ATL: GRACE - Models

[gatorcane]

the biggest difference is it develops the wave behind Grace. The 12Z showed no such development. Could be focusing more energy with that wave

I looked at that wave currently over Africa the GFS is developing and it doesn't look that impressive. Could easily see it drop it in the next run. Might be some convective feedback issues we have seen this season with the GFS on waves exiting Africa.

[CaliforniaResident]

I am going to go out on a limb and say Grace might far exceed the models in strength; does anyone think this will become a major at one point? Maybe even a cat 4 or 5 if the sheer relaxes down to null when it reaches that "sweet spot"?

[LarryWx]

Interestingly enough, the 12Z Sat Crazy Uncle (CMC) dropped the idea of Grace being an intact TC approaching the Bahamas. This is the first run to do so since the 12Z Thu run.

[LarryWx]

Per the 0Z GFS, Grace slowly gets stronger through Tue while shear is under 10 knots, but then it weakens when shear rises to the 10-15 knots range (which doesn't really seem all that high) while approaching 50W.

Edit: This is headed toward the Leewards/VI/PR as a weak TC.
Look at the bright side. People like Luis on PR could benefit from a weak but wet Grace.

Edit: As it reaches the Leewards, shear increases to near 20-25 knots, which is consistent with earlier GFS runs. Thus Grace further weakens.
Beneficial rains into the VI's and PR. Yay if this were to end up verifying!

This run is a bit south of the last three GFS runs with the vorticity moving just S of PR.

[Hammy]

Pitiful run from the Euro, which failed to even initialize anything more than a weak ITCZ trough.

[ninel conde]

llan Huffman ‏@RaleighWx 33m33 minutes ago

Global models show a trough over the eastern Caribbean with strong enough westerlies that will likely destroy Grace by later in week.

[gatorcane]

06Z Guidance, the IVCN (intensity consensus) is showing an increase now after 120 hours:

[cycloneye]

12z Guidance.

[ronjon]

Pretty good model consensus to the northern Leewards.

[cycloneye]

Over 30+kt shear in 120 hours.

Code: Select all

              * ATLANTIC     SHIPS INTENSITY FORECAST          *
                    * IR SAT DATA AVAILABLE,       OHC AVAILABLE     *
                    *  GRACE       AL072015  09/06/15  12 UTC        *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    40    43    45    48    50    51    51    48    44    41    39    37    37
V (KT) LAND       40    43    45    48    50    51    51    48    44    41    39    37    37
V (KT) LGE mod    40    43    45    47    49    51    50    48    45    42    39    38    37
Storm Type      TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP

SHEAR (KT)         5     4     4     4     7    13    12    18    22    26    23    30    33
SHEAR ADJ (KT)    10    12    10     8     5    10    11     7     6     4     2     0     0
SHEAR DIR        141   208   221   203   226   247   247   235   235   241   266   261   260
SST (C)         28.5  28.3  28.0  27.8  27.6  27.5  27.8  27.7  27.5  27.5  27.5  27.9  28.3
POT. INT. (KT)   145   142   138   135   133   132   135   134   132   132   131   136   141
ADJ. POT. INT.   146   144   138   135   132   131   135   134   130   130   129   132   136
200 MB T (C)   -53.2 -52.7 -52.7 -53.0 -53.0 -52.8 -53.0 -52.9 -53.1 -53.1 -53.3 -53.0 -53.0
TH_E DEV (C)       8     8     9     9     9    10    10    11    11    12    12    13    13
700-500 MB RH     54    52    49    50    49    48    48    47    47    46    45    47    46
MODEL VTX (KT)    15    15    14    15    16    15    14    13    11    10    10     9     9
850 MB ENV VOR    39    37    28    24    23    19    13     9     2    -8   -11    -6   -16
200 MB DIV         3   -10    -9    -2    -1    11    10    26    -7     8    -2    -7     2
700-850 TADV       1     2     1    -3    -3   -12   -12     2     0    -8    -5    -3     0
LAND (KM)       1284  1436  1589  1731  1873  1833  1617  1435  1258  1132  1039   887   762
LAT (DEG N)     12.7  12.8  12.9  13.1  13.2  13.5  13.8  14.1  14.3  14.6  14.8  15.4  16.0
LONG(DEG W)     29.2  30.7  32.1  33.4  34.8  37.5  40.3  43.1  46.0  48.9  51.8  54.3  56.4
STM SPEED (KT)    13    14    13    13    13    14    14    14    14    14    13    11    11
HEAT CONTENT       6     8    10    11    14    16    12    19    28    30    19    27    38

  FORECAST TRACK FROM OFCI      INITIAL HEADING/SPEED (DEG/KT):280/ 11      CX,CY: -10/  2
  T-12 MAX WIND:  35            PRESSURE OF STEERING LEVEL (MB):  518  (MEAN=624)
  GOES IR BRIGHTNESS TEMP. STD DEV.  50-200 KM RAD:  13.0 (MEAN=14.5)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD:  86.0 (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.  12.  12.  13.  14.
  SST POTENTIAL          1.   1.   2.   4.   6.  10.  13.  16.  18.  19.  20.  20.
  VERTICAL SHEAR MAG     1.   2.   4.   5.   6.   6.   6.   4.   1.  -1.  -3.  -6.
  VERTICAL SHEAR ADJ    -1.  -1.  -2.  -3.  -4.  -6.  -7.  -8.  -7.  -7.  -5.  -4.
  VERTICAL SHEAR DIR     0.  -1.  -2.  -3.  -5.  -8. -11. -14. -17. -18. -21. -22.
  PERSISTENCE            1.   1.   2.   2.   2.   2.   1.   1.   1.   0.   0.   0.
  200/250 MB TEMP.       0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.  -1.  -1.   0.
  THETA_E EXCESS         0.   0.   0.  -1.  -1.  -1.  -1.  -1.  -1.   0.   0.   1.
  700-500 MB RH          0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  MODEL VTX TENDENCY     0.  -1.   0.   0.  -1.  -2.  -3.  -6.  -7.  -7.  -8.  -8.
  850 MB ENV VORTICITY   0.   0.   0.   0.   0.   0.   0.  -1.  -1.  -1.  -2.  -2.
  200 MB DIVERGENCE      0.   0.  -1.  -1.  -1.  -1.  -1.  -2.  -2.  -1.  -1.  -1.
  850-700 T ADVEC        0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   1.   1.
  ZONAL STORM MOTION     0.   0.   0.   1.   1.   1.   1.   2.   2.   2.   2.   2.
  STEERING LEVEL PRES    0.   0.   0.   0.   1.   1.   1.   1.   2.   1.   1.   1.
  DAYS FROM CLIM. PEAK   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
  GOES PREDICTORS        1.   2.   2.   2.   3.   2.   2.   1.   1.   1.   1.   1.
  OCEAN HEAT CONTENT     0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.   0.
                        ----------------------------------------------------------
  TOTAL CHANGE           3.   5.   8.  10.  12.  11.   8.   4.   1.  -1.  -3.  -3.

   ** 2013 ATLANTIC RI INDEX AL072015 GRACE      09/06/15  12 UTC **
           ( 30 KT OR MORE MAX WIND INCREASE IN NEXT 24 HR)
 
 12 HR PERSISTENCE (KT):   5.0 Range:-49.5 to  33.0 Scaled/Wgted Val:  0.7/  1.9
 850-200 MB SHEAR (KT) :   4.6 Range: 28.8 to   2.9 Scaled/Wgted Val:  0.9/  1.1
 STD DEV OF IR BR TEMP :  13.0 Range: 37.5 to   2.9 Scaled/Wgted Val:  0.7/  0.9
 850-700 MB REL HUM (%):  58.8 Range: 43.2 to  93.5 Scaled/Wgted Val:  0.3/  0.4
 POT = MPI-VMAX (KT)   :  99.1 Range: 28.4 to 139.1 Scaled/Wgted Val:  0.6/  0.4
 Heat content (KJ/cm2) :   9.8 Range:  0.0 to 155.1 Scaled/Wgted Val:  0.1/  0.0
 D200 (10**7s-1)       :  -3.8 Range:-23.1 to 181.5 Scaled/Wgted Val:  0.1/  0.0
 % area w/pixels <-30 C:  80.0 Range: 15.3 to 100.0 Scaled/Wgted Val:  0.8/  0.1
 
 Prob of RI for 25 kt RI threshold=    24% is   2.0 times the sample mean(11.9%)
 Prob of RI for 30 kt RI threshold=    13% is   1.7 times the sample mean( 7.6%)
 Prob of RI for 35 kt RI threshold=     7% is   1.6 times the sample mean( 4.6%)
 Prob of RI for 40 kt RI threshold=     6% is   2.0 times the sample mean( 3.0%)

** PROBLTY OF AT LEAST 1 SCNDRY EYEWL FORMTN EVENT AL072015 GRACE      09/06/2015  12 UTC **
TIME(HR)   0-12  12-24(0-24)  24-36(0-36)  36-48(0-48)
CLIMO(%)     0      0(  0)       0(  0)       0(  0)     <-- PROB BASED ON INTENSITY ONLY
PROB(%)      0      0(  0)       0(  0)       0(  0)     PC4 UNAVAIL...MODEL SKILL DEGRADED

[gatorcane]

The 00Z UKMET certainly not showing dissipation east of the Leewards, 00Z 5-day graphic below:

[LarryWx]

Just like that, the 12Z GFS has a good bit less shear than the 6Z GFS. This run has shear near its center under 10 knots all of the way at least til it reaches 60W on Friday. Hmmm. Anyone else notice this?

[crownweather]

Just like that, the 12Z GFS has a good but less shear than the 6Z GFS. This run has shear near its center under 10 knots all of the way at least til it reaches 60W on Friday. Hmmm. Anyone else notice this?

Also, seems to keep Grace as an "entity" all the way to the Lesser Antilles and dissipates it in the eastern Caribbean.

[BobHarlem]

12Z looks almost identical to Erika's actual track and is also very weak and disorganized. The complacency factor for Florida after Erika is extreme, so I hope this doesn't get hyped because if it does, it really puts it in a bad position for when a real threat comes along.

[gatorcane]

The 12Z GEM now acknowledges Grace (though only shows 1014MB at initialization, too high) and has it going north of the Caribbean and bending west into the Northern Bahamas/Florida as a hurricane in the long-range. That would be a classic September Cape Verde track. Also develops another one in the Gulf.

186 hours making the turn:


240 hours:

[YoshiMike]

Lol where'd that second one come from? They must be thinking that something is gonna form spread in the gulf?

[gatorcane]

There are a cluster of 12Z GFS Ensembles that take Grace just north of the Caribbean and into the Bahamas, 240 hours below:

[ronjon]

This morning's Euro built in strong ridging over the west Atlantic in the 7-10 day timeframe. Looks like GEM forecasting that too in the long range. Might get interesting down the road if Grace survives.

[floridasun78]

i hope models don't do what their did with Erika make it hurr as get close leedwards

[LarryWx]

The latest Euro (12Z) again has Grace opening by 50W.