The Invest 90E that the NHC has been monitoring for several days has organized and strengthened sufficiently to become the first named tropical storm of the Northern Hemisphere 2010 Hurricane Season.

Overnight convection was sufficiently deep and sustained enough near the rapidly developing circulation center embedded within a broad 1005 mb area of low pressure and formed a small Central Dense Overcast (CDO) feature, evident on animated satellite imagery and usually the harbinger of a deepening phase in storm dynamics. Also clearly in evidence in more recent daylight imagery is a nicely established outflow, especially in the NW semicircle, where the cirrus outflow debris is assuming the classic 'feathery pattern', another feature I've noticed that frequently coincides with an organizing and deepening trend, from depression to storm or storm to hurricane, for example.

And very deep, bursting and continuously cycling convection continues unabated at this hour, despite midday being the so-called 'diurnal convective minimum', when thunderstorm activity generally subsides to some extent. Should current convective trends continue, there is a chance 'Agatha' could strengthen substantially more than is currently forecast. In fact, SHIPS Rapid Intensification Model now suggests at least a 40% probability of 'explosive intensification' (rapid deepening) of 'Agatha' over the next 24 hours.

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SINCE AGATHA WILL BE MOVING SLOWLY OVER VERY WARM SSTS OF AT LEAST 30C AND WITHIN A REGION OF LOW VERTICAL WIND SHEAR ... ADDITIONAL STRENGTHENING SEEMS REASONABLE. THE SHIPS MODEL IS INDICATING A NEAR 40 PERCENT CHANCE OF RAPID STRENGTHENING DURING THE NEXT 24 HOURS ... AND THIS POSSIBILITY WILL BE CLOSELY ASSESSED FOR THE NEXT FORECAST PACKAGE IF THE RECENT CONVECTIVE DEVELOPMENT TREND CONTINUES INTO THE AFTERNOON HOURS WHEN THUNDERSTORM ACTIVITY OFTENTIMES WEAKENS.
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Also of significant interest is the fact that this marks the 10th year of the last 11 (missing only in 2009) when a Pacific tropical cyclone formed in the month of May, which is the most (nearly) consecutive years in which storms formed in the month of May, perhaps a reflection of the multi-decadal increase in tropical cyclone activity we've seen, beginning in 1995.

The last storm to form in the EastPac during the month of May was Tropical Storm 'Alma' in 2008, which holds the all time record for developing further east than any other Pacific tropical cyclone on record. (Also, 'Alma' made landfall further east than any other Pacific tropical cyclone, and remains the ONLY storm to do so on the *Pacific Coast* of Nicaragua.)

Tropical Storm ALMA in 2008

It should be remembered, too, that it was partially the remnants (remnant mid-level circulation?) of the dissipated 'Alma' (name since retired) that crossed into the Atlantic basin that gave rise to an early season Tropical Storm 'Authur' in 2008, just a scant 2 years ago. 'Alma' is the most recent former Eastern Pacific tropical cyclone to in any sense "cross into" the Atlantic basin.

Tropical Storm ARTHUR also in 2008

Quite interestingly, despite the official NHC forecast to dissipate 'Agatha' inland over Mexico in 3 days or so, the model guidance remains quite bullish and increasingly in consensus in bringing the remnant, perhaps mid-level, circulation into the Atlantic basin on a trajectory towards southern Florida or even into the GOM. Let's hope there is NO early season storm in the Gulf, which would greatly exacerbate the already terrible situation with the BP oil spill.

Note in the above graphic that several of the models are the 'outsiders', notably the GFDL (blue), which meanders the system in a tight cyclonic loop just offshore, without making any landfall at all for the duration of it's model run, and the GFS (red), which likewise has it remaining largely offshore on a lethargic northward course, bringing it to landfall very late in the forecast period.

Finally (for now) it's worth noting that on this day in 2001, Major Hurricane Adolph maxed out as a strong Category 4 Hurricane with 145 mph sustained winds, making it the strongest May Eastern Pacific hurricane on record.