Tuesday, August 26, 2014

Cristobal, Rafael, and Sandy.

A little bit more on what I was saying on my Facebook weather page, about the tropical pattern last night.

The pattern looks very October like.... with the deep trough and the cold front along the Gulf Coast. This front is what has caused the convection to flare up along the southern coast.  Rule of thumb, always be aware of frontal bounties  in the Gulf in August. The waters in the Gulf are very warm this time of year.  So even if we don't have great convergence over the Gulf. it does bear watching.

The pattern over the Atlantic has gotten my attention. We have all that October like cool and dry air associated with the trough to the west of Hurricane Cristobal, and a nice southerly flow of the eastern trade wind being pulled north by the front and trough, on Cristobal's east side.
The above image shows how the wind flow is steering Cristobal.
Normally the easterly trade wind flows westward across the Tropical Atlantic into the Caribbean. But as I show on the image the trade winds are being pulled to the north.

Since the trades are not pushing the air into and out of the eastern Caribbean and part of the Atlantic, they are more or less just sitting around and pilling up with nowhere to go. 

Hurricane Cristobal will be moving to the northeast over the next few days. Once he is out of the way  and the trough relaxes, we will see the easterly  trades move back into a normal flow into the Caribbean.

Many times when this happens,  the build of air and all that convergence is redirected back into the western Caribbean as a low amplitude wave of low pressure and convergence, can cause development in the western Caribbean and GOM ( Gulf of Mexico).

The last time this sort of pattern was in place was back in October of 2012 when we had Hurricane Rafael  in the same general position in the Caribbean.  He had a track that was quite similar to what we expect Hurricane Cristobal to have.  Rafael moved east of Bermuda as a hurricane, whereas Cristobal is going to past west of Bermuda, but all in all the tracks will end up much the same.  Back in October of 2012 we also had a deep trough along the east coast ,  helping steer Rafael away from the east coast.  We also had the trade winds bending to the north and away from the western Caribbean.
              The low out over the Atlantic in the above image is Rafael moving north and east.

After Rafael moved north and then northeast out into the north central Atlantic, we had an area of low pressure develop  in the western Caribbean a few days later around the 20th of October ,  south of Jamaica, Haiti, and the Dominican Republic.  This low was caused by the redirection of the trades and convergence into the Caribbean .  In a few days this area of low pressure developed into Tropical and then Hurricane Sandy.  From here she tracked north, thanks to Rafael moving to the northeast and clearing her path. 
                                                                                                                             October 20 2012

       Oct 24, 2012 showing Sandy starting her northward move out of the Caribbean

       October 28, 2012 showing Sandy moving off the East Coast.

A couple of surface charts showing the trough and front positions during that time in Oct of 2012

You can see the two surface charts , with the trough and fronts looking much the same as the charts I've been posting on my weather page quite a bit this year...

Back to Cristobal, he will have a path much like Rafael ending up southeast of the Canadian Maritimes  just as Rafael did.

                                                                      Showing Sandy moving out of the Caribbean and Extratropical Rafael off the Maritimes.

Rafael's Track
Cristobal's Track

The models aren't seeing anything  tropical end of the weekend into the first part of next week..... But they do show some ridging along the Northeast and East Coast of the US, along with lowering pressures in the western Caribbean.



Here is the GFS showing pressures lowering in the western Caribbean as we head into next week. You can see Cristobal is in the same position that Rafael was off the Maritimes.

Pattern recognition is a very important skill when it come to forecasting weather.  I'm not saying we will see a repeat of Sandy, only that the setup is there that lead to her birth.  So we need to keep a close eye  on the Caribbean first part of next week........ with the Tropics , you never know.


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