ATL : TROPICAL DEPRESSION ERIKA (06L)

[KWT]

Its not a strong ridge but the ECM does develop a ridge, its not much but there isn't really much in the way of troughing either post day-6.

The key is really how far west it can get, the weakness at upper level remains further east on the ECM whilst the GFS keeps it near the east coast for a lot longer before lifting it out.

Personally I think what we will see is this lift out to the NW, then bend back WNW before being lifted out totally around 70W when the high breaks down again, but we shall see!

[Sanibel]

I think we can interpolate Bill's intensification on to (soon to be) Erika here and assume intensification on the WNW track they are expecting.


When it gets a strong center we can look at GFDL.


Maybe Wxman57 can post one of those purple isobar black maps when it develops further to show the downrange steering regime.

[funster]

Traveling up the east coast but staying off shore seems to be the trend this year. Every year there seems to a path that two or more of the named storms end up following.

I say west of Bermuda but east of the U.S. east coast. Maybe an ULL will even show up and absorb it.

[curtadams]

I don't think there's a formal LLC yet. The quickscat showed the circ was very elongated and probably still part of the ITCZ to the west. I'm not seeing anything on RGB to make me think it's changed. I don't expect that to change until Dmax tonight, and then only if that shear doesn't interrupt.

I agree a threat from formation now is unlikely; in spite of the dangerous location the troughs are very likely to pull it N into a recurve. If it got into the Caribbean there's a threat but even the model that don't form a storm see enough of an effect from that S shear to send the wave N of the Antilles into a situation much like Danny.

[KWT]

I say west of Bermuda but east of the U.S. east coast.

I think thats the most likely track but we shall see, I think its early days yet though and I really wouldn't rule out anything till we get a better idea of the track in the next 12-24hrs.

[Sanibel]

Bad shear to the north but low over the disturbance itself. Moderate to unfavorable ahead:

[KWT]

Yeah though that shear is lifting out to some degree Sanibel and moving west faster then the disturbance itself.

[storms NC]

One other thing. Long-range projections (beyond 5 days) indicate a very weak high to its north once it passes the NE Caribbean. I don't see anything to drive it westward toward the East U.S. Coast. Could be a threat to Bermuda, or may even pass east of Bermuda.

I think it is way to early to predict for any where for the US. Just to far out and to low as of now to say past 3-5 days.IMO

[wxman57]

Maybe Wxman57 can post one of those purple isobar black maps when it develops further to show the downrange steering regime.

How about a yellow one? There's a significant weakness in the ridge to the north of the storm around 60W. That's why the models turn it sharply NW around then:

[wxman57]

One other thing. Long-range projections (beyond 5 days) indicate a very weak high to its north once it passes the NE Caribbean. I don't see anything to drive it westward toward the East U.S. Coast. Could be a threat to Bermuda, or may even pass east of Bermuda.

I think it is way to early to predict for any where for the US. Just to far out and to low as of now to say past 3-5 days.IMO

Not too early to predict at all, but it is too early to be confident in a prediction. Our clients demand to know impact probabilities from 10 days or more out. We don't deal with the general public, though.

Looking just a little ragged now on satellite. No update to best track database. Perhaps NHC is waiting until this afternoon to admit it's a TD?

[storms NC]

Had two to miss the EC and the 3rd time around could be the one that does hit the EC somewhere. That is what I have always heard. Old wives tail LOL.

[Derek Ortt]

the GFS winds? That model has been overdoing the northward motion big time.

While I agree with a miss of the EC, not a recurve at 58W. GFS seems hopelessly lost

[KWT]

Yeah the GFS really cannot be trusted at all with this one Wxman57, I wonder what the ECM would show.

Should be noted the GFS also brings out one more upper trough then the ECM and is far more keen on digging it down then the ECM, which barely shows it.

[wxman57]

the GFS winds? That model has been overdoing the northward motion big time.

While I agree with a miss of the EC, not a recurve at 58W. GFS seems hopelessly lost

Which would you like to see? I know, you like the ECMWF best. Sorry, don't get the high-res ECMWF data. Canadian global only goes out 5 days with the 400-700 mb wind field. Not really much else to use for 6-7 days out but GFS.

Here's the Canadian 500mb forecast (every 10m heights) for next Friday evening. Northward turn definitely indicated:

[Derek Ortt]

the GFS winds? That model has been overdoing the northward motion big time.

While I agree with a miss of the EC, not a recurve at 58W. GFS seems hopelessly lost

Which would you like to see? I know, you like the ECMWF best. Sorry, don't get the high-res ECMWF data. Canadian global only goes out 5 days with the 400-700 mb wind field. Not really much else to use for 6-7 days out but GFS.

Here's the Canadian 500mb forecast (every 10m heights) for next Friday evening. Northward turn definitely indicated:

seems a lot more reasonable. A turn between 65 and 70W. Do not see any threat to the United States (including PR/VI) at this time

[cycloneye]

Shear will be favorable according to the 12 UTC SHIP run.

Derek,what do think of the GFS vortex.

Code: Select all

                *   ATLANTIC SHIPS INTENSITY FORECAST       *
                    *      GOES DATA AVAILABLE                  *
                    *      OHC  DATA AVAILABLE                  *
                    *  INVEST      AL942009  08/30/09  12 UTC   *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    25    28    31    36    40    49    58    67    77    82    85    86    86
V (KT) LAND       25    28    31    36    40    49    58    67    77    82    85    86    86
V (KT) LGE mod    25    26    27    30    32    38    46    56    67    79    88    94    93

SHEAR (KT)        10     4     2     2     7     9    11     9     8     9     6    13     7
SHEAR DIR        320   354   145   355   321    13    35    83    46   120   165   199   251
SST (C)         28.0  27.8  27.6  27.5  27.4  27.7  27.9  28.2  28.4  28.5  28.6  28.7  28.7
POT. INT. (KT)   138   135   132   131   129   132   134   138   141   143   144   146   146
ADJ. POT. INT.   140   135   131   129   126   126   126   130   132   135   137   139   139
200 MB T (C)   -53.2 -52.6 -52.9 -53.2 -53.4 -53.4 -53.6 -53.4 -53.6 -53.5 -53.7 -53.7 -53.8
TH_E DEV (C)       9     9     9    10    10    11    11    11    11    12    11    12    11
700-500 MB RH     54    58    58    58    54    53    48    49    47    43    44    42    41
GFS VTEX (KT)     11    11    11    10    10     9     8     8    10    10     9     8     7
850 MB ENV VOR    57    45    38    20     5     0    -9     4    -4   -11   -15   -13   -26
200 MB DIV        31    47    50    29    22    39    14    19    27     9   -18   -29   -20
LAND (KM)       1020   987   971   975   982   993   874   768   671   607   587   479   283
LAT (DEG N)     11.8  12.4  12.9  13.5  14.0  14.8  15.2  15.4  15.5  15.7  16.0  16.3  16.7
LONG(DEG W)     46.3  47.5  48.7  49.8  50.9  52.8  54.3  55.7  57.1  58.5  60.0  61.7  63.6
STM SPEED (KT)    14    13    12    12    11     9     7     7     7     7     8     9     9
HEAT CONTENT      35    33    32    33    36    44    53    61    68    74    67    45    74

  FORECAST TRACK FROM BAMM      INITIAL HEADING/SPEED (DEG/KT):285/ 13      CX,CY: -12/  3
  T-12 MAX WIND:  25            PRESSURE OF STEERING LEVEL (MB):  600  (MEAN=624)
  GOES IR BRIGHTNESS TEMP. STD DEV.  50-200 KM RAD:  11.8 (MEAN=14.5)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD:  95.0 (MEAN=65.0)

                        INDIVIDUAL CONTRIBUTIONS TO INTENSITY CHANGE
                         6   12   18   24   36   48   60   72   84   96  108  120
                        ----------------------------------------------------------
  SAMPLE MEAN CHANGE     1.   2.   3.   4.   6.   8.   9.  11.  11.  12.  13.  13.
  SST POTENTIAL          0.   0.   1.   2.   5.  10.  16.  21.  25.  27.  29.  31.
  VERTICAL SHEAR MAG     1.   2.   4.   6.   8.  10.  11.  11.  11.  12.  12.  12.
  VERTICAL SHEAR DIR     0.   0.   1.   1.   2.   4.   6.   9.  10.  10.   8.   6.
  PERSISTENCE            0.  -1.  -1.  -1.  -1.  -1.  -1.  -1.  -1.   0.   0.   0.
  200/250 MB TEMP.       0.   0.   0.   0.  -1.   0.   0.   0.   0.   0.   1.   1.
  THETA_E EXCESS         0.   0.   0.   0.   0.  -1.   0.  -1.   0.   0.   0.   0.
  700-500 MB RH          0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GFS VORTEX TENDENCY    0.   0.  -1.  -1.  -2.  -3.  -4.  -2.  -3.  -4.  -4.  -5.
  850 MB ENV VORTICITY   0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -2.  -2.  -2.
  200 MB DIVERGENCE      0.   0.   0.   1.   1.   1.   1.   1.   1.   0.  -1.  -1.
  ZONAL STORM MOTION     0.   0.   1.   1.   2.   2.   3.   3.   3.   4.   4.   4.
  STEERING LEVEL PRES    0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  DAYS FROM CLIM. PEAK   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GOES PREDICTORS        1.   2.   3.   4.   4.   4.   3.   2.   1.   1.   1.   1.
  OCEAN HEAT CONTENT     0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -1.   0.   0.
                        ----------------------------------------------------------
  TOTAL CHANGE           3.   6.  11.  15.  24.  33.  42.  52.  57.  60.  61.  61.

   ** 2009 ATLANTIC RI INDEX AL942009 INVEST     08/30/09  12 UTC **
           ( 30 KT OR MORE MAX WIND INCREASE IN NEXT 24 HR)
 
 12 HR PERSISTENCE (KT):   0.0 Range:-45.0 to  30.0 Scaled/Wgted Val:  0.6/  1.3
 850-200 MB SHEAR (KT) :   4.9 Range: 26.2 to   3.2 Scaled/Wgted Val:  0.9/  1.2
 D200 (10**7s-1)       :  35.8 Range:-21.0 to 140.0 Scaled/Wgted Val:  0.4/  0.5
 POT = MPI-VMAX (KT)   : 107.3 Range: 33.5 to 126.5 Scaled/Wgted Val:  0.8/  0.5
 850-700 MB REL HUM (%):  68.0 Range: 56.0 to  85.0 Scaled/Wgted Val:  0.4/  0.3
 % area w/pixels <-30 C:  90.0 Range: 16.0 to 100.0 Scaled/Wgted Val:  0.9/  0.2
 STD DEV OF IR BR TEMP :  11.8 Range: 30.6 to   3.2 Scaled/Wgted Val:  0.7/  1.1
 Heat content (KJ/cm2) :  33.8 Range:  0.0 to 130.0 Scaled/Wgted Val:  0.3/  0.0
 
 Prob of RI for 25 kt RI threshold=    41% is   3.3 times the sample mean(12.3%)
 Prob of RI for 30 kt RI threshold=    24% is   3.0 times the sample mean( 8.0%)
 Prob of RI for 35 kt RI threshold=    16% is   3.3 times the sample mean( 4.8%)

   ##         ANNULAR HURRICANE INDEX (AHI) AL942009 INVEST     08/30/09  12 UTC         ##
   ## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=5 NFAIL=2                          ##
   ## AHI=  0   (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
   ##     ANNULAR INDEX RAN NORMALLY           

[Derek Ortt]

you know what I think of the GFS in general. Good For S***

[cycloneye]

Ok lets stop here.

[gatorcane]

starting to look ragged again, looks closer to a strong tropical wave. That will let it keep going more west as long as it doesn't deepen that quickly. Not so sure of a recurve 65-70W. Seems possible but still too early too call.

[wxman57]

With the convection decreasing now, I can see the lower-level spin south of 12N not north of 12N.