From an apparent next-to-nothing setup on Midnight 7/3 (0000 UTC 7/4) three storm centers have developed in or near the Caribbean Sea in thirty hours.
The tropical wave 97L has been working its way west through a SAL that it has weakened with a lungeE-retrenchW-organizeInPlace mode of action. The wave appeared to try to freeze or stop under the upper level high at 16N65W (?) in the NE corner of the Caribbean as the circulation repeatedly pushed LL storms under the ridge to the NW (with a SW-NE axis, retreating to the NE). Additionally, the 97L center continually worked towards a point just east of a peak in the shearing westerly flow that crosses the southern Caribbean / northern South America. The ridge was diverting some of the westerlies off to the NE but began to pull out on 7/4, finally weakening into a ridge being drawn across the central Atlantic (by & under the flat path of the jet from the US mid Atlantic plowing straight across the ocean).
At the same time, other tropical storm centers setup off the northern coasts of Panama and Brazil in an isosceles triangle with 97L - each essentially equidistant from 97L to the SW and SE. The westerly shear that is supposed to suppress tropical storms in an El Nino [Modiki?] year was converted by this system of three storms into an ally. Each of the storms repeatedly and sometimes continually fed its current moisture mix forward to the next storm to the west under the shear while each storm pushed outflow on top of the westerlies to ride back one storm to the east. The outflow on top + feed flow underneath dampens the westerlies which makes them heavier and slower (less of a threat).
[N.B. Storms create backflow under shearing westerlies here from two causes: the e->w backflow is the general trend across the basin (goes with the flow), and feed forward to the west, under the westerlies flowing east, is a low/no energy move (conserves momentum locally without other movement == no exchanges to/from other areas).
As the jet dragged out the ridge [along 75W in f'cast?] the westerly flow changed because little or none of its volume was diverted to the northeast by the fading fleeing ridge. As the bend in the westerly flow shifted to the west, all three storms (97L and its companions to the east and west) simultaneously made a lungeWest-retrenchEast-organizeInPlace movement between the hours of 300-800 UTC on 7/5. 97L and 98L(?), its companion storm to the east, both made a step up in intensity by expanding, increasing outflow and taking the form of an incipient tropical cyclone. The third storm to the west grew larger but has not yet fully organized SE of Nicaragua and NE of Panama. As dawn breaks at 1015 UTC 7/5 two brand new TCs have a full day to develop with a third very likely to form farther west, again, as dawn breaks there.
What is really happening here?
There is definitely a pattern in the way the storms are arranged but it could be that the pattern is simply the shape of the band of westerly shear. Similarly, the feed forward+feed back loops between the storms are driven by the strong HL westerlies. The simultaneous moves and expansion could just be a concurrent response to the change in the common element - the band of westerly shear. There is evidence here of a larger system, but it may just be that the larger system is 'the weather in the tropics'.
There is a pattern, but is there a pattern besides the shape of the westerly flow?
I think that this is a higher order mode of response of the tropical weather system. It is an adaptation to the geography of the Caribbean that lays out storms in a triangular pattern that lays out several small storms over an area that is greater than all but the very largest storms. If this multi-center pattern is truly a self-organizing and self-sustaining system, it will likely show itself as such.
The pattern could demonstrate that it is a system by:
-- Expanding beyond the three storms currently associated with the westerlies. This could take place in a few different spots:
-- -- development of the existing storm (in pattern to the SE) at <5N on the Brazil coast. This would be striking as it would be a very low latitude TC.
-- -- development of a new TC to the NE of 97L. This would be striking as it is next to the only place left in the Atlantic where the SAL retains its potency as a water vapor killer.
-- -- development of a new TC to the NW of 97L (in or N of Bahamas). This would be striking as it is a dryish spot and up against the developing ridge.
-- -- development of a new TC east of 97L &/or east of 98L in the same pattern. East of 97L would be more striking as it is in the SAL worse than the position NE of 97L. The spot east of 98L would be in the tropical wave where clear development would again be striking.
-- -- development in Bay of Campeche or Western Gulf (NW of 96L).
-- Simultaneous movement of the system of storms. For example the SW storm could move across Panama into the Pacific to setup a larger TC. In this case, a linked system could rotate to follow the moving center while maintaining its relative spacing: 97L moves to mid-Caribbean and 98L slides NW up the SA coast.
-- Relation of development to spacing. With the cross Panama and expand idea, perhaps all three storms would take a concurrent step outwards from the center of the triangle maintaining a similar spacing with the same proportion (side:base) and larger vertices. 97L moves just N of Caribbean (or stays put and develops N) while 98L backs to the ESE into the tropical zone.
-- Interactions of each affect the whole. For example, on TC is suddenly sheared & has reduced outflow. All of the other TCs then immediately show related changes of inflow, outflow &/or development.
I have given more than four possible spots for additional TC development if this pattern is actually a higher-order response of the trpoical Atlantic. If three or more occur today (7/5) then I think it highly likely that this pattern of storms is a system that expresses a higher-order + higher energy response of the atmosphere and ocean. Additionally, it is likely there are many other possible developments besides the ones I give that would demonstrate that this pattern is actually a linked system of TCs.
To go one step further, I think that the demonstration of this pattern as a higher-order response would show that global warming (more energy in the atmosphere) is causing emergent phenomena in tropical weather. It is true that when more energy is in a system, higher order/energy responses become more possible and more likely to occur. We may learn over the next day or two if we face a new kind of tropical storm system: a persistent &/or self-regenerating distributed system of TCs.
Perhaps it is a subtropical replication of the tropical wave to cool more ocean faster. For the same amount of cooling the system approach maybe preferable to large TCs as long as the system's TCs don't grow large. If the TCs within a system establish and grow in place to dominate the tropical weather then the bright side is that when it is done raining just about the whole ocean will be too cool for TCs or, at least, have a negative temperature anomaly.
There are three here now, then there is a massive tropical wave which will quite likely be followed by one extra large storm. Please note that there are more than just a few TCs developing at once here: with what is in the box now, this season is poised to take way some of 2005's records. Plus there is no very dry and dusty SAL west of 10W - both the African monsoon and the wraparound moisture from Debby have cooperated to bottle up the SAL in the Sahara and weaken or suppress it just about everywhere outside the Sahara. The jet is swinging across to apply another push back to the SAL. With TCs surfing on the dread westerlies and the way made juicy for east Atlantic storms ... it is on!
On Sunday, I predicted three named storms this week (thru Sun 7/9)... Ooops!!!
It seems much less risky to now predict that in the Atlantic basin thru 7/9 three named storms will form and two will become hurricanes (one major) at some point in their lives. It sure looks like it could get a whole lot worse.
PS: I may have misnamed the storms but here is the convention I followed above:
96L - the TC forming in the Bay of Nicaragua/Panama/Columbia
97L - the TC growing just E of Puerto Rico
98L - the TC growing in the northern band of tropical moisture just below 10N and just off the South American coast.
PPS: -- at 1015 UTC 0705 the original 97L piled up an rode up on a crest in the westerly shear band and one can expect that later, as this change in the westerly moves down the band that 98L will move away from the coast. 98L will live on the west edge of the westerlies and generally move NE or stall. Do not expect 98L to hopelessly ground itself and disperse thereby (Although the weakened SAL might still wear 98L down.) Also it does appear now at 1245 UTC that the westerlies are getting soggy and losing power.
PPPS: A bit surprised that there is no mention of any of this in the 8AM Atl Fcst Disc. And the cross Panama move appears to be starting .. we will see about all this soon enough.