I should post the entire 5pm EDT Saturday discussion too because it was all worth reading, including about "the inner-core of the small cyclone has noticeably improved since the previous advisory". A small cyclone can develop much more rapidly. It can also weaken much more rapidly. It doesn't seem like it is forecast to become significantly bigger, in terms of its wind field, in the next 3 days which is the period in which wind field forecast data is available. Storms like this are very tricky and a line like "However, the low vertical wind shear and tight inner-core wind field are also harbingers of possible rapid intensification." is really important. It could also not become as strong as they forecast now. But the islands should be prepared for the more intense scenario and hope that maybe the dry air gets to it, if not shear to pick up earlier than forecast. But you can't count on that, you have to prepare for a hurricane, and one that could potentially be stronger than forecast.
Tropical Storm Dorian Discussion Number 2
NWS National Hurricane Center Miami FL AL052019
500 PM AST Sat Aug 24 2019
Visible and passive microwave satellite imagery indicate that the
inner-core of the small cyclone has noticeably improved since the
previous advisory. A 1705Z AMSR-2 overpass showed the development
of tightly curved bands and a 10 mile wide eye-like feature. In
addition, a 1935Z SSMI/S microwave pass revealed a tightly curved
band in 91 GHz data that wrapped almost 75 percent around the
center. Based on the much improved inner-core structure and 33-kt
wind vectors in an earlier ASCAT-B pass, the depression has been
upgraded to Tropical Storm Dorian on this advisory. Upper-level
outflow has been improving to the northwest, but remains slightly
restricted to the southeast due to some modest southeasterly
vertical wind shear.
The initial motion is 280/11 kt. The latest NHC model guidance
remains in excellent agreement that Dorian will generally move
west-northwestward for the next 5 days around the southern periphery
of the sprawling Bermuda-Azores high pressure ridge that is located
to the north of the Lesser and Greater Antilles. This motion is
expected to bring Dorian through the central or northern Lesser
Antilles on Tuesday, possibly as a hurricane, and then into the
northeastern Caribbean Sea on Wednesday and Thursday. The official
forecast track was shifted slightly north of the previous advisory
track, and is close to the consensus model TVCN, which remains north
of the NOAA HCCA corrected-consensus model.
The moderate to strong vertical wind shear that has been hindering
development of this system for the past several days is forecast to
diminish significantly during the next 12 h, and remain near 5 kt
through Tuesday. The low shear conditions, along with warm SSTs and
the significantly improved small, inner-core structure, should allow
for at least slow but steady strengthening despite the abundance of
dry mid-level air nearby. However, the low vertical wind shear and
tight inner-core wind field are also harbingers of possible rapid
intensification. For now, the new intensity forecast remains
conservative and similar to the previous advisory, and is above all
of the available intensity guidance, including the HWRF model.
Key Messages:
1. Dorian is forecast to strengthen and could be near hurricane
strength when it approaches the Lesser Antilles on Tuesday.
2. It is too soon to determine the specific timing or magnitude of
impacts in the Lesser Antilles, but tropical storm or hurricane
watches may be needed for a portion of the area on Sunday.
FORECAST POSITIONS AND MAX WINDS
INIT 24/2100Z 10.7N 49.1W 35 KT 40 MPH
12H 25/0600Z 11.0N 50.7W 40 KT 45 MPH
24H 25/1800Z 11.4N 52.8W 45 KT 50 MPH
36H 26/0600Z 11.9N 54.9W 50 KT 60 MPH
48H 26/1800Z 12.7N 57.0W 55 KT 65 MPH
72H 27/1800Z 14.6N 61.1W 65 KT 75 MPH
96H 28/1800Z 16.5N 65.3W 75 KT 85 MPH
120H 29/1800Z 18.4N 69.0W 70 KT 80 MPH...INLAND
$$
Forecaster Stewart
The current intensity is 35 knots. (40mph) As of the 8pm EDT SHIPS intensity output, there remains a 33% chance of a 65 knot (75mph) increase over 3 days. That would be 100 knots. (about 115mph)
Here is the path used for the SHIPS intensity output at 8pm EDT:
http://hurricanecity.com/models/models.cgi?basin=al&year=2019&storm=05&display=google_map&latestrun=1&models=OFCI
SHIPS intensity output at 8pm EDT Saturday:
ATLANTIC 2019 SHIPS INTENSITY FORECAST
IR SAT DATA AVAILABLE, OHC AVAILABLE
DORIAN AL052019 08/25/19 00 UTC
TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 35 37 40 43 46 52 59 67 69 72 72 71 71
V (KT) LAND 35 37 40 43 46 52 59 67 69 72 72 71 53
V (KT) LGEM 35 37 39 42 44 51 58 65 70 71 70 68 51
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP
SHEAR (KT) 8 5 4 5 3 10 4 11 17 12 14 18 8
SHEAR ADJ (KT) 2 3 2 2 4 0 -2 0 -8 -4 0 -6 0
SHEAR DIR 138 120 62 43 14 352 313 291 247 252 214 245 208
SST (C) 28.0 28.0 28.0 28.2 28.3 28.6 29.0 29.1 29.3 29.2 29.2 29.1 29.2
POT. INT. (KT) 137 137 137 140 141 146 152 154 157 155 155 153 155
ADJ. POT. INT. 137 136 135 139 141 145 151 153 155 150 149 146 147
200 MB T (C) -53.8 -54.0 -54.2 -54.1 -54.1 -54.4 -54.0 -54.1 -53.8 -54.3 -54.2 -54.4 -54.2
200 MB VXT (C) -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.3 -0.2 -0.2 -0.2 -0.1 -0.2 -0.2
TH_E DEV (C) 9 9 10 10 10 10 10 10 11 11 12 11 12
700-500 MB RH 42 39 38 39 41 43 45 49 47 49 50 53 55
MODEL VTX (KT) 13 12 12 11 11 10 10 11 8 8 7 6 4
850 MB ENV VOR 39 28 17 18 16 9 12 11 8 19 18 6 1
200 MB DIV -5 -14 -26 -23 -8 -10 -10 27 10 27 43 -3 9
700-850 TADV -7 -7 -7 -6 -5 -3 0 1 -2 0 0 2 -5
LAND (KM) 714 690 668 651 653 569 413 369 487 256 121 61 -25
LAT (DEG N) 10.8 11.1 11.3 11.5 11.6 12.3 13.2 14.0 15.3 16.2 16.9 17.8 19.1
LONG(DEG W) 49.7 50.8 51.8 52.8 53.9 56.0 58.1 60.1 62.3 64.4 66.3 68.2 69.9
STM SPEED (KT) 11 11 10 10 11 11 11 12 12 10 10 10 10
HEAT CONTENT 12 11 12 14 19 36 42 38 54 49 69 83 68
FORECAST TRACK FROM OFCI INITIAL HEADING/SPEED (DEG/KT):280/ 11 CX,CY: -10/ 2
T-12 MAX WIND: 30 PRESSURE OF STEERING LEVEL (MB): 538 (MEAN=620)
GOES IR BRIGHTNESS TEMP. STD DEV. 50-200 KM RAD: 16.9 (MEAN=14.5)
% GOES IR PIXELS WITH T < -20 C 50-200 KM RAD: 52.0 (MEAN=65.0)
PRELIM RI PROB (DV .GE. 35 KT IN 36 HR): 12.0
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. 10. 11. 11. 12. 12.
SST POTENTIAL 1. 1. 1. 2. 4. 8. 14. 19. 23. 26. 28. 31.
VERTICAL SHEAR MAG 1. 2. 3. 4. 6. 8. 9. 9. 8. 8. 7. 7.
VERTICAL SHEAR ADJ 0. 0. 0. -1. -1. 0. 0. 2. 3. 2. 2. 2.
VERTICAL SHEAR DIR 0. 0. 1. 2. 3. 3. 3. 2. 0. -1. -2. -3.
PERSISTENCE 1. 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0.
200/250 MB TEMP. 0. 0. -1. -1. 0. 0. 0. 0. 0. 1. 1. 2.
THETA_E EXCESS 0. 0. 0. 0. 1. 1. 1. 1. 1. 1. 1. 1.
700-500 MB RH 0. 0. 1. 1. 1. 2. 3. 3. 3. 3. 2. 2.
MODEL VTX TENDENCY 0. -1. -1. -2. -3. -4. -5. -9. -10. -13. -15. -17.
850 MB ENV VORTICITY 0. 0. 0. 0. 0. 0. 0. -1. -1. -1. -1. -1.
200 MB DIVERGENCE 0. -1. -1. -1. -2. -1. -1. -1. -1. 0. 0. 1.
850-700 T ADVEC 0. 0. 0. 0. -1. -1. -1. -1. -1. 0. 0. 0.
ZONAL STORM MOTION 0. 0. 0. 0. 0. 1. 1. 1. 1. 2. 2. 2.
STEERING LEVEL PRES 0. 0. 0. 0. 1. 1. 0. 1. 1. 1. 1. 1.
DAYS FROM CLIM. PEAK 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
GOES PREDICTORS 0. 0. 0. 0. 0. -1. -2. -2. -2. -2. -2. -2.
OCEAN HEAT CONTENT 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
RI POTENTIAL 0. 0. 0. 1. 1. 1. 0. 0. 0. 0. 0. 0.
----------------------------------------------------------
TOTAL CHANGE 2. 5. 8. 11. 17. 24. 32. 34. 37. 37. 36. 36.
CURRENT MAX WIND (KT): 35. LAT, LON: 10.8 49.7
2019 ATLANTIC RI INDEX AL052019 DORIAN 08/25/19 00 UTC
(SHIPS-RII PREDICTOR TABLE for 30 KT OR MORE MAXIMUM WIND INCREASE IN NEXT 24-h)
Predictor Value RI Predictor Range Scaled Value(0-1) % Contribution
12 HR PERSISTENCE (KT) : 5.0 -49.5 to 33.0 0.66 6.1
850-200 MB SHEAR (KT) : 5.1 30.1 to 2.3 0.90 3.2
HEAT CONTENT (KJ/CM2) : 13.6 0.0 to 151.8 0.09 0.3
STD DEV OF IR BR TEMP : 16.9 36.6 to 2.8 0.58 2.2
MAXIMUM WIND (KT) : 35.0 22.5 to 137.5 0.33 0.7
2nd PC OF IR BR TEMP : -0.6 2.9 to -2.9 0.60 1.5
POT = MPI-VMAX (KT) : 102.9 27.5 to 139.6 0.67 1.7
D200 (107s-1) : -15.2 -29.7 to 185.9 0.07 0.1
%area of TPW <45 mm upshear : 40.8 100.0 to 0.0 0.59 0.0
BL DRY-AIR FLUX (W/M2) : 313.4 895.4 to -55.0 0.61 0.0
SHIPS Prob RI for 20kt/ 12hr RI threshold= 7% is 1.3 times climatological mean ( 5.2%)
SHIPS Prob RI for 25kt/ 24hr RI threshold= 23% is 2.1 times climatological mean (10.9%)
SHIPS Prob RI for 30kt/ 24hr RI threshold= 16% is 2.3 times climatological mean ( 6.9%)
SHIPS Prob RI for 35kt/ 24hr RI threshold= 12% is 2.7 times climatological mean ( 3.8%)
SHIPS Prob RI for 40kt/ 24hr RI threshold= 10% is 4.6 times climatological mean ( 2.4%)
SHIPS Prob RI for 45kt/ 36hr RI threshold= 13% is 2.8 times climatological mean ( 4.5%)
SHIPS Prob RI for 55kt/ 48hr RI threshold= 21% is 4.5 times climatological mean ( 4.6%)
SHIPS Prob RI for 65kt/ 72hr RI threshold= 33% is 6.2 times climatological mean ( 5.4%)
Matrix of RI probabilities
------------------------------------------------------------------------------
RI (kt / h) 20/12 25/24 30/24 35/24 40/24 45/36 55/48 65/72
------------------------------------------------------------------------------
SHIPS-RII: 6.7% 22.5% 15.7% 11.8% 9.5% 12.6% 20.8% 33.3%
Logistic: 6.1% 26.3% 21.1% 9.9% 4.9% 14.7% 18.6% 21.2%
Bayesian: 0.5% 11.8% 2.6% 0.0% 0.0% 0.9% 2.0% 0.6%
Consensus: 4.4% 20.2% 13.1% 7.3% 4.8% 9.4% 13.8% 18.4%
DTOPS: 1.0% 2.0% 1.0% 0.0% 0.0% 0.0% 3.0% 5.0%
## ANNULAR HURRICANE INDEX (AHI) AL052019 DORIAN 08/25/19 00 UTC ##
## STORM NOT ANNULAR, SCREENING STEP FAILED, NPASS=4 NFAIL=3 ##
## AHI= 0 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##
PROBLTY OF AT LEAST 1 SCNDRY EYEWL FORMTN EVENT AL052019 DORIAN 08/25/2019 00 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) <-- FULL MODEL PROB (RAN NORMALLY)
DSHIPS INTENSITY FORECAST ADJUSTED RELATIVE TO ONSET OF ERC WEAKENING PHASE
TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
>24HR AGO (DSHIPS) 35 37 40 43 46 52 59 67 69 72 72 71 53
18HR AGO 35 34 37 40 43 49 56 64 66 69 69 68 50
12HR AGO 35 32 31 34 37 43 50 58 60 63 63 62 44
6HR AGO 35 29 26 25 28 34 41 49 51 54 54 53 35
NOW CURRENT INTENSITY < 83 KT
IN 6HR INTENSITY IN 6HR < 83 KT
IN 12HR INTENSITY IN 12HR < 83 KT
From bottom of this folder: https://ftp.nhc.noaa.gov/atcf/stext/
I highlighted the land version of SHIPS, which takes land into account, since the last point has it over Hispaniola. If it missed the island, or any land through that point, it could be the version without land. |