Alastair Thompson Profile picture
Sep 30 12 tweets 8 min read
The NHC's forecasting for #HurricaneIAN remains tricky. Inching closer to the North/South Carolina border. And from satellite data, it looks possible that the center of #HurricaneIan is east of the current line.
The specialist HRRR model, which proved more accurate than the main models in predicting the path across Florida is now in agreement with ECMWF, GFS and NAM-CONUS on the location of landfall, but there is a broad range of intensity from 973-984 mb.
There is also a 6 hour range in arrival time among the four models from 1pm to 7pm. Due to the size of the storm, the impacts of #HurricaneIAN on the Carolinas & beyond are already well and truly underway over night local time.
So lets look at the satellite imagery. For this I am using the CMISS tool suite - an open source suite that utilises the live satellite floater data feeds - and highlights the important features - location and strength of convection and rotation.
Whilst #Hurricane Ian has strengthened a little the extent of the shear it is experiencing is very very high - which you can see as the center of circulation is only has convection to the north. Remarkably though it is still comitted to turning to the North West regardless.
From what I can discern the actual center of circulation is now considerably south of the the pointy cloud element on the LHS.
CONCLUSION: On that basis of this I think #HurricaneIAN is moving slower than expected - and East of where forecast therefore not on the current track. Landfall may therefore be further East of forecast in the direction of to Myrtle Beach/Wilmington.
Given this, I think it is important for the NHC to provide media with a live stream of accurate positioning data, as the graphics which have been broadcast throughout this storm since landfall in Florida, have often been wrong.
In this - latest live satellite image - it is clar that the storm is continuing to move north eastwards (the land is moving South West) and by now according to the track #HurricaneIAN is supposed to be moving North.
The Radar imagery here is a tell. #HurricaneIAN mayhave even stalled - which would explain its ability to develop rain bands in a circle - their appearance on sunrise also makes sense.
This is not good news as the longer the storm spends over water the stronger it is able to become. Its ability to do so whilst experiencing 50knots of shear is extraordinary.
The sun has not yet risen on #HurricaneIAN.

The first image shows the circulation location and size as indicated (approximately) by radar (4th image) .

2nd image shows the direction Ian is supposed to be going.

3rd shows position it is supposed to be in per the NHC forecast.

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More from @althecat

Sep 30
I've been trying to figure out how best to visually explain how weird #HurricaneIAN is. This is the perfect illustration.

#HurricaneIAN will split in two, the Western part will head to the Virginias, for a while and then return to the Atlantic coast probably in Maryland.
#HurricaneIAN is a remarkable, and hopefully very unsuual phenomena, two distinct weather systems working together - that have appeared to be a single system for several days.

This, the final act, may be the most extraordinary part of this event. But not the most destructive. ImageImageImageImage
This CMISS animation shows what is happening vert clearly. And this explains a lot about #HurricaneIAN:
- its strength
- its super rapid intensification
- the persistent short range model forecast error
- its ability to remain intact over land
Read 5 tweets
Sep 30
This is what I was worried about the interaction between the atmospheric river and #HurricaneIAN.

The Wastern leading edge of the Atmospheric River is now pumping directly into #IAN and it appears to be strengthening over land. The Eyewall is not yet complete. Image
A closeup satelite view of what is likelu the center of #Hurricane IAN coming ashore at Charleston half an hour ago. Image
Read 7 tweets
Sep 30
What is happening in the Carolinas is not just a hurricane. The catastrophic event ahead is probably more due to the Atmospheric River which #HurricaneIAN has directed onshore. The second image here roughly delinates the two.

On the ground however this is one weather event. ImageImage
More on the #HurricaneIAN - Atmospheric River combination, to understand this event in context, this is a very important part of the story.

#ExtremeWeather #ClimateChangeNow.
This thread also looks at this issue. #HurricaneIAN has been embedded in this atmospheric river since it started intensifying explosively.

This combination is I think pretty unusual, and it may lead to unexpected consequences in the Carolinas.
Read 4 tweets
Sep 30
#HurricaneIAN update.

Four radar images over an hour 1-2pm UST.
#HurricaneIAN's motion is not as expected/forecast.

With sunrise approaching energy from the sun increases visibility of the circulation with the development of rain bands in the South Eastern quadrant. ImageImageImageImage
Spaghetti guidance is tightly clustered on Charleston landfall. After moving inland a very sharp turn W/SW is expected with some models even predicting a return back to the Carolina coast.

Tropical rain all the way to the Great Lakes is possible/likely given the size of Ian. ImageImageImage
Intensity guidance is very clear that the storm is expected to weaken - based on landfall today. This will change rapidly if Ian does not weaken or landfall quickly. Image
Read 15 tweets
Sep 29
#ExtremeWeather #ClimateChangeNow

#HurricaneIAN Update thread.

Near live 6hr satellite imagery #IAN beginning its exit of Florida over Cape Canaveral and the Kennedy Space Center. And it looks like it started strengthening significantly before it's center crossed the coast.
This wider angle view helps put the storm into wider perspective, in particular its size, and the importance and significance of the massive convective area to the East of Florida from which #TSIan #HurricaneIAN is being fuelled.
The big question now is how will #HurricaneIAN interact with this atmospheric river as it crosses the Atlantic heading towards the Carolinas, specifically, will this extremely complex moist air field strengthen or inhibit intensification.
Read 12 tweets
Sep 29
This image shows why #HurricaneIAN was so strong. A Parallel line of supercells in an atmospheric river feeding of the hurricane, and in return providing a much larger area of Convection. And this is also the case with Super Typhoon Noru on the other side of the Pacific.
Interestingly #Noru's burst of intensification on approach to Vietnam coincided with part of the intensification period of #HurricaneIAN
Read 4 tweets

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