CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Edit Note:
The disturbance I thought would become 'TD-5E' has been designated 'TD-6E', instead. Apologies for any confusion. Please see the replies to this post for a follow-on as to what's happening with these 2 depressions. - Norm
-----------------------------------------------------------
I'm sure we've all read a that says "development of this system ... if any ... will be slow to occur".
Such was the expected case, just 6 hours ago, with a tropical wave in the EastPac, out near 125W.
But, in just that short time, there have been several, large bursts of deep convection (as cold as -90!) near the LLC of a weak low embedded in the wave.
And, because of this, the wave has gone from rather 'disorganized' to VERY organized, in that brief period, or so it certainly appears from the IR loop.
Additionally, there is a very conspicuous banding feature in the SE quadrant, with numerous thunderstorms with temps as cold as -80, assuming a distinctive 'wrapping' feature which is continuing to grow (as I write this, 2am Hawaii time, 8am Florida time) which is close enough to the LCC to aid in dropping surface pressures even further.
SST's are plenty warm, and the general thermodynamic environment (quick check of the water vapor loop) seems to be rather favorable, as well, at least in the short term.
I've been watching systems 'spin up' for many years, and this is among the *fastest* I've ever seen, in going from just another 'ho-hum' wave embedded in the , into something that sure looks like it's well on it's way to becoming a TD, if it isn't already a depression.
It certainly looks very "depression-ish", and IMHO, will probably begin issuing advisories sometime later today. They're likely waiting on the visible loops and an upcoming QuikScat pass to make an assessment on this system.
Another disturbed area to the NE of this one, although smaller and over somewhat cooler water, also has the potential to become a depression later today, or at least according 's issued at 11Z, before encountering SST's too cool for significant development later on Sunday.
But this 'wave' near 125W sure looks 'promising' for the next tropical storm. Time will tell.
It sure spun up quickly in just 6 hours. Just goes to show, not the disparage the good folks at the , that we sometimes don't have that great a handle on the all the factors leading to rapid cyclogenesis.
Have a look at this time loop, which goes from 'blah' to 'interesting', and you'll see what I mean : (See note below)
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
(PLEASE NOTE: Time 'Expired' 12-hour IR loop from UH's weather server. This link only shows the *most recent* 12 hours of loop, and no longer shows you the 'rapid cyclogenesis' I was describing above, but will show you, instead, this area of the EastPac basin through the day on Sunday, or whatever day you happen to be reading this post. Will research into how to 'preserve' the time segment 'of interest' for future postings.)
(I like to click the 'Rock' button, for a forward / backward loop, which helps to more clearly visualize convective trends.)
Warm Aloha from Hawaii - Norm
Edited by CoconutCandy (Mon Jul 16 2007 08:17 AM)
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Just a quick update on what's happening to the 'Dual Depressions' in the East Pacific.
I'll paraphrase bits and snips of 's current and previous Forecast Discussions, relevant to this post, for those not inclined to read the discussions on the website, especially just for a 'sniggling' little depression in the Eastern Pacific. 's discussions are "quotated" and in ALL CAPS.
TD-5E, it seems, is already encountering cooler SST's and may never quite make it to storm status, just I suspected 24 hours ago with my first post. (See above.)
Per 's latest advisory (NUMBER 4 - 200 AM PDT SUN JUL 15 2007) (paraphrased)
" ... THE DEPRESSION CONTINUES TO STRUGGLE THIS MORNING ... THE SYSTEM BARELY CLASSIFIES AS A TROPICAL CYCLONE ... (a recent) QUIKSCAT PASS INDICATES THAT THE CIRCULATION IS QUITE SMALL AND THAT THE MAXIMUM WINDS ARE NO HIGHER THAN ABOUT 25 KT.
THE ENVIRONMENT AHEAD OF THE DEPRESSION IS RATHER HOSTILE WITH STRONG SHEAR AND COOLER SEA SURFACE TEMPERATURES ...
SEVERAL OF THE GLOBAL MODELS SUGGEST THAT THE REMNANT LOW COULD BE ABSORBED BY THE LARGER CIRCULATION OF TROPICAL DEPRESSION SIX-E DURING THE NEXT 2-3 DAYS."
Hmmm .... That last statement is rather interesting, and I will come back to it in my next post. (See below.)
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Please note: The following post is a bit long, but I've tried to keep it 'lite' and interesting, perhaps even entertaining, and especially slated for newcomers and those interested in learning more about the tropical storm formation process. All due apologies to the 'Mets'. And, because the Atlantic / Caribbean is *so* quiet, this might be of more interest for more people than would otherwise be the case. Enjoy!
------------------------------------------
Meanwhile! TD-6E is looking *much* more interesting this morning; an altogether different story.
Convection decreased dramatically during the day on Saturday, as is often the case with formative systems during daylight hours, leaving no deep convection near the LLC and with only modest convection, at best, in a sort of ring, well away from the center.
From the 's #3 discussion - 800 PM PDT SAT JUL 14 2007 (paraphrased)
"THE DEPRESSION CONSISTS OF A LARGE CIRCULATION DEFINED BY A FEW
CYCLONICALLY CURVED CONVECTIVE BANDS...BUT IT LACKS A CONVECTIVE
INNER CORE ... THE DEPRESSION IS STILL IN ITS FORMATIVE STAGE...WITH CLOUD SWIRLS ROTATING AROUND A HARD TO DISCERN CENTER OF CIRCULATION AS THE CONVECTION CONSOLIDATES AND THE CIRCULATION BECOMES BETTER DEFINED.
THE ENVIRONMENT OF THE CYCLONE IS GENERALLY FAVORABLE FOR DEVELOPMENT...WITH DIVERGENCE ALOFT...LIGHT SHEAR...AND WARM WATERS. HOWEVER...THE CIRCULATION IS STILL ENGAGED WITH THE AND THE CONVECTION IS WIDELY DISPERSED. THIS WOULD ARGUE AGAINST RAPID DEVELOPMENT... ALTHOUGH INTERESTINGLY ENOUGH THE SHIPS RI INDEX IS VERY HIGH."
And the #4 discussion, issued 6 hours later at 11pm Hawaii time, the most recent as I write this, pretty much maintains the same scenario:
"THE DEPRESSION CONSISTS OF A LARGE CIRCULATION DEFINED BY A
FEW BANDING FEATURES AND LITTLE CONVECTION NEAR THE CENTER. AN
ENVIRONMENT OF LOW SHEAR AND WARM OCEAN WOULD FAVOR SOME
STRENGTHENING DURING THE NEXT DAY OR .
And then, around Midnight Hawaii time, a deep burst finally did develop near or over the LLC of the depression, totally in line with the 'diurnal convective max', when dewpoints are highest (higher humidity) and 'radiative cooling' at the top of the atmosphere is also highest, which causes strong thunderstorms to more easily develop, for those not familiar with this 'diurnal' (daily) process.
And what was only modest convective banding in the SE and W 'quads' just prior to discussion #4 issuance, rapidly evolved into strong, deep convection, with temps of -80 or colder (very strong thunderstorms!) and spread and wrapped and merged into a well organized band in the SE semi-circle, while drawing ever closer to the LLC center.
To help you visualize this better, please visit the excellent University of Hawaii weather server's IR satellite loop for the past 12 hours. Open in a new window (or tab) and read on!
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
(Remember to click 'Rock', if you desire a forward / backward looping effect.)
In this animated loop, you can also notice a very pronounced strong southerly surge of very moist, cross-equatorial flow between 115W and all the way to the storm itself, pumping in huge amounts of very warm, moist tropical air which fuels the deep thunderstorms and provides a very favorable 'thermodynamic' environment for the storm to grow and thrive.
(PLEASE NOTE: This is now a 'Time Expired' 12-hour IR loop from UH's weather server, and no longer illustrates exactly what I was describing above. This link only shows the *most recent* 12 hours of loop. Will research into how to 'preserve' the time segment 'of interest' for future postings.)
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 (Central Dense Overcast) feature developing over the LLC later today, which tends to foster further intensification (correct me if I'm wrong, Mets).
And, finally (whew!), in the last few frames of the animated IR loop, (as I write this 5am Hawaii time, 11am Florida time), an even tighter convective band is forming, even closer to the center, and the central 'ball' of convection is flaring up again, with temps -85 or colder, and the overall banding drawing ever closer and more 'tightly wound'. Sure looks like Tropical Storm status is imminent. If this does occur, it will be named "Cosme".
Perhaps most interesting of all, is that there now appears to be some 'binary interaction' beginning to occur between fizzling TD-5E to the NE, and this much larger, much more organized system. One can see in the last few frames from the animated IR loop (link provided above) that the remaining deep convection from TD-5E is making a 'bee-line' towards TD-6E, apparently being drawn in towards the much larger circulation.
I'll speculate on possible 'binary interaction scenarios' in my next post, later today sometime. And I'm sure we'll get 's 'take' on this in their next advisory, as well.
Finally, I've attached (click attachment at top of the post) a nice QuikScat satellite image of TD-6E, taken around 4pm Hawaii time (10pm Florida time), Saturday, which shows, quite nicely, the surge of very moist air I mentioned earlier, flowing into the storm from the south and you can very well see, too, that the banding feature in the SE quad (the strongest 'moderate' thunderstorms at picture time, before the deepening trends in the overnight hours) contains the strongest winds, associated with the deepest convection. Ah, QuikScat, how I've come to love you!
Apologies, again, to some of you, for this rather long-ish post. But, since there's nothing really of interest currently in the Atlantic basin, I thought I'd share with you this rather interesting cyclogenesis process in the Eastern Pacific and what could become even more interesting if significant strengthening does happen and the 'binary' interaction with TD-5E does occur over the next few days. We shall see! More later.
Edited by CoconutCandy (Sun Jul 15 2007 09:57 PM)
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
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 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.
Quote:
... 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 (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 -like feature. But this inner-core, pulsating convection remained very intense, with cloud top temps of -80 or colder. From the '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 '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 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 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 -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, 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:
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
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. bumped up the winds to 50 Kts at 9pm HST while dropping the pressure to 997 mb, and the , 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 '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 .
--------------------
"Don't Get Stuck on Stupid" - General Honore, following Hurricane Katrina
Edited by CoconutCandy (Mon Jul 16 2007 09:27 AM)
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Tropical Storm Cosme was upgraded to Hurricane at 11am HST, after steadily strengthening overnight and during the morning hours.
From 's latest (11am HST) forecast discussion:
"THE SATELLITE PRESENTATION HAS IMPROVED AND COSME HAS A SMALL EYE WITH A WELL-DEFINED CURVED BAND WRAPPING FULLY AROUND THE CENTER. ESTIMATES FROM BOTH AND SAB ARE 65 KT. THE INITIAL INTENSITY HAS BEEN RAISED TO 65 KT."
The 'pseudo-eyewall replacement cycle' discussed in my last post did occur, and for a few hours a small eye was observed on visible satellite imagery. Since then, the eye has become cloud filled and/or obscured by cirrus debris.
However, IR imagery continues to show deep convection forming near the center, so it is difficult to say whether Cosme has peaked in intensity or is still strengthening just a tad more, per 's forecast peak of 70 Kts. And it continues to exhibit excellent outflow in nearly all quadrants, with very light shear prevailing for the foreseeable future.
The next advisory in a couple hours will reveal Cosmes' strength following the visible eye event. I suspect it is still maintaining a closed eyewall feature, shown nicely in a TRMM microwave overpass at 9:30 this morning HST. (See attachment.)
If Cosme hasn't peaked yet, it is expected to do so soon. From visible satellite loops it's apparent that Cosmes' circulation is beginning to entrain more and more of the stable stratocumulus cloud field to its NW.
More importantly, the projected track will take Cosme over progressively cooler SST temps in the next 24-36 hours. It will be crossing over several isotherms in quick succession during that time frame, as the thermal gradient is rather tight in this area.
"...COSME'S INTENSITY COULD BE PEAKING...SINCE WATER TEMPERATURES ARE
ALREADY BELOW 26C AND ARE EXPECTED TO DECREASE FURTHER ALONG THE
PROJECTED TRACK. THE OFFICIAL INTENSITY FORECAST ALLOWS FOR SOME
STRENGTHENING IN THE NEXT 12 HOURS...BUT THEN GRADUALLY WEAKENS THE
CYCLONE THROUGH DAY FIVE...AS A RESULT OF THE COOLER WATERS AND A
MORE STABLE ENVIRONMENT."
The good / bad news, depending on your perspective, is that Cosme is now expected to maintain its' identity longer than earlier forecast, and the latest track shows a minimal tropical storm with its' center of circulation passing over or just barely south of the southern tip of the Big Island of Hawaii in the early morning hours this Saturday.
[image] http://www.nhc.noaa.gov/refresh/graphics_ep1+shtml/203532.shtml?5day?large#contents [/image]
(In case the above image doesn't display, here's the direct link:)
http://www.nhc.noaa.gov/refresh/graphics_ep1+shtml/203532.shtml?5day?large#contents
While it is very likely that Cosme will bring much-needed rains to the Big island and perhaps Maui, it will also bring in tons of humidity over the state as it passes by during the weekend, making for several days of very muggy and highly uncomfortable weather.
Let's just hope it does weaken as quickly as expected; while the Big Island certainly needs a good soaking, it surely doesn't need any kind of severe wind event to contend with. 
And as I was mentioning in my previous post ... and from 's last discussion ...
"ONE BIT OF TRIVIA...ONLY FOUR OTHER EAST PACIFIC HURRICANE SEASONS
HAVE HAD THEIR FIRST HURRICANE FORM LATER THAN COSME."
... and the fact that Cosme is the first *hurricane* to form in the Northern Hemisphere 2007 season. Rather unusual.
More coming after the 5pm HST advisory from the ...
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Cosme lasted as a hurricane for 2 advisories, and has now been downgraded to a TS as of 11pm HST.
"MICROWAVE PASSES OVER THE PAST SEVERAL HOURS SHOW THAT THE LOW-LEVEL CENTER OF COSME IS LAGGING BEHIND ITS DEEP CONVECTION ... THE QUIKSCAT DATA ALSO INDICATED THAT COSME HAD WEAKENED TO A TROPICAL STORM."
(I've attached a rather nice QuikScat image while Cosme was still a hurricane. It is a *complete* pass over the cyclone, and shows very well how the strongest winds are associated with the deepest convection. Certainly worth a look.)
Although the hurricane force winds covered only a small area, the overall circulation of Cosme remains quite large, nearly 200 miles. So it may take a while for the cyclone to spin down.
Some easterly shear and progressively cooler SST's will take their toll over the next few days, however it's still on a projected track that may bring it as a minimal tropical storm very near or over the Hawaiian Islands this weekend. And as Cosme nears Hawaiian waters the SST's will gradually become somewhat warmer again.
"EASTERLY SHEAR AND COOL WATERS SHOULD CAUSE COSME TO CONTINUE TO WEAKEN OVER THE NEXT COUPLE OF DAYS. AFTER THAT...THE SHEAR IS FORECAST TO WEAKEN ... AND TOWARDS THE END OF THE PERIOD SST'S ALONG THE TRACK WILL INCREASE AGAIN. CONSEQUENTLY...IT'S AT LEAST POSSIBLE THAT COSME COULD MAINTAIN TROPICAL STORM STRENGTH THROUGH THE FORECAST PERIOD."
This might be interesting, due to the large size of the circulation and it's forecasted maintaining TS strength. The Islands may be in store for a rather wet, blustery weekend. We shall see if this pans out.
More tomorrow ...
- Aloha from Honolulu
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Cosme weakened rather dramatically overnight, from 60 Kts. down to 40 Kts.
From the 11pm Monday (HST) discussion:
"MICROWAVE PASSES OVER THE PAST SEVERAL HOURS SHOW THAT THE LOW-LEVEL CENTER OF COSME IS LAGGING BEHIND ITS DEEP CONVECTION ... AS COSME MOVES OVER INCREASINGLY COOLER WATERS IT WILL HAVE A MORE DIFFICULT TIME RESPONDING TO THE UPPER-LEVEL EASTERLIES ... MODEL GUIDANCE IS IN PRETTY GOOD AGREEMENT ON BRINGING COSME NEAR OR OVER THE HAWAIIAN ISLANDS IN 4-5 DAYS."
And from the next (5am HST) discussion:
"DURING THE LAST SIX HOURS...BOTH MICROWAVE AND CONVENTIONAL
SATELLITE IMAGERY INDICATE THAT THE CLOUD PATTERN HAS QUICKLY
DETERIORATED. TRMM AND AMSR-E OVERPASSES FROM 1018 UTC AND 1056
UTC RESPECTIVELY SHOW THAT THE LOW-LEVEL CENTER IS EXPOSED WITH THE
REMAINING DEEP CONVECTION LOCATED ABOUT 60-75 N MI TO THE WEST."
And, with the first visible images of the day, it was lowered to 35 Kts., a minimal tropical storm. As mentioned, the LLC was entirely exposed with a tight, low cloud swirl around a large clear "eye"-like feature. Apparently the cooler SST's and, especially, the easterly shear had really taken their toll.
"BOTH COOL WATERS AND EASTERLY SHEAR ARE ANTICIPATED TO CONTINUE TO
INFLUENCE THE CYCLONE'S INTENSITY...THE OFFICIAL INTENSITY FORECAST MAINTAINS COSME AS A WEAK TROPICAL STORM THROUGH 4 DAYS. HOWEVER IF THE CURRENT RAPID WEAKENING TREND CONTINUES...SOME ADDITIONAL DOWNWARD ADJUSTMENTS WILL NEED TO BE MADE."
And the latest (11am HST) discussion ...
"THE VISIBLE SATELLITE IMAGERY SHOWS THAT COSME HAS AN EXPOSED
TIGHTLY-SWIRLED CIRCULATION WITH A FEW THUNDERSTORMS CONFINED TO
THE SOUTHWESTERN QUADRANT OF THE CYCLONE ... COSME REMAINS OVER 25C WATERS AND UNDER THE INFLUENCE OF EASTERLY SHEAR ... IF THE CYCLONE SURVIVES THE NEXT THREE DAYS AND STAYS SOUTH OF THE FORECAST TRACK...THE WATERS WARM BACK UP WHICH COULD ALLOW FOR REGENERATION."
And is now forecasting a downgrade to depression status by the next advisory, and holding Cosme as a depression through the forecast period.
However! In the last few frames of the animated IR loop, very deep convection, with temps of -80 and colder, has once again flared in the SW quadrant, is building and is now over-spreading the LLC. Unusual for the diurnal convective minimum of the daylight hours. (It is now early afternoon, Hawaii time, don't forget: 1pm HST, 7pm EDT)
If this convective trend continues, I hazzard to speculate that Cosme will NOT be downgraded to Depression, as forecast, but may well hold it's TS strength a while longer.
Perhaps the easterly shear is relaxing just a tad, and allowing for deep convection to re-form near and over the LLC. At any rate, it certainly will be an uphill struggle, in view of the cooler SST's mentioned above, at least in the short term.
However, as Cosme enters Hawaiian water later in the forecast period, with progressively warmer SST's, like the discussion says, some regeneration and intensification is not out of the question. Time will tell.
Here's the link to the latest IR loop. Have a look for yourself.
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
Will keep you posted. - Norm
|
Clark
Meteorologist
Reged:
Posts: 1710
Loc:
|
|
I was kinda surprised to see the flareup of convection again this afternoon, given the relative low-level stability over the cooler SSTs. It'll be critical to the storm's survival to see that convection persist, even in a sheared state.
From anecdotal experience, it seems like most storms that track in this direction toward Hawaii do not make it as coherent tropical cyclones. There was one a year or three back -- the J storm, I want to say -- that tried by was reduced to a low-level cloud swirl before it reached the state. The waters seem to be *just* cool enough -- and occasionally coupled with one other negative factor -- to weaken these storms to the point of prohibiting regeneration further west. But, given that the chance is there, it's still prudent to mention it, as the has done and is doing.
Will be interesting to see what ultimately happens...
--------------------
Current Tropical Model Output Plots
(or view them on the main page for any active Atlantic storms!)
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Cosme continues to fire off pulsing deep convection in the SW quadrant. It's quite apparent that the easterly shear is trying to knock it down, and may yet suceed in doing just that over the next day or two.
NHC's 11pm HST discussion, highly paraphrased:
"COSME CONTINUES TO MAINTAIN DEEP CONVECTION IN THE SOUTHWESTERN QUADRANT OF ITS CIRCULATION AS IT MOVES OVER 25C WATERS ...
COSME IS MAINTAINING A RESPECTABLE AMOUNT OF CONVECTION GIVEN THE SST'S IT IS CURRENTLY TRAVERSING. EVEN COOLER WATERS LIE AHEAD ...HOWEVER... AND REACH A MINIMUM BEFORE THE SHEAR IS EXPECTED TO DIMINISH IN ABOUT 48 HOURS. AS A RESULT...THE OFFICIAL FORECAST CALLS FOR COSME TO WEAKEN TO A DEPRESSION BY THIS TIME TOMORROW.
But Cosme may still have 'a few tricks up her sleeve', so to speak:
"AFTER THAT...SST'S ALONG THE TRACK WILL BE INCREASING...AND THERE COULD BE SOME REGENERATION BY 72 HOURS. NONE OF THE EXPLICIT INTENSITY GUIDANCE...INCLUDING SHIPS...NOW SHOWS ANY DECAY AT THE END OF THE FORECAST PERIOD."
Just as I suspected in my last post, when was ready to give up on Cosme, weaken it to a depression, and then dissipate it entirely. Now they are expressing a change in their thinking, due to the tenacious convective flareups.
In fact, 's intensity forecasts have been, for the most part, too conservative pretty much all along. Showing, again, that we don't always have the greatest handle on all the factors relating to intensity fluxuations.
As an aside, it should be noted that Cosme is about to cross over 140W, when in Miami will issue their last advisory, and the CPHC (Central Pacific Hurricane Center), here in Honolulu, now located on the University of Hawaii at Manoa campus, will take over forecast responsibilities, until the system dissipates or moves west of the dateline, 180W.
So, later today (Wednesday), please visit ...
http://www.prh.noaa.gov/cphc/
... for the latest advisories on Cosme as it traverses the Central Pacific Basin and nears the Hawaiian Islands.
Latest 12 hour IR loop:
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
Any thoughts on all this? Please feel free to add to the thread with your ideas and observations!
|
Clark
Meteorologist
Reged:
Posts: 1710
Loc:
|
|
Cosme's trying to hang in there tonight, but only just so, making me hesitant to want to either write it off or proclaim it a minor threat. Convection went on the wane again this afternoon but is now trying to refire in the southeastern quadrant of the storm, probably closest to the warmest and most unstable air at the surface. Conditions do improve as it gets further west -- SSTs warm, low level stability goes down -- but as the has hinted at, southwesterly shear starts to play a role as it nears and passes Hawaii.
Of course, that's also one of the most data sparse regions in the N. Hemisphere and I'm not sure how much to trust forecasts of subtropical upper lows at 4-5 day lead times, so I think we have to take it with a grain of salt for now. Of course, I could also be suffering from a tad bit of Ioke memories, as I remember the forecasts that had it succumbing to shear and/or recurving at about 160-170W, so bear with me if so!
I don't see why, given what it has done the past two days, it can't at least maintain itself for another couple of days in this fashion. I'd say it has a brief window for modest restrengthening as it passes south of Hawaii -- assuming it holds together -- and then, as of now, will likely end up in a hostile environment that may ultimately bring about its demise. Still, if my memory serves me right, this would be the rare storm to make it near Hawaii on this trajectory as something more than a low cloud swirl; the storms that generally make it to this longitude are further south.
--------------------
Current Tropical Model Output Plots
(or view them on the main page for any active Atlantic storms!)
|
RevUp
Weather Guru
Reged:
Posts: 181
Loc:
|
|
Very interesting discussion about our first hurricane of 2007 in the western (N) hemisphere. Pretty amazing storm to still be generating such strong convection at it's center. I agree that model data needs to be viewed with some uncertainty due to location, lack of data and limited synoptic climatology. Would not be surprised to see the remnants of COSME re-strengthen to TS as it nears the islands. Thanks for sharing your insights.
--------------------
"Let tomorrow worry about itself. Each day has enough trouble of its own."
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Cosme has crossed over 140W and the in Miami has handed over responsibility to the Central Pacific Hurricane Center (CPHC) in Honolulu.
http://www.prh.noaa.gov/cphc/tcpages/COSME.php
Meanwhile, Cosme has been downgraded to Depression status, as cooler SST's and persistent shear have apparently taken their toll on this system.
After several small, short lived convective bursts in the SE and SW quads the past 12 hours or so, it appears that Cosme is waning as I write this, about 1am HST.
However, I wouldn't shut the book quite yet, as the next few days might be interesting.
From the latest (11pm HST) advisory package from the CPHC:
"COSME IS STILL SHOWING SIGNS OF LIFE ...
OVER THE PAST 6 HOURS AN AREA OF COLD CLOUDS ON THE SOUTHEAST SIDE OF COSME HAS EXPANDED AND COVERED THE CENTER. THAT MADE IT MORE DIFFICULT TO PINPOINT THE CENTER ON CONVENTIONAL INFRARED IMAGERY...BUT MICROWAVE IMAGERY SHOWED THE CENTER NICELY ... THERE WAS ALSO A NICE QUIKSCAT PASS (WHICH) SHOWED 30 KT WINDS EXTENDING AS MUCH AS 90 NM NORTHWEST OF THE CENTER."
But since this advisory, convection has again waned, but it may yet again flare and pulse during the overnight hours (Hawaii time) during the diurnal convective max cycle.
And if we do get a good burst near and over the LLC that persists, in spite of the shear, then central pressure may again drop and an upgrade might be in the works.
"WHILE THE TRACK HAS BEEN VERY CONSISTENT...FORECASTING THE INTENSITY REMAINS MORE UNCERTAIN. COSME CONTINUES TO MOVE OVER FAIRLY COOL WATER...ABOUT 77 DEGREES FAHRENHEIT...BUT THE SYSTEM HAS SHOWN SIGNS OF INTENSIFICATION ... WE KEPT THE INITIAL INTENSITY UNCHANGED AT 30 KT...
BUT IF THE CONVECTION NEAR THE CENTER PERSISTS OVER THE NEXT SIX HOURS IT IS *LIKELY* WE WOULD TAKE COSME BACK UP TO TROPICAL STORM INTENSITY ON THE NEXT BULLETIN."
But it's really touch-and-go and much depends on the ability of the convection to sustain itself and the system as a whole.
"COSME SHOULD REMAIN OVER RELATIVELY COOL WATER WITH FAIRLY LOW SHEAR OVER THE NEXT 48 HOURS...SO IF THE SYSTEM DOES LOSE ALL IT/S CONVECTION DURING THAT PERIOD...IT MAY WELL BECOME TOO WEAK TO HAVE MUCH CHANCE TO RE-INTENSIFY."
And on the flip side of the coin:
"IF COSME MANAGES TO KEEP SOME CONVECTION (AS IT MOVES WEST) ...IT WILL START MOVING BACK OVER WARMER WATER. IF SHEAR REMAINS WEAK ENOUGH AT THAT POINT...COSME MIGHT WELL RE-INTENSIFY."
It's hard to predict exactly what will happen to Cosme in the next day or two, hence:
"THESE UNCERTAINTIES KEEP OUR CONFIDENCE IN THE INTENSITY FORECAST RATHER LOW."
Looks like it could go either way. I wouldn't be too suprised to see it fizzle altogether, as it's happened so often in the past. But I've also seen a few depressions (and even remnants) flare up and regenerate as they approach warmer waters near the Islands.
(IMAGE OF COSMES' PROJECTED PATH TOWARDS AND JUST SOUTH OF THE HAWAIIAN ISLANDS)
http://www.prh.noaa.gov/cphc/tc_graphics/2007/sat/EP062007_070719_1100_sat.gif
And finally, a word from the good folks at the NWS forecast office in Honolulu, in their latest synoptic discussion (seperate from the official CPHC advisory discussion above) ...
"THE REEMERGENCE OF DEEP CONVECTION WITHIN TROPICAL DEPRESSION COSME NEEDS TO BE OF CONCERN TO THOSE WHO ARE MONITORING ITS PROGRESS. IF THESE THUNDERSTORMS PERSIST...COSME MAY HAVE A CHANCE TO REINTENSIFY LATER TONIGHT OR THURSDAY.
REGARDLESS OF ITS CURRENT OR FORECAST INTENSITY...ALL RESIDENTS IN THE STATE OF HAWAII NEED TO CLOSELY FOLLOW FUTURE ADVISORIES ON COSME.
EVEN IF THIS TROPICAL SYSTEM PASSES BY THE ISLANDS AS A WEAK LOW...THE PRESSURE GRADIENT BETWEEN THIS LOW AND HIGH PRESSURE TO THE NORTH WILL BE CAPABLE OF INCREASING WINDS TO SPEEDS NEAR OR ABOVE THE WIND ADVISORY THRESHOLD OVER LAND. THESE WINDS COULD BE ESPECIALLY STRONG OVER SOME OF THE HIGHER TERRAIN ON THE BIG ISLAND...AND POSSIBLY ON MAUI.  (Orographically enhanced winds, something Floridians never have to think about!)
FLOOD WATCHES MAY ALSO BE REQUIRED FOR PARTS OF THE STATE AS THE MOISTURE PLUME FROM COSME MOVES UP FROM THE TROPICS."
Hmmm..... Just a quick check of the IR loop before submitting this post reveals a new flare-up of strong thunderstorms in a tight, band-like formation on the WEST side of the LLC. Have a look and follow along with the convective trends, as they will make or break the future of Cosme.
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
Sorry to be making such lengthy posts, but there does seem to be increasing interest in Cosme as she approaches the Islands. Hope they've been interesting and informative.
PS: Thanks for your replies. It's great to get others' perspectives on the situation, as well. Keep 'em coming!
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Well, things are getting more interesting by the hour!
Despite still being over cooler SST's and in spite of the persistent moderate easterly shear, Cosme certainly appears to be attempting regeneration back to a tropical storm. And it's now quite likely she may just pull it off sooner or later in the next day or two.
Judging from the appearance of satellite imagery loops over the past few hours, I'd say she's well on her way to doing just that. After waning somewhat overnight, since this afternoon, Hawaii time, convective trends are again on the upswing.
http://weather.hawaii.edu/satellite/sata...amp;overlay=off
From the CPHC's latest (5pm HST) forecast discussion, highly paraphrased:
"THE INTENSITY FORECAST REMAINS LESS THAN CERTAIN. CONVECTION CONTINUES TO FLAIR UP MAINLY WEST OF THE CENTER. COSME REMAINS OVER FAIRLY COOL WATER OF ABOUT 77 DEGREES FAHRENHEIT.
THE LATEST AND SHIP FORECASTS CONTINUE TO INDICATE SOME SLIGHT STRENGTHENING BACK TO A MINIMAL TROPICAL STORM WITH SHIPS INDICATING 40 KT AT 48 HOURS AND 45 KT OUT AT 120 HOURS. THE HWRF GUIDANCE BRINGS COSME UP TO 37 KT IN 36 HOURS AND 47 KT OUT AT 48 HOURS.
THE UW-CIMSS EXPERIMENTAL VERTICAL SHEAR TC INTENSITY TREND ESTIMATES SHOW LESS SHEAR OVER THE SYSTEM THAN 6 HOURS AGO AND INDICATED FAVORABLE CONDITIONS FOR POSSIBLE INTENSIFICATION THROUGH 18 HOURS ... WE EXPECT COSME TO BE MOVING OVER WARMER WATER BUT ALSO INTO AN AREA WITH STRONGER VERTICAL SHEAR FROM A UPPER TROUGH NORTHWEST OF THE MAIN HAWAIIAN ISLANDS.
IT IS HARD TO SAY WHICH OF THESE FACTORS WILL PREVAIL. CONFIDENCE IN THE INTENSITY FORECAST REMAINS LOW."
And since this advisory, convection has continued to increase as the shear relaxes just a tad, per UW-CIMSS, and not just in the western semi-circle, but now is beginning to pop up in the NE quad, as well, though not especially deep quite yet.
Please view the provided attachment (above) for a good Microwave Imager Overpass, depicting the convection just to the west of the LLC, and a nice, well defined rainband forming in the NW quadrant and deep convection beginning to build in the NE quad, which seems to suggest that the shear is starting to relax a little, as just mentioned.
And the overall appearance of the depression steadily continues to improve, as well. Earlier this afternoon, it appeared somewhat elongated SW to NE, but now appears more symetrical and an extensive mid-level cloud shield is developing over the system, as well.
Shifting gears to a more local perspective:
NWS forecast office in Honolulu has recently issued a Flash Flood Watch for the Big Island of Hawaii, as well as a Wind Advisory for the upper slopes and summits of the tall mountains on the Big Island and Maui. Please view:
http://www.prh.noaa.gov/hnl/
... for color coded links to these special weather statements, (may include other statements by the time you read this).
It appears that the Big Island may pick up as much as 5 to 10 inches, possibly leading to localized flash flooding in some areas.
And the current wind advisory may need to be upgraded to a High Wind Warning for the higher slopes of the volcanoes, especially if Cosme does strengthen back to tropical storm force as she passes near the Islands.
For a nice close-up short IR loop of a Hawaii centered image please view:
http://www.prh.noaa.gov/hnl/satellite/Hawaii_IR_loop.gif
... as you see Cosme entering the theatre stage right.
Finally, (whew!) a snip from the latest NWS synoptic discussion (seperate from the CPHC's advisory/discussion) paints a very wet picture for the weekend:
"THE STRONG POSSIBILITY OF SIGNIFICANT RAINFALL FOR MAINLY WINDWARD PARTS OF THE THE BIG ISLAND HAS NECESSITATED ISSUANCE OF A FLASH FLOOD WATCH FOR THE BIG ISLAND TO COVER THE FRIDAY NIGHT AND SATURDAY TIME PERIOD. THE OTHER ISLANDS WILL RECEIVE LESS RAINFALL WITH A CHANCE OF SOME HEAVY SHOWERS.
PRESENTLY THE AMOUNT OF MOISTURE ACCOMPANYING THE TROPICAL SYSTEM APPEARS TO COVER A RELATIVELY LARGE AREA NORTH OF THE CENTER."
For a complete read of Hawaii's synoptic discussion, link to:
http://www.prh.noaa.gov/data/HFO/AFDHFO
... which may be different and further expanded by the time you read this.
So, all in all, it's quite likely that Cosme may pull a few more tricks out of her magicians' hat before all is said and done. And the media is likely to pick up on all this soon, too, like the Weather Channel and CNN, etc. and may even send reporters out to the Islands to do some live broadcasts, especially if Cosme *does* regenerate into a tropical storm.
The best part is that the Big Island, and the other Islands to a lesser extent, may get the good soaking it needs, ala Barrys' good quenching of Florida!
More later. Keep those replies coming!
Warm Aloha from Honolulu - Norm
|
CoconutCandy
User
Reged:
Posts: 245
Loc: Beautiful Honolulu Hawaii
|
|
Greeting All; I was away over the weekend, and decided not to make any posts.
Just thought I'd share a few closing thoughts on TD Cosme.
Well, Friday and Saturday were rather interesting, especially for the Big Island.
As the depression slipped south of the Islands on nearly a due west heading, the extensive moisture field on the north side of Cosme collided with the massive SE slopes of the Mauna Loa and Maune Kea volcanoes, and was orographically lifted, resulting in an extensive rain event, which they *really* needed!
Regeneration, as likely as it might have appeared due to the presence of tenacious convection, as well as most of the intensity model guidance on Friday, never quite materialized.
The easterly shear, which had knocked in down from Hurricane strength a few days earlier, was replaced by increasing SW shear from an upper-level low ( as sooooo... often happens! ) west of the Islands polished it off over the weekend.
But, as mentioned, numerous thunderstorms formed over most sections of the Big Island, and although there were a few flood advisories, no significant flash flooding occurred.
So! The Big Island gets a good drenching, really helping out agricultural interests, and those folks who get their water from water-catchment systems.
The Best of Both Worlds: No storm and lots of rain !! Wish it always worked out like that.
Hurricanes stay away! The Islands are just perfect without you. Let's hope for a quiet season in the Central Pacific. In the event another system does threaten, I will do my best to keep you all informed as to developments. And any interesting EastPac systems, as well.
Thanks for all the reads of my rather long posts and for your replies, too. It's been fun!
Now returning you to your regular scheduled programming: The Atlantic Basin.
Aloha Greetings from Honolulu - Norm 
--------------------
"Don't Get Stuck on Stupid" - General Honore, following Hurricane Katrina
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
