re: Hurricane Irma - Spinning Down

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Aw man this bitch has here eye on the Gulf

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I know everyone keeps worrying about this, and it certainly can happen, but folks along the eastern coast of the US are still far more likely to seen an impact than we will along the GOM.

This is gonna be bad

Is that landfalling with 895 mb? Jesus

What is the confidence level of a turn north to FL? I recall the earlier Karina tracks had a turn north to FL that didn't occur until much later.

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Moving forward, to just before the images in the quote, and notice that the reflection of the ULL is still there north of the Islands in the GFS 500mb anomaly map but is basically gone on the Euro.



So basically, the Euro is replacing the ULL with high pressure faster than the GFS. This keeps Irma farther to the SW and isn't allowing it to escape to the NW.

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So we have been watching that tricky little ULL to the NW of Irma since last week and it has slowly been weakening in the model forecast. Here is the forecast from a few days ago for when Irma is approaching the Islands and getting ready to make the turn.



Notice that the reflection of the ULL to the NW of Irma shows up in the 500mb height anomaly maps. This was creating a weakness that was allowing Irma to get to the NW making it easier for the upstream trough to kick it OTS.

Now lets look at the model trend:



Notice that the ULL is showing a weakening trend and this is allowing for a stronger ridge over the top of Irma.



Now, this is just one of many moving parts but it is allowing the ridge to drive Irma farther to the west before the turn can start. This is totally ignoring the upstream trough that tries to turn Irma back to the north. However, there is probably a point that Irma gets far enough west that a faster or weaker trough might totally miss Irma. The pattern gets too complicated down the road to discuss those options.

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The pattern gets too complicated down the road to discuss those options.

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It's complicated sux arse

Here is a ride along of Hurricane Matthew. You can click to look around.

LINK

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Hurricane Irma Advisory Number 21
NWS National Hurricane Center Miami FL AL112017
1100 AM AST Mon Sep 04 2017

...HURRICANE WARNINGS ISSUED FOR PORTIONS OF THE LEEWARD ISLANDS...
...HURRICANE WATCHES ISSUED FOR THE BRITISH AND U.S. VIRGIN ISLANDS
AND PUERTO RICO...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
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LOCATION...16.8N 53.3W
ABOUT 560 MI...905 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H
PRESENT MOVEMENT...WSW OR 255 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...944 MB...27.88 INCHES

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Hurricane Irma Discussion Number 21
NWS National Hurricane Center Miami FL AL112017
1100 AM AST Mon Sep 04 2017

The satellite presentation of Irma has improved markedly over the
past 24 hours, with the eye becoming larger and much more distinct.
A NOAA Hurricane Hunter aircraft has reported peak 700-mb flight
level winds of 117 kt, SFMR winds of 107 kt, and dropsonde data
that support a minimum pressure of around 944 mb. These data
support an initial intensity of 105 kt. The aircraft also reported
concentric eyewalls and a double wind maximum during the last couple
of passes through the center, indicating that an eyewall
replacement cycle has likely begun.

Irma is expected to remain within a very favorable environment for
strengthening during the next several days and additional
intensification appears likely. However, eyewall replacement cycles
are likely to cause some fluctuations in intensity during that time.
The NHC forecast brings the hurricane to category 4 strength within
the next 24 hours, and then maintains Irma as a powerful hurricane
during the next 5 days, assuming that the core of the cyclone does
not move over any of the Greater Antilles.

Irma has been moving west-southwestward or 255/11 kt to the south of
a strong mid-level ridge over the central Atlantic. The hurricane
should turn westward later today or tonight, then west-northwestward
Tuesday as it reaches the southwestern portion of the ridge. As
mentioned in the previous NHC discussion, a large mid-latitude
trough is expected to amplify over the eastern United States during
the next few days. The global models are unanimous in lifting the
trough out to the northeast by late in the week, allowing the
Atlantic ridge to build westward on days 3 through 5. The track
guidance has again shifted westward and southwestward at days 4 and
5, but the models remain in very good agreement through the forecast
period. The updated NHC track forecast has been adjusted
southwestward late in the period, and lies very near the consensus
of the ECMWF, GFS, and HWRF models.

Six hourly upper-air soundings will begin at 1800 UTC today over the
central United States to better sample the upstream mid-latitude
trough. In addition, the NOAA G-IV aircraft will begin sampling the
environment around Irma this afternoon and evening, and these data
will be included in tonight's 0000 UTC model runs.

Users are reminded to not focus on the exact forecast track since
strong winds and heavy rainfall extend well away from the center.
In addition, average NHC track errors are about 175 and 225 statute
miles at days 4 and 5, respectively.

KEY MESSAGES:

1. Irma is expected to affect the northeastern Leeward Islands as a
dangerous major hurricane, accompanied by life-threatening wind,
storm surge, and rainfall impacts, along with rough surf and rip
currents. Hurricane warnings have been issued for portions of the
Leeward Islands. Preparations should be rushed to completion, as
tropical-storm force winds are expected to first arrive in the
hurricane warning area by late Tuesday.

2. Irma could directly affect the British and U.S. Virgin Islands
and Puerto Rico as a dangerous major hurricane later this week.
Hurricane watches have been issued for these areas, and tropical-
storm-force winds could arrive in these areas by early Wednesday.

3. Irma could directly affect Hispaniola, the Turks and Caicos, the
Bahamas, and Cuba as a dangerous major hurricane later this week.
Residents in these areas should monitor the progress of Irma and
listen to advice given by officials.

4. There is an increasing chance of seeing some impacts from Irma in
the Florida Peninsula and the Florida Keys later this week and this
weekend. In addition, rough surf and dangerous marine conditions
will begin to affect the southeastern U.S. coast by later this week.
Otherwise, it is still too early to determine what direct impacts
Irma might have on the continental United States. However, everyone
in hurricane-prone areas should ensure that they have their
hurricane plan in place, as we are now near the peak of the season.