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Zeta appears to be strengthening

Updated at end of post.
Original post from 2:54pm:
Last night forecaster Avila at the National Hurricane Center forecasted Tropical Storm Zeta to weaken. However, he noted that this was also the case with Epsilon not too long ago when Epsilon continued to strengthen. Looking at model data yesterday showed the cold upper-level air temperature to be the only factor contributing towards strengthening. Well, in the tradition of Vince and Epsilon before it, Tropical Storm Zeta appears much healthier. This was my forecast last night since with storms like this, I have given up on science. The GFDL model went along with this forecast before and seems to be back on board with a hurricane in 1-3 days.

0:NHC forecast track

These were Avila's words last night:

THIS IS LIKE PREVIOUS TROPICAL CYCLONE EPSILON ALL OVER AGAIN. MOST OF THE CONVENTIONAL GUIDANCE SUGGESTED THAT ZETA SHOULD HAVE BEEN DISSIPATED BY NOW...WELL IT IS NOT INDEED...AND ZETA IS PRETTY MUCH ALIVE AT THIS TIME. TO THE SHIPS MODEL WHICH DISSIPATES ZETA BY 48 HOURS...THE COOLER THAN NORMAL 200 MB TEMPERATURE IS THE ONLY PARAMETER CONTRIBUTING TO THE MAINTENANCE OF THE CYCLONE. ON THE OTHER HAND...THE GFDL INSISTS ON MAKING ZETA A HURRICANE IN A COUPLE OF DAYS AND IT IS HARD TO GO AGAINST IT. HOWEVER...WITH STRONG WESTERLIES ALOFT AND DRY AIR HEADING FOR ZETA...I HAVE NO CHOICE BUT TO FORECAST WEAKENING AGAIN AND AGAIN.

It looks like Avila is a man who is learning to use caution after Tropical Storm Epsilon. Unfortunately forecaster Pasch is on duty at NHC today and these were his words:

VISIBLE SATELLITE IMAGES SHOW THAT ZETA'S CENTER IS BECOMING EXPOSED JUST TO THE SOUTHWEST OF THE DEEP CONVECTION. DVORAK INTENSITY ESTIMATES SUGGEST THAT THE STORM HAS WEAKENED...HOWEVER A QUIKSCAT PASS FROM A FEW HOURS AGO SHOWED 35-40 KT WINDS JUST OUTSIDE OF THE CONVECTION. IT IS ASSUMED THAT HIGHER SPEEDS WERE OCCURRING IN THE HEAVIER SHOWERS...SO THE INTENSITY IS HELD AT 45 KT FOR THIS ADVISORY. ANALYSES FROM THE UNIVERSITY OF WISCONSIN CIMSS SHOW AN AREA OF INCREASING VERTICAL SHEAR ASSOCIATED WITH A WELL-DEFINED UPPER-LEVEL TROUGH ABOUT 10 DEGREES TO THE WEST OF THE TROPICAL CYCLONE. THIS ADDITIONAL BLAST OF WESTERLIES SHOULD CAUSE WEAKENING...AND THE OFFICIAL FORECAST ANTICIPATES THAT ZETA WILL BE DISSIPATING WITHIN ABOUT 36 HOURS.

I have no idea what tropical storm he is looking at, but it doesn't seem to be Zeta (at least by my eyes). Here is a look at the infrared satellite imagery from last night:

1:Yesterday's satellite

Now check out today's:

2:Today's satellite

Weakening? Where? Zeta looks much better organized today and I am tempted to jump on board with the GFDL and call for Zeta to become a January hurricane.

3:GFDL forecast

*NOTE* The National Hurricane Center's graphics and text archive does not seem to be working. It seems as if their programmers never expected a January system and their archives are not listing any advisories after the New Year.

Update at 4:16pm
Forecaster Pasch at NHC has begun to admit he needs to take a lesson from Avila. So far there is no white flag to be seen, but I am keeping a close watch.

ALTHOUGH A WEAKENING TREND SEEMED IMMINENT EARLIER TODAY...AS THE LOW-CLOUD CENTER STARTED TO BECOME EXPOSED...A NEW BURST OF DEEP CONVECTION SUBSEQUENTLY REFORMED NEAR THE CENTER. ZETA HAS THUS FAR REFUSED TO WEAKEN IN...WHAT APPEARS TO BE...A STRONGLY SHEARED ENVIRONMENT. CLEARLY WE NEED AN INCREASED UNDERSTANDING OF INTENSITY CHANGE FOR SYSTEMS IN THE SUBTROPICS SUCH AS ZETA...EPSILON...VINCE...ETC. NOTWITHSTANDING... GLOBAL MODEL FORECASTS INDICATE EVEN STRONGER UPPER-LEVEL FLOW OVER THE STORM WITHIN 1-2 DAYS AND IT IS HARD TO CONCEIVE THAT A TROPICAL CYCLONE WILL BE ABLE TO SURVIVE FOR VERY LONG IN SUCH A HOSTILE DYNAMICAL ENVIRONMENT. THEREFORE I HAVE NOT BACKED OFF ON THE FORECAST OF WEAKENING. OF COURSE...ZETA MAY HAVE OTHER IDEAS.

Sometimes:
I <3 global warming.


Posted by Bryan Woods | Permalink