OrlandoDan
Storm Tracker
Reged: Mon
Posts: 256
Loc: Longwood, FL 28.69N 81.44W
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Looking at the sats this morning, it is apparent the main area of convection dipped a bit south over the night hours. I wonder what effect this will have on the upcoming update from the and the models.
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Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008)
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OrlandoDan
Storm Tracker
Reged: Mon
Posts: 256
Loc: Longwood, FL 28.69N 81.44W
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Erika is definitely a challenge for the models to get a grip on. Sure enough, there was a southward shift over the night hours:
000
WTNT41 KNHC 020859
TCDAT1
TROPICAL STORM ERIKA DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062009
500 AM AST WED SEP 02 2009
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS BEEN SEARCHING
FOR THE CENTER OF THE TROPICAL STORM OVER THE PAST FEW HOURS. THE
CIRCULATION HAS BECOME QUITE DISORGANIZED...BUT IT APPEARS THAT THE
CENTER HAS REFORMED TO THE SOUTHWEST OF THE PREVIOUSLY ESTIMATED
TRACK. HOWEVER THE FLIGHT-LEVEL WINDS SUGGEST THAT THERE MAY BE
MULTIPLE CENTERS...SO THE ADVISORY POSITION IS HIGHLY UNCERTAIN AND
PROBABLY REPRESENTS A MEAN CENTER...OR THE LOCATION OF THE
LOW-LEVEL VORTICITY MAXIMUM. THE INITIAL MOTION...270/4...IS OF
COURSE ALSO HIGHLY UNCERTAIN. TO MAINTAIN SOME CONTINUITY FROM THE
PREVIOUS FORECAST AND FOLLOWING THE TRACK GUIDANCE...A WEST-
NORTHWESTWARD TRACK IS PREDICTED TO RESUME. ERIKA SHOULD BE
STEERED BY THE FLOW TO THE SOUTH OF A WEAK SUBTROPICAL RIDGE FOR A
COUPLE OF DAYS. LATER IN THE FORECAST PERIOD...DYNAMICAL GUIDANCE
SHOWS A MORE NORTHWESTWARD MOTION FOR A STRONGER CYCLONE...E.G. THE
GFDL AND HWRF...AND A CONTINUED WEST-NORTHWESTWARD MOTION FOR A
WEAKER SYSTEM...E.G. THE . THIS IS A LOW-CONFIDENCE TRACK
FORECAST.
DATA FROM THE AIRCRAFT INDICATE THAT ERIKA HAS WEAKENED A LITTLE...
WHICH IS NOT SURPRISING CONSIDERING THE DISORGANIZED APPEARANCE OF
THE SYSTEM ON SATELLITE IMAGES. MODERATE WESTERLY SHEAR HAS BEEN
DISRUPTING THE CYCLONE BUT THE SHEAR IS NOT EXPECTED TO BE STRONG
ENOUGH TO PREVENT SOME STRENGTHENING DURING THE NEXT DAY OR SO.
THEREAFTER...AN UPPER-TROPOSPHERIC TROUGH FARTHER TO THE WEST IS
LIKELY TO IMPART INCREASING SOUTHWESTERLY SHEAR ON ERIKA...WHICH
SHOULD INDUCE WEAKENING. THE INTENSITY FORECAST IS VERY
SIMILAR TO THE PREVIOUS OFFICIAL FORECASTS...BUT BELOW THE
CONSENSUS OF THE NUMERICAL INTENSITY GUIDANCE. IT SHOULD BE NOTED
THAT SOME OF THESE NUMERICAL MODELS...SUCH AS THE HWRF AND ...
HAVE SHOWN A HIGH BIAS FOR A COUPLE OF THIS YEAR'S ATLANTIC
TROPICAL CYCLONES.
GIVEN THE SOUTHWARD SHIFT IN THE TRACK...A TROPICAL STORM WARNING
HAS BEEN ISSUED FOR THE NORTHERN LEEWARD ISLANDS.
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Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008)
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Evan Johnson
Weather Guru
Reged: Fri
Posts: 143
Loc: Loxahatchee, FL 26.79N 80.28W
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uhh, is it me or has this storm jogged a bit to the south? id continue to watch those models, they will shift more to the west. as it is, they dont have a grasp on what this thing is doing. half are to the north half are to the south. we just have to watch it. its lost some steam, but conditions are favorable to beef itself up within the next 24 hours.
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MikeC
Admin
Reged: Sun
Posts: 2798
Loc: Orlando, FL 28.49N 81.47W
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Parts of Erika are starting to come into range of the Martinique Radar. Erika as a whole is reminding me a whole lot of Chris from 3 years ago which had center vs convection issues and had a convection/center "split off" after it got past the Leewards.
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OrlandoDan
Storm Tracker
Reged: Mon
Posts: 256
Loc: Longwood, FL 28.69N 81.44W
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Notice the burst of convection right at 16.5N 59W. That is just south of the Tropical Forecast point.
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Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008)
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Hawkeyewx
Weather Analyst
Reged: Sun
Posts: 53
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Erika's organization is pretty messy this morning. There is a notable surface spin over Guadeloupe, moving southwest, but that may be the original central vortex from last night that rotated back out from under the convection. Recon got a center fix an hour ago well east of Guadeloupe. New convection is firing even farther east. What we possibly have is a mean center with little vorts rotating around it.
It's interesting that Erika will now likely track over the northern Leeward islands.
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berrywr
Weather Analyst
Reged: Fri
Posts: 344
Loc: Opelika, AL 32.71N 85.23W
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I'm looking at Martinque radar and you can see at least one center crossing the islands as we speak and it is clearly detached from the mid level circulation. Satellite imagery is also indicating their detached. I've just began to look at all of this but wanted to post a brief blip about what looks like an impressive image on satellite and once again close examination of the lower levels of the system.
I requested my username to be changed from alaberrypatch to berrywr; we are one and the same.
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Sincerely,
Bill Berry
"To work in the service of life and the living..." - John Denver
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OrlandoDan
Storm Tracker
Reged: Mon
Posts: 256
Loc: Longwood, FL 28.69N 81.44W
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IR RGB gives a pretty good picture of where the LLC (at least one of them) is right now. It also gives a good 3D perspective on the lower level vs mid and upper levels.
http://www.ssd.noaa.gov/goes/flt/t2/loop-rgb.html
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Keith (1988), Charley (2004), Frances (2004) , Jeanne (2004), Fay (2008)
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Lamar-Plant City
Storm Tracker
Reged: Mon
Posts: 232
Loc: Plant City, Florida 28.01N 82.12W
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Is the 'relocation' toward the south actual movement or is it just the part of a center 'wobble' that moves south, then later in the rotation will spin around and it will look like the center is moving more toward the north? These weak systems do tend to wobble like a slow spinning top. Don't be tricked by a wobbly LLC into thinking it is a movement trend.
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If you don't like the weather, wait 5 minutes...
2013 Season Prediction: 18/9/4
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berrywr
Weather Analyst
Reged: Fri
Posts: 344
Loc: Opelika, AL 32.71N 85.23W
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02/14Z - Morning everybody! - Good news and bad news! Good news, sattelite and radar imagery out of Martinque confirms at least one LLC detached from convection to the east. A closer look at IR imagery just before visible imagery clearly shows the system is being adversely effected by shear to its west and today to its north. Wind Shear analysis out of SSEC confirms shear to its north is stronger today, but weaker to the west, but sufficient to impose problems currently over the system.
The bad news: Erica remaining shallow is going to favor a more west forecasted course and slower moving system as upper features change with the ridge to the north and northeast of the system extending a ridge axis westward and interesting enough a cutoff low progged to be in the Midwest-South Central US with just enough of a trough extending into the GOM and an upper ridge over the western Carribbean extending southwestward towards South America.
Erika is embedded in what is referred to as col; a neutral region between two (surface and/or upper) lows and highs. Very weak steering currents are the norm.
The appearance of convection for the past two mornings have been very impressive on satellite and once again the common denominator is where convection exists, very low shear aloft.
Aircraft vortex data revealed at 1143Z winds were 24 knots at 850 mbs, extrapolated SLP of 1008 mbs (up 4 mbs) and Max FL winds were 33 knots in the NE quadrant.
The 1242Z Quikscat indicated winds near 50 knots in convection well to the east of the LLC but rain-corrupted measurements were the norm, but there were some good numbers measured.
I'm not as confident as I was yesterday about the future track of Erika. Shear forecasted over the next two to three days near the US is extremely hostile, but Erika is not expected to move much over the next several days and upper features will change.
I'm not going to speculate where Erika will go with the variables in play and nor is it clear whether Erika can remain a viable tropical cyclone, but we can speculate!
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Sincerely,
Bill Berry
"To work in the service of life and the living..." - John Denver
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hogrunr
Weather Guru
Reged: Sun
Posts: 153
Loc: Spring, TX 30.07N 95.51W
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TROPICAL STORM ERIKA DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062009
1100 AM AST WED SEP 02 2009
VISIBLE SATELLITE IMAGES AND AIR FORCE RESERVE HURRICANE HUNTER
DATA SHOW THAT ERIKA IS A POORLY ORGANIZED SYSTEM. THERE ARE
MULTIPLE SWIRLS APPARENT ON THE SATELLITE IMAGERY ROTATING IN THE
LARGER CIRCULATION ENVELOPE WITH A MEAN CENTER TO THE WEST OF THE
DEEP CONVECTION. THE SFMR EARLIER REPORTED WINDS OF ABOUT 35
KT...WHICH IS IN GOOD AGREEMENT WITH SATELLITE INTENSITY
ESTIMATES...SO THAT VALUE WILL BE USED AS THE INITIAL INTENSITY.
.....DESPITE ALL THIS
SHEAR...ALL RELIABLE GUIDANCE RESTRENGTHENS THIS SYSTEM TO NEAR
HURRICANE STRENGTH IN A FEW DAYS. THIS REINTENSIFICATION
DOES NOT SEEM VERY LIKELY AND THE FORECAST IS MUCH LOWER THAN
THE GUIDANCE. GIVEN THE POSSIBLE SHEAR DURING THE FORECAST
PERIOD...IT WOULD NOT BE SURPRISING IF ERIKA DISSIPATED.
....THE OFFICIAL FORECAST HAS BEEN
SHIFTED LEFT OF THE PREVIOUS ONE AND IS LEFT OF THE DYNAMICAL
CONSENSUS DUE TO THE ANTICIPATION OF ERIKA REMAINING WEAK. IT
SHOULD BE EMPHASIZED THAT...OVERALL...THIS IS A LOW-CONFIDENCE
TRACK FORECAST.
The forecast is about as erratic as Erika at this point...hard for anyone to tell.
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MikeC
Admin
Reged: Sun
Posts: 2798
Loc: Orlando, FL 28.49N 81.47W
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The 2006 Chris like scenario, where it makes it a bit further west and basically falls apart, especially if there is land interaction seems likely for Erika. Future track places it in the Bahamas, but it likely won't be much when it gets there.
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hogrunr
Weather Guru
Reged: Sun
Posts: 153
Loc: Spring, TX 30.07N 95.51W
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It seems weird that basically all of the intensity models would miss that drastically on this one. As the said, it is basically going against all model guidance for intensity by calling for this system to dissipate! But they also said it was fairly low confidence also...
Wunderground Intensity Plot
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berrywr
Weather Analyst
Reged: Fri
Posts: 344
Loc: Opelika, AL 32.71N 85.23W
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Refer to SSEC Wind Shear Analysis, Navy Wind Shear Forecasts and Models and Forecast Branch 300mb and 200mb Analysis:
SSEC Wind Shear: http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8shr.html
Navy Wind Shear Forecast: http://www.nlmoc.navy.mil/cgi-bin/wxgrid.pl?aor+ngpshrcolor+aor+ngpshr+aor+avnshr
NCEP 200mb at 02/12Z: http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_200_000l.gif
NCEP 300mb at 02/12Z: http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_300_000l.gif
NWSFO San Juan Model Guidance Page: http://www.srh.noaa.gov/sju/?n=model01
Courtesy of 15Z Discussion:
VERTICAL WIND SHEAR HAS INCREASED EARLIER THAN EXPECTED...WITH CIMSS
DIAGNOSING ABOUT 15-20 KT OF SHEAR. AT FIRST GLANCE...THE SHEAR DOES
NOT APPEAR TO BE TOO STRONG OVER THE SYSTEM WITH SOUTH OR
SOUTHEASTERLY WINDS REPORTED AT 200 MB OVER THE NORTHERN LEEWARD
ISLANDS. HOWEVER...UPPER-AIR DATA FROM GUADELOUPE AND ST. MAARTEN
SUGGEST THAT THE SHEAR IS PRIMARILY COMING FROM SOUTHWESTERLY WINDS
BETWEEN 300 MB-250 MB...AND THIS IS APPARENTLY UNDERCUTTING THE
OUTFLOW LAYERS AT 200 MB AND ABOVE. MOST OF THE GLOBAL MODELS DO
NOT SHOW MUCH RELAXATION OF THIS SHEAR...AND ACTUALLY SHOW IT
INCREASING SIGNIFICANTLY IN A COUPLE OF DAYS. DESPITE ALL THIS
SHEAR...ALL RELIABLE GUIDANCE RESTRENGTHENS THIS SYSTEM TO NEAR
HURRICANE STRENGTH IN A FEW DAYS. THIS REINTENSIFICATION
DOES NOT SEEM VERY LIKELY AND THE FORECAST IS MUCH LOWER THAN
THE GUIDANCE. GIVEN THE POSSIBLE SHEAR DURING THE FORECAST
PERIOD...IT WOULD NOT BE SURPRISING IF ERIKA DISSIPATED."
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Sincerely,
Bill Berry
"To work in the service of life and the living..." - John Denver
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Lamar-Plant City
Storm Tracker
Reged: Mon
Posts: 232
Loc: Plant City, Florida 28.01N 82.12W
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This storm REALLY looks like it is separating (or decoupling) the convection from the centers of circulation. On visible, it looks like the convection is stationary while the LLC continues to move off to the WSW. The tops of the latest convective burst even look as if they might be blowing off to the SE. What is going on with this system? If it keeps this up, I could easily see it dissipating or at least going back to an open wave until the shear relaxes or it moves into a lower sheer environment.
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If you don't like the weather, wait 5 minutes...
2013 Season Prediction: 18/9/4
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weathernet
Storm Tracker
Reged: Sat
Posts: 296
Loc: Elsewhere 80.30N 50.63E
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Interestingly the various models are often slow to pick up some tropical systems, and yet they can be equally slow to "let go" or weaken a system. Given the current appearance, along with the newer data suggesting a less obvious lower level ( 300mb ) shear at play, and then potentially add in a possible factor of interaction with land ( Puerto Rico perhaps ), one would have to re-think the near term health of this particular tropical system. I for one, fully anticipated continued strengthening based on looking at more simplified single level 200mb charts and Erica's projected motion. I will say this however, "if" a relativly healthy mid level is maintained, and without getting fully dragged over most of the Greater Antilles, and somehow maintains some convective identity while slowly moving more or less WNW over time, it would be extremely prudent for those in the Bahamas and Florida to remain keenly aware that given the right conditions, tropical systems can develop fairly quickly.
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danielw
Moderator
Reged: Wed
Posts: 3406
Loc: Hattiesburg,MS (31.3N 89.3W)
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Hour old visible...roughly
You can visualize some of the levels of shear mentioned by in Berry's post above.
Large image here:
http://i.flhurricane.com/images/2009/GOES15452009245u8WRNv.jpg
Vis, IR and WV imagery available here:
http://weather.msfc.nasa.gov/GOES/goeseasthurr.html
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Robert
Storm Tracker
Reged: Sat
Posts: 258
Loc: Southeast, FL
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Ericka just seems elongated like abroad trough of low pressure moving wnw across the upper antillies. with a small vorticy, pingponging around a much broader one.
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MikeC
Admin
Reged: Sun
Posts: 2798
Loc: Orlando, FL 28.49N 81.47W
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The latest keeps it going west, then over the islands into the southern Bahamas later, canadian moves it due west and dissipates it.
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MikeC
Admin
Reged: Sun
Posts: 2798
Loc: Orlando, FL 28.49N 81.47W
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There are more indications now that a Chris/2006 type scenario is unfolding, where the LLC is racing away from the convection, which, most likely, will keep Erika moving west and it is more likely to fall apart then to do much more. We'll see how it does overnight.
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