Well, what a difference a day makes! If you've been following along the past couple days, I've been describing the rapid formation of Tropical Storm Cosme from an very un-impressive and rather disorganized wave in the ITCZ 48 hours ago, up to the point before being upgraded to Tropical Storm status and named 'Cosme'.
First, the depression was upgraded to tropical storm at 11am Sunday HST, just hours after my last post (see above), just I was expected it would be.
... additionally, a new tight band is now forming in the NW quad, closer and tighter to the center of this developing storm, all the while the strong thunderstorm very near the LLC is building, pulsing and expanding, too ... if this trend continues, I can well imagine a CDO (Central Dense Overcast) feature developing over the LLC later today, which tends to foster further intensification ... sure looks like Tropical Storm status is imminent. If this does occur, it will be named "Cosme".
Unlike Saturday afternoon (Hawaii time), when the inner core convection entirely dissipated, leaving only modest convection in a sort of distant 'ring' well removed from the center, today (Sunday - yes it's still Sunday Hawaii time as I write this) the story is quite different.
Interestingly, totally opposite of yesterday, the banding convection died away entirely during the 'diurnal minimum' (see above post for clarification) during the daylight hours, leaving *only* a 'ball' of deep convection persisting under a CDO-like feature. But this inner-core, pulsating convection remained very intense, with cloud top temps of -80 or colder. From the NHC's 11 am discussion:
"THE SATELLITE PRESENTATION OF THE CYCLONE HAS CONTINUED TO IMPROVE TODAY. THE ONCE BROAD CIRCULATION HAS BECOME MORE CONSOLIDATED AND THE CENTER IS EMBEDDED UNDER THE DEEP CONVECTION ... BASED ON THESE DATA SIX-E HAS BEEN UPGRADED TO TROPICAL STORM COSME"
... and, in the next advisory, 5pm HST ...
"COSME IS GETTING BETTER ORGANIZED. AN AMSR-E OVERPASS AT 2200 UTC SUGGESTED THE DEVELOPMENT OF A TIGHTER INNER CORE...AND SUBSEQUENT CONVENTIONAL IMAGERY SHOWS A SIGNIFICANT INCREASE IN CONVECTION NEAR THE CENTER ... IT SHOULD BE NOTED THAT COSME IS EMBEDDED IN A LARGE CYCLONIC GYRE THAT INCLUDES THE REMAINS OF TROPICAL DEPRESSION 5-E...AND THIS MAY PRODUCE SOME TRACK WOBBLES ..."
... and with regard to forecasted intensification ...
"COSME IS IN AN ENVIRONMENT OF LIGHT SOUTHEASTERLY VERTICAL SHEAR... AND THE CYCLONE SHOULD REMAIN IN A FAVORABLE SHEAR ENVIRONMENT FOR AT LEAST THE NEXT FOUR DAYS. THUS...THE INTENSITY WILL BE CONTROLLED MAINLY BY THE SEA SURFACE TEMPERATURES ... SHIPS FORECAST COSME TO BECOME A HURRICANE ...THERE IS A CHANCE COSME COULD BECOME A HURRICANE." (much of this discussion was edited; see NHC's website for details).
In fact, if you take a quick peek at the provided attachment, taken at 7pm Hawaii time (from the F16 polar orbiting satellite's passive microwave sensor, which shows the deep, convective features *through* the obscuring cirrus debris and the persistant CDO feature over the LLC) you can notice that the inner core convection, in addition to becoming noticebly more tightened, has actually "closed off " into a nascent eyewall formation.
Remember, this was just a very 'blah', non-descript tropical wave embedded in the ITCZ only a mere 48 hours ago! Can you say 'rapid cyclogenesis' ?
And now as I write , and as we again enter the 'diurnal convective max' in this basin, the inner core convection, after doing more than just 'holding it own' during the daylight hours, is really beginning to wind ever tighter under the persistent CDO-like feature.
Ah! The latest advisory (11pm Sunday Hawaii, 5am Monday Florida) has just come out. Here we go ...
"COSME HAS CONTINUED TO STRENGTHEN EARLY THIS MORNING. MICROWAVE OVERPASSES DURING THE PAST SEVERAL HOURS SHOW THAT THE CYCLONE HAS EXCELLENT BANDING FEATURES AND THE BEGINNING OF AN EYE ... SINCE COSME IS FORECAST TO REMAIN IN A LOW SHEAR ENVIRONMENT FOR THE NEXT SEVERAL DAYS THE MAIN FACTOR CONTROLLING INTENSITY WILL BE SEA SURFACE TEMPERATURES ... GIVEN THE CURRENT STRENGTHENING TREND...THE INTENSITY FORECAST WILL FOLLOW THE SHIPS MODEL CLOSELY AND PREDICT A HURRICANE WITHIN 24 HOURS."
Hmmm.... Interesting. While this system was still in it's formative, depression stages, NHC was calling for a peak intensity of just 45 Kts. But I've always had an "intuition" that this system was going to exceed those predictions, even possibly making it to minimal hurricane status. Now, it seems that my earlier intuition is proving to be correct.
If Cosme does make it to hurricane, it will be the *first* hurricane anywhere in the Northern Hemisphere 2007 season.
Which is quite suprising to me, as there is usually a hurricane in the EastPac basin closer to Mexico, by late May or certainly sometime in June. But here we are mid-July and NO Hurricanes ANYWHERE yet! (Typhoons and Powerful Tropical Cyclone Gonu in the Arabian Sea not-withstanding.)
Just for 'continuity' sake, the 'binary interaction' between Cosme and TD-5E that I speculated about in my previous post never occured. Apparently, the depression was too small and too weak for this effect to take place. But Cosme is doing well enough on its' own, and didn't need to be 'nudged' toward the SW, over still warmer SST's, for what is looking to be intensification into a hurricane, anyways.
Latest 6-hour IR loop from the UH weather server:
Finally, all this is certainly not going unnoticed by the NWS here in Honolulu (co-located with the CPHC, Central Pacific Hurricane Center, and manned by the same excellent meteorologists), as they are beginning to make mention of it in their long-range synoptic forecast discussion:
"BY -NEXT- WEEKEND...THE MODELS PREDICT THE DISSIPATED REMNANTS OF
(Cosme) TO APPROACH THE MAIN HAWAIIAN ISLANDS ... LEADING TO SEVERAL STILL AND MUGGY DAYS. (ala: dewpoints in the low to mid 70's)
RAINFALL WILL BE ANOTHER MATTER ENTIRELY...SINCE AS LONG AS THE MODELS CONTINUE TO SHOW THIS FEATURE MOVING INTO THE VICINITY OF THE STATE ... THE PLENTIFUL ATMOSPHERIC MOISTURE ASSOCIATED WITH THE LOW MAY WELL ENCOURAGE LOCALLY HEAVY DOWNPOURS."
Looks like Cosme just might have a few more tricks up her sleeve, before all is said and done. Will keep you 'posted', pun intended.
Latest developments before I logout.
3am Hawaii time, 9am Florida time:
Cosme just keeps getting more organized by the hour. NRL bumped up the winds to 50 Kts at 9pm HST while dropping the pressure to 997 mb, and the NHC, in their latest 11pm HST advisory, increased the winds again to 55 Kts., just 2 hours later.
And outer convective banding features, essentially absent during the daylight hours, are now again forming tightly curved bands contracting towards the center, all the while the inner convection is contracting and tightening too, and these inner-core thunderstorms remain quite deep and cold.
I believe we are seeing a sort of 'psudo-eyewall replacement cycle' (remember the microwave satellite clearly showed a nascent eyewall feature developing as early as 7pm HST), and within the next 12 to 18 hours we'll be seeing a bonafide eyewall and an upgrade to "Hurricane Cosme".
So much for the " ... development of this system .. if any .. will be slow to occur ..." from NHC's outlook on just another 'ho-hum' wave, just a scant 48 hours ago.
It indicates, too, that we still don't have that great a handle, in some cases, on all the factors that lead up to rapid tropical cyclongenesis or 'explosive intensification' like Andrew and Charley.
"Don't Get Stuck on Stupid" - General Honore, following Hurricane Katrina
Edited by CoconutCandy (Mon Jul 16 2007 09:27 AM)