gives the look of something tightening at landfall in southern South Carolina. Only way that happens if the ridge over the top builds in over the system (sort of like what the GFS has progged). Ordinarily you'd want to dismiss that solution in May because you'd want to assume most systems would blow out ENE or NE pretty quickly. But with the warm water off the North Atlantic Coast, you could see the legitimacy of a ridge building back.

Tough call either way though if it strengthens as the 06 GFS has it, 24 hours you have a low popping in the Northern Bahamas. At 48, you have closed isobars east of the FL/GA border. At 72 hours, you have a tightening system (TS? STS?) approaching the low country/southern South Carolina coast. And at 96, it's moving back down a bit being pressed down by the ridge building in over top and down from Quebec. 500mb vorticity shows it nicely
http://moe.met.fsu.edu/cgi-bin/gfstc2.c ... =Animation

850 over 200 shear run as well.

No call either way, but the ECMWF (public) and GFS have opposite solutions at this point. We'll know in 3 days which one had it right.

[tolakram]

live visible: http://wwwghcc.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=26&lon=-78&info=vis&zoom=2&width=1000&height=800&quality=92&type=Animation&palette=ir1.pal&numframes=10&mapcolor=gray

[NDG]

Atlantic Tropical Weather Outlook


000
ABNT20 KNHC 051359
TWOAT

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
1000 AM EDT TUE MAY 5 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

A large area of disorganized showers and thunderstorms extending
from the northwestern Caribbean Sea across Cuba, southern Florida,
and the Bahamas is associated with an upper-level trough and a weak
surface trough. An area of low pressure is expected to form in
association with this disturbance during the next day or two. The
low could gradually acquire subtropical characteristics over the
next few days while it moves generally northward at a slow forward
speed. For additional information on this system, see High Seas
Forecasts issued by the National Weather Service. The next Special
Tropical Weather Outlook will be issued on this system by 11 AM EDT
Wednesday.
* Formation chance through 48 hours...low...20 percent
* Formation chance through 5 days...medium...40 percent

&&

High Seas Forecasts issued by the National Weather Service are
available under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and
on the Web at http://www.opc.ncep.noaa.gov/shtml/NFDHSFAT1.shtml.

$$
Forecaster Brennan

[northjaxpro]

This system will be an extremely slow moving, meanderer and I am beginning to side with the GFS developing this hybrid/potential sub-tropical system within 100-150 miles off the Florida East Coast. High surf, rip currents and potential beach erosion are definite possibilities along the SE U.S. ATL coastline, along with some decent rainfall by the latter portions of this week into the weekend, especially for the GA/SC and potential NC coastal regions. The large High Pressure area off the Northeast US is suppose to strengthen as it builds down the U.S. East Coast this weekend, which leads to the thinking that will tug this system westward or posibly southwestward, depending on the strength of the building ridge, toward the coast or possibly making landfall during the weekend. Definitely an intersting situation for all interests along the SE U.S. Coast the rest of this week.

___________
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster. For official information, please refer to the NHC and NWS products.[td10

.

[wxman57]

Shear shouldn't be a major impediment to subtropical development. Nothing to indicate a strong storm, though. Top winds 30-40 kts, perhaps. Main threat would be rainfall if it moves into the coast.

[NDG]

some beach erosion could be a problem also.

[Hypercane_Kyle]

I expect our AOI to be tagged 90L today. I don't see much indication that a surface low is forming right now, although I admit to not looking very hard.

[Hurricaneman]

I expect our AOI to be tagged 90L today. I don't see much indication that a surface low is forming right now, although I admit to not looking very hard.

http://i.imgur.com/qz0zoW4.gif

Id look just west of Andros Island as that seems to be where I see a diffuse low

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[cycloneye]

Invest 90L should be tagged later this afternoon or tonight as the squadron gets ready to investigate on Wednesday morning..

REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1115 AM EDT TUE 05 MAY 2015
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 06/1100Z TO 07/1100Z MAY 2015
TCPOD NUMBER.....15-002

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (NORTH OF NORTHWESTERN BAHAMAS)
FLIGHT ONE -- TEAL 71
A. 06/1800Z
B. AFXXX 01AAA INVEST
C. 06/1500Z
D. 30.0N 76.0W
E. 06/1745Z TO 06/2215Z
F. SFC TO 10,000 FT

FLIGHT TWO -- TEAL 72
A. 07/1130Z
B. AFXXX 0201A CYCLONE
C. 07/0800Z
D. 31.0N 75.0W
E. 07/1115Z TO 07/1500Z
F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY: CONTINUE 12-HRLY FIXES IF SYSTEM
DEVELOPS AND REMAINS A THREAT.

[NDG]

I expect our AOI to be tagged 90L today. I don't see much indication that a surface low is forming right now, although I admit to not looking very hard.

http://i.imgur.com/qz0zoW4.gif

Id look just west of Andros Island as that seems to be where I see a diffuse low

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Yes, that's the area to keep an eye on, and as expected the 12z NAM and 12z GFS (so far) show that vorticity taking over and developing.