atlantic Tropical Storm Ida

[summer blizzard]

TD10 has formed just east of TD9. It should be in a low shear environment with warming seas for the next 5 days and will be 60mph in 4 days according to the NHC. Dry air could be an issue.

Track is WNW and slowing where the models diverge. Getting picked up by a trough would tug it north, the Euro apparently wants to keep it headed WNW though.

A bit of hope casting perhaps but if it avoids being picked up by the trough or hitting shear or dry air then it probably stands the best chance of being a decent hurricane eventually (bar Danny of course). Likely to be no threat to land.

[summer blizzard]

 

 

[summer blizzard]

A real beauty of a system tonight.

[summer blizzard]

 

TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 30 34 37 40 43 47 49 51 51 49 49 49 52
V (KT) LAND 30 34 37 40 43 47 49 51 51 49 49 49 52
V (KT) LGE mod 30 33 35 38 40 44 47 49 50 51 54 56 59
Storm Type TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP TROP

SHEAR (KT) 4 7 10 10 9 16 16 8 6 7 5 9 6
SHEAR ADJ (KT) 2 3 1 0 0 1 3 7 4 4 3 5 2
SHEAR DIR 216 261 280 291 286 282 286 285 267 256 233 243 218
SST © 27.8 27.7 27.7 27.8 27.8 27.9 28.0 28.2 28.3 28.5 28.6 28.8 28.8

 

Prob of RI for 25 kt RI threshold= 38% is 3.2 times the sample mean(11.9%)
Prob of RI for 30 kt RI threshold= 22% is 3.0 times the sample mean( 7.6%)
Prob of RI for 35 kt RI threshold= 9% is 1.9 times the sample mean( 4.6%)
Prob of RI for 40 kt RI threshold= 7% is 2.3 times the sample mean( 3.0%)

 

A long time since we've seen a system in a good environment (bar drier air).

[summer blizzard]

000
WTNT45 KNHC 182034
TCDAT5

TROPICAL DEPRESSION TEN DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
500 PM AST FRI SEP 18 2015

The cloud pattern of the depression has continued to improve, with
well-defined convective banding wrapping around the center. 1800
UTC Dvorak estimates from TAFB and SAB support tropical storm
intensity, but since ASCAT data from earlier this morning only
showed 20 kt of wind in the inner core, the initial intensity is
only being raised to 30 kt for now. Barring any unexpected
changes, the depression will likely be a tropical storm by this
evening. The environment appears generally conducive for gradual
strengthening during the next few days, but the global models
show that the cyclone will be located precariously beneath a narrow
upper-level ridge, especially on days 3 through 5. Even a slight
deviation from this pattern could put the cyclone in a higher-shear
environment and thus limit intensification, or even induce
weakening. The NHC intensity forecast continues to show gradual
strengthening through the forecast period and is close to a
consensus of the SHIPS and LGEM models.

The initial motion is 285/7 kt, with the depression being steered
by a mid-level anticyclone to its northwest. This anticyclone is
expected to move westward at the same pace as the depression during
the next few days, maintaining a west-northwestward motion through
48 hours. After that time, the steering currents are forecast to
collapse near the cyclone when a deep-layer trough amplifies over
the eastern Atlantic. As a result, the models show very slow
motion occurring by days 4 and 5, and the updated NHC track
forecast shows the cyclone becoming stationary at the end of the
forecast period. This forecast is largely unchanged from the
previous one and is near the middle of the tightly clustered
guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT 18/2100Z 13.4N 37.3W 30 KT 35 MPH
12H 19/0600Z 13.9N 38.4W 35 KT 40 MPH
24H 19/1800Z 14.9N 40.1W 40 KT 45 MPH
36H 20/0600Z 16.1N 42.5W 45 KT 50 MPH
48H 20/1800Z 17.2N 44.7W 50 KT 60 MPH
72H 21/1800Z 19.5N 47.6W 50 KT 60 MPH
96H 22/1800Z 20.5N 48.5W 55 KT 65 MPH
120H 23/1800Z 20.5N 48.5W 55 KT 65 MPH

$
Forecaster Berg

 

..

 

Expected to become a Tropical Storm tonight. Now forecast to reach 65mph by day 5.

[summer blizzard]

Now Tropical Storm Ida.

Forecast to reach 70mph and be close to hurricane strength in 3 days. Forecast to stabalise after as steering currents also collapse although some fodder models go as high as category 3.

[summer blizzard]

000
WTNT45 KNHC 191434
TCDAT5

TROPICAL STORM IDA DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
1100 AM AST SAT SEP 19 2015

As was noted yesterday, Ida will have an obstacle course to navigate
during the next several days, and the storm already appears to have
encountered its first hurdle. Westerly shear, on the order of 20 kt
according to UW-CIMSS analyses, has begun to affect the cyclone, and
the low-level center is now exposed to the northwest of the deep
convection. Dvorak CI numbers remain 2.5, and the initial intensity
therefore remains 35 kt. The SHIPS guidance indicates that the
vertical shear should be steady or even increase slightly during the
next 24 hours, so only slow strengthening is anticipated during that
time. The best window for more significant intensification appears
to be between 36 and 72 hours when the shear is forecast to
decrease. Another round of increased shear on days 4 and 5 should
limit strengthening or induce weakening. The intensity models are
split on Ida's future intensity, with the SHIPS and LGEM models only
modestly strengthening the cyclone through day 5 while the GFDL and
HWRF models bring Ida to hurricane strength by day 3. Due to the
uncertainty of how Ida will interact with the complex environment
around it, the NHC intensity forecast is a bit below the intensity
consensus and is very similar to the previous forecast.

Low- to mid-level ridging to the north and northeast of Ida is
inducing a slightly faster west-northwestward motion, or 295/10 kt.
The ridge is expected to weaken within the next 48 hours, leaving
Ida between two deep-layer lows, one located over the eastern
Atlantic and the other northeast of the Leeward Islands. This
should cause Ida to become nearly stationary or meander by days 3
through 5. With the exception of the UKMET model, the other track
models seem to be trending toward a solution in which the eastern
Atlantic trough has at least some influence on Ida's motion, and the
updated NHC track forecast now shows a slow eastward drift on days 4
and 5. Overall though, the NHC track forecast is very similar to the
previous one and is close to the model consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 19/1500Z 14.8N 39.7W 35 KT 40 MPH
12H 20/0000Z 15.7N 41.4W 40 KT 45 MPH
24H 20/1200Z 16.9N 43.4W 45 KT 50 MPH
36H 21/0000Z 18.2N 45.1W 50 KT 60 MPH
48H 21/1200Z 19.3N 46.5W 55 KT 65 MPH
72H 22/1200Z 20.5N 47.5W 60 KT 70 MPH
96H 23/1200Z 20.5N 47.0W 60 KT 70 MPH
120H 24/1200Z 20.5N 46.5W 55 KT 65 MPH

$
Forecaster Berg

[summer blizzard]

In terms of the models thoughts, both GFS12z and Euro 0z are very bullish after it's stalling stint. 0z Euro has it below 1000mb at day 5 and a 959mb hurricane at day 10. GFS has it below 1000mb at day 8 and steadily strengthening through day 16 where it's 973mb.

[summer blizzard]

Not much change. Slight strengthening as shear has begun to relax. Ida will have 48-72 hours to strengthen before the next shear hits and she stalls. By day 5, shear reduces. 

 

Models still the same. Steady strengthening from the GFS with a modest system, Euro has a 942mb hurricane by day 8.

[Somerset Squall]

Looks like Ida could be around for quite some time. However, it doesn't look at all healthy at the moment, with convection sheared away from the LLCC, leaving it almost completely exposed.

[summer blizzard]

Christ, look at the change overnight with the images in post 2.

Circular.

Vertically stacked.

Black (very strong) convention.

Would not be surprised to see it start strengthening at a good pace before the next shear bout.

[Summer Sun]

Heading for the UK in 10 days according to some of the papers this morning

[summer blizzard]

Ida is now a Tropical Depression and looking at satellite imagery its barely got a closed center.

The trough causing the shear is moving away and Ida is now moving west again as an upper ridge builds.

If you believe the shear maps and forecast then things will only get better and Ida should begin strengthening in a day or two but the 0z GFS did degenerate.

[Somerset Squall]

Ida continues to weaken and is on the brink of death. The storm has been moving erratically east-southeast through the day but is now pushing to the north. I think Ida will become a remnant low soon, though the official forecast holds on to Ida as a tropical depression for the next 5 days.

This is what you call a "drunken" system!

[summer blizzard]

Being the wierd and wonderful system that Ida is, its still alive.

If we believe the models then it will keep headed west over waters approaching 30C, shear will be fairly low and its speed reasonable.

The big fly in the ointment (and the reason the NHC suspect degeneration) is that the atmosphere is pretty dry (hence the exposed circulation) and unless it stacks and develops it wont be able to stop choking.

That should say choking.

[summer blizzard]

It be dead.