20% Yellow Circle in Caribbean. Why Hurricanes Form in June in the Carib and why they head North into the GOM and BOC. Tropical Birthing Lesson From BobbiStorm ;)

A 20% yellow circle has popped up on the 5 day page at the NHC website. This is the general area we have been watching for days now as models have consistently indicated where something could form. Think of this more as a "formation zone" vs where a tropical, named system will go down the road. There is nothing specific there now to see. The image above looks much like a yellow beach ball sitting on the ledge of Honduras which I speak about often if you read this blog from season to season. It's a zone where June named storms often form and is climatologically favorable.

You can see why in the loop below.

The water warms up fastest there.

Far from cold fronts.

It's a small womb like area.

Protected on most sides.

Yucatan to the North and West.

The ledge of Honduras below.

Cuba to the NE.

West bound tropical waves find this zone easily.

Try to edge outside your scientific box and try to visualize this area in another way. It's almost as if this area is a tropical uterus for June and July Hurricanes. It's a Neptunian womb where low pressure exists over warm water that acts as an incubator for any moist convection that lingers too long within that safe zone. it oozes tropical energy and right there in that protective cove like region where the water is hot on any given day when the shear slows down a bit the steam rises; storms congregate and it becomes the impulse for intensification up to the next level of tropical development. Then, after days of watching you blink your eyes as the area is suddenly blessed with a yellow circle on the NHC site. And, then you keep watching to see what happens and if this yellow circle might grow up and become Bret. Well actually first you wait for a floater to be designated to watch it endlessly for development into Bret. The floater and a designation as an Invest is the next stop in the birth of a tropical entity.

I could explain this in purely mathematical, scientific terms with my expertise in weather history, however then you would not be on my blog would you? I'll leave that to the young guns who develop models and apps and debate meteorological abbreviations on Twitter late at night. I'm trying to paint a picture you can see and feel for why this region is watched this time of year as much as the Bay of Campeche that is another womb like area that tends to easily incubate low pressure and deal with named storms often in June and July. I've been prone to joke that every season we need to sacrifice one name to the BOC before we can move on and deal with true Atlantic Hurricanes. It's historically accurate to expect something in this region to tease us with the possibility of advisories, cones, watches and warnings.

Let's look at this area in parts.

First let's look at the Caribbean above.

You can see the area lower left.

Also note a persistent westbound wave in the Atlantic.

Shear usually blows those early waves apart.

We look up below into the GOM.

The BOC is not ready just yet.

There's a spin South of Nola.

Shear is stills strong.

But it's a compelling loop.

But, nothing really there to see just yet.

Remember this is a 5 day Yellow Circle.

In 5 Days something might develop.

It's popular this year to call this region a gyre. 

A term last used for the missing Malaysian plane..

...and the South Pacific waters.

Never mistake a gyre for circulation is the rule here.

Another rule is that we count about a week to ten days after something forms in the Epac for development in the Caribbean. It's not a hard fast rule and it also depends if something else forms in the Epac. You can only have so much tropical energy in one region, one robs the other to develop and often in the wake of one's departure the other area to the East in the Caribbean pulls itself together.

Nice to be back home in Raleigh. I live in two cities, Miami and Raleigh and though I'm not the biggest fan of Raleigh if you can call the Carolinas your second home you are lucky as it's a beautiful place to be. 

The process of tropical development is slow in June and the models scream development, then whisper development, then they lose development and then they see it again. They are models that are used to forecast development in the long term. Remember that THIS SEASON we have NEW RULES and the NHC can, could and will issue at some point a cone for forecast development. Let's say an area in the GOM close to shore looks to be pulling together say just south of Mobile Alabama. Things percolate fast over warm waters close to shore. IF the models predict development and all agree on a tropical storm quickly ramping up before landfall to a Category 2 Hurricane (as has happened many times) AND the NHC forecasters believe the models are correct and agree on formation they can issue watches and warnings before a named storm is even christened on TWC with headlines and local news breaking into General Hospital to stay tuned for the local news and information on soon to be Tropical Storm Bret. The game is the same but the rules have changed this year and that's a good thing.

The loop below shows where tropical moisture is headed, moisture, precipitation and all those elements that come together to show steering currents or development. A strong ITCZ with moisture flowing west, sliding along the North coast of South America. That moisture finds itself in the yellow circle the NHC has designated for possible development in the 5 day time period. Then watch the moisture from the Epac riding North towards the Yellow Circle area and the BOC. it's a process and you have to wait to see something really form. The area is fed by moisture from both directions and then it sits, lingers over warm water and low pressure begins to develop.

Currently nothing has formed or is about to form.

https://earth.nullschool.net/#current/wind/isobaric/1000hPa/orthographic=-67.61,17.40,741

I know you want to know about the models.

Last frame on one run.

It shows a Low formed and hooking left.

Landfall south of the border on this run.

http://www.tropicaltidbits.com/analysis/models/?model=ecmwf&region=atl&pkg=mslpaNorm

You can play with the link above. I'm not into discussing model possibilities and differences this morning as much as pointing out the overall possibilities. Just as easily as the above ending to the story of Bret it could also form elsewhere and head elsewhere if and when conditions are suddenly just right. This time of year things spin up fast close in be it the Yucatan coast, Florida coast or along the beach towns of the Gulf of Mexico so stay tuned. Oh..........and it's going to be a messy time for anyone vacationing down by Acapulco. But, it's that time of year so what else is new? I went a bit long on discussion this morning as I am finally home for the first time in two weeks and I really want to set the stage for the story that may unfold in about five days time or less...or more. And, I suppose I owe a few people a real BobbiStorm blog post. I'll update if anything changes and the next blog post will be about model discussion for that area and a few others I'm watching. Have a wonderful day...

Besos Bobbistorm

Follow me on Twitter at @Bobbistorm for faster updates.

Ps The region where the yellow beach ball is sitting covers the spot where divers love to dive. Watch the video below and you'll see why.