ATL: ISAAC - Post-Tropical - Discussion

[Gustywind]

8 PM TWD



000
AXNT20 KNHC 172355 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI AUG 17 2012

CORRECTED FOR LATEST INFORMATION ON GORDON

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 11N24W TO 17N21W MOVING W AT 15-20
KT. THE WAVE IS EMBEDDED WITHIN AN EASTERN ATLC MONSOON GYRE
FOCUSED AROUND A 1009 MB LOW CENTERED NEAR 11N24W. TOTAL
PRECIPITABLE WATER IMAGERY INDICATES DEEP LAYER MOISTURE IN THE
VICINITY OF THE WAVE FROM 08N-15N BETWEEN 18W-24W WITH ISOLATED
MODERATE CONVECTION OCCURRING WITHIN 180 NM EITHER SIDE OF THE
WAVE AXIS.

[Aric Dunn]

exactly the convection has weakened today as developing systems typically do. tonight will help us figure things out.

These are the times I really miss QUIK-SCAT. I mean, ASCAT is nice, but not quite what we once had.

yeah its sad the funding fell through for a replacement maybe I should take up the challenge and develop a new sensor to replace it.

[SoupBone]

Does anyone have the link to the mid-level SAL? Someone was explaining its interaction with storms as compared to upper level SAL that most of us watch. My computer crashed and I lost the link.

[cycloneye]

Aric,I posted earlier an image with some new popcorn type clouds. Now there is a little bit more than 2 hours ago.

[Aric Dunn]

Aric,I posted earlier an image with some new popcorn type clouds. Now there is a little bit more than 2 hours ago.

yeah I have been watching. the mid level circ is very vigorous some deep convection would help consolidate things. the moisture envelope is very sufficient and can support - 70 to 80 degree tops. just have to see how the low level convergence is. if last night was an indication of anything than we will probably see it happen again tonight.

[floridasun78]

it look rain could get rain leewards few days ahead their at storms ahead of main 94l

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[cycloneye]

I think this will help 94L to start to consolidate down the road. The 00z TAFB surface analysis dissipates low in front of 94L.

[invest man]

how will a weakening Helene effect any weaknesses along the east coast or will there be no weakness and allow this system to keep trucking westward?

[gatorcane]

For all you mobile users, here is a loop of the system though it is 6 hours behind:

http://www.nhc.noaa.gov/mobile/sat_zoom ... _loop.html

The structure looks great and the system is in a low shear environment so the cloud pattern is very symmetric and is showing a "fanning," spiral-looking appearance. Convection will eventually build. Should be code orange by tomorrow.

[floridasun78]

this Isaac ? http://en.wikipedia.org/wiki/File:Isaac_2006_track.png that was fish storm

[cycloneye]

The 850mb vorticity is slowly increasing.

[Aric Dunn]

The 850mb vorticity is slowly increasing.

notice 94l has more voricity than helene... those maps are useful to an extent.

[Aric Dunn]

wow 00z gfs way south .. actually has a south of west motion... big shift.

[KWT]

Yep similar to the 18z GFS run Aric, suggests a major threat to the E.Caribbean...

[jinftl]

Up to Code Orange at 2am:

NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SAT AUG 18 2012

SHOWERS AND THUNDERSTORMS HAVE BECOME MORE CONCENTRATED IN
ASSOCIATION WITH A TROPICAL WAVE LOCATED A COUPLE OF HUNDRED MILES
SOUTHWEST OF THE CAPE VERDE ISLANDS. SLOW DEVELOPMENT OF THIS WAVE
IS POSSIBLE DURING THE NEXT FEW DAYS AS IT MOVES TOWARD THE WEST AT
15 TO 20 MPH. THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

[KWT]

30%, slowly increasing percentages happening, still think tomorrow may not be a bad call for development.

[HurricaneMaster_PR]

SSD classification up to 1.0/1.0

DATE/TIME LAT LON CLASSIFICATION STORM
18/0600 UTC 12.2N 26.7W T1.0/1.0 94L
17/2345 UTC 11.5N 25.2W TOO WEAK 94L

[meriland23]

So I noticed on NHC that this is slowly increasing in percentag and that it is quite far south, south of the cape verde, which from what I understand, is where the threatening systems hail from, south. I am wondering what info you guys have, is this predicted to become anything? And if so, a possible threat to the US? I know it is far out, but just so far.

[AJC3]

So I noticed on NHC that this is slowly increasing in percentag and that it is quite far south, south of the cape verde, which from what I understand, is where the threatening systems hail from, south. I am wondering what info you guys have, is this predicted to become anything? And if so, a possible threat to the US? I know it is far out, but just so far.

I would read back a few pages. It's much too early to speculate on a sepcific threat to the U.S. Sure, it's possible, however so is a recurve, and so is a track straight through the Caribbean. The initial guidance runs showed a turn to the NW just east of the Lesser Antilles, however the last few runs have trended much father south and west, indicating a threat there.

As far as what this disturbance will become, I would look at the model thread. There's some pretty big disparity between the ECM and GFS operational runs.

My advice is to just look at the general track and intensity trends within the whole suite of operational and ensemble runs of the model guidance over the next several days, rather than get too concerned about specifics.

[cycloneye]

This is from the San Juan NWS discussion of this morning.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
506 AM AST SAT AUG 18 2012


THE ELEPHANT IN THE KITCHEN...SO TO SPEAK...IS THE GFS FORECAST OF A
HURRICANE PASSING BETWEEN CULEBRA AND SAINT THOMAS LATE SATURDAY.
THIS CAUSES NORTHEAST FLOW AT THE SURFACE TO BEGIN THURSDAY AND
STRENGTHEN FRIDAY AND SATURDAY. ENSEMBLE SOLUTIONS SHOW A WIDE
RANGE OF TRACKS AND THE GFS LIKELY HAS NOT STABILIZED SUFFICIENTLY.
THE GFS TRACK SOLUTION WAS WELL TO THE NORTHEAST OF THE ISLANDS 24
HOURS AGO AND THE 18Z RUN SHOWED THE STORM PASSING TO THE SOUTH A
LITTLE EARLIER...BUT AM UNABLE TO LOAD MOST OF THE PARAMETERS FROM
THIS...18/00Z...MODEL FORECAST PACKAGE DUE TO THE UNCERTAINTY YET IN THE
FORECAST AND THE SEVERITY OF THE CONDITIONS FORECAST...EVEN FOR A
SYNOPTIC SCALE MODEL. SOME CHANGE TO THE TRACK IS LIKELY AND IT IS
IMPOSSIBLE TO TELL IF THIS WOULD TAKE THE CYCLONE NORTH OR SOUTH
OF THE AREA...ALTHOUGH FORMATION IN THE NEXT 72 HOURS SEEMS MORE
LIKELY THAN IT WAS YESTERDAY. THEREFORE WILL SIMPLY SAY THAT THIS
SOLUTION IS PLAUSIBLE AND PRELIMINARY SEASONAL PREPARATIONS SHOULD
BE COMPLETED AND DOUBLE CHECKED...BUT NO CONFIDENCE CAN BE GIVEN
TO THE CLOSE-PASSAGE SCENARIO YET.