91L … new strong Tropical Wave in South Tropical Atlantic

Posted by wxrisk | GENERAL,HURRICANE SEASON 2012 | Saturday 30 July 2011 5:35 pm

1230 EDT 30 JULY

the midday satellite pictures look even more impressive. One can clearly see 2 THICK bands of convection on the images.  All the oz aand midday models show a pretty serious trough moving off the East coast AUG 4-5. If that is correct then this potential tropical storm or hurricane will be kicked out to sea.

2100 EDT   JULY  28

More importantly is that the  satellite  images are showing a really significant looking tropical wave which has developed off the  ITCZ– the into tropical conversion zone.  Very strong tropical wave has a clear closed low level circulation   and a  surface Low of 1010 MB … and it it   way out there at  around  30-35  degrees  west  Longitide.




Posted by wxrisk | GENERAL,HURRICANE SEASON 2012 | Thursday 28 July 2011 10:50 pm

1650  EDT   JULY 29

Don  looks a little better    this  afternoon.   Nothing  great but   it is clearly   STILL a    TD– tropical depression or bare minimal tropical storm.   Its clear that  DON will not  make it to   Minimal category   1   Hurricane  before landfall .



1000  EDT  JULY  28

DON  looks  lile  crap this morning.  NHC says that it has several centers and none of them had become the dominant one and whenever   that is the case you always have a row the weak  disorganized system.  It  is possible that Don might collapse over the next 6-10  hours…  But if it survives conditions should improve as it approaches the Southern Texas Coast.

1730   EDT   JULY   27



The recon   found a  really   strong  system…  mean sea level pressure  (MSLP)   of 1006 MB and  Max  flight  winds   45 knots  with  Gust to  57 knots.   I dont  know for certain that  NHC will  upgrade this  system  directly to  Tropical  storm  status  at  5pm… but they  should.  Especially given that  this baby  is only  60-72  hours away  from landfall… and the    Hurricane  models  are increasing   this system to  strong   TS   threshold…. and   a few  Hurricane  models  show a  borderline   Min Cate 1   cane at  impact.

The  Forecast  has NOT  changed. The     SEVERE biased  GFDL   model should  be ignored  because that Model has a  strong  NORTH or Poleward  Bias. The   SYNOPTIC  situation  clearly shows  that  there is little chance of   Tropical storm DON  making  landfall   above  Galveston Bay/ Houston.    The  GFS and GFDL  models  once again show the  WEAKEST       ” dome”  over the southest states of any of the   Models  and  because   they  do…  DON  turns    to the NW  much  sooner… and hence an impact   at Galveston Bay.






1400 PM   EDT  JULY 27

 Tropical  Disturbance  90L is  now RAPIDLY   developing … that much  is  clear from the  Midday  IR and  VIS`  satellite  picture.  There is a  pool  of 90 degree F  sea surface temps  in the   Yucatan Channel  that is  also   having some sort of impact.  The recon is  on its  way  and   I would  be stunned if  they did  NOT  find a   Tropical  Depression   later on today.





1900  EDT   JULY  26

We finally have a significant tropical system to focus on here at the end of July.  This system has been  designated  90L by the tropical prediction center (NHC).  As you can see from the satellite pictures this is a fairly well organized system which have developed significantly in last 24 HRS has moved into the western and northwestern portions of the Caribbean Sea.

This feature has the potential to develop into a tropical storm and I suppose IF…  if there were to rapidly develop over the next 36 hours it might even make hurricane strength but the odds of strongly against   that happening.  Some of the hurricane model intensity forecast do show in approaching the borderline threshold… which  you can see  here. 

The forecast itself with regard to this potential tropical cyclone is interesting and it shows why one must take a look of the overall pattern as opposed to  JUST  using hurricane models.  Here is the latest forecast package regarding the hurricane models– the 18z JULY 26.  As you can see most of the models are taking this system into far southern Texas and that area certainly could use the rain!!

Interestingly for most of the past 90 days there   has been a monster dome in the jet stream centered over Texas and Oklahoma.  This dome of course is one reasons why they have had such an extreme drought over that portion of the nation and  the drought has been sustaining the dome itself so the two features —  the dome and the drought– are locked in some sort of bizarre symbiotic relationship .

The point here is that for the first portion of summer and  probably for most of the 2ND  hald of the Summer and  Autumn the drought and the dome over Texas and Oklahoma is going to prevent most of the tropical cyclone activity in the Gulf of Mexico from hitting Texas.  Anything that moves thru the Western Gulf of Mexico will probably be deflected by this huge dome and be forced to turn its west southwest or even southwest into northern or Central Mexico south of Brownsville.  But at this particular time the pattern has the dome breaking down. 

Over the next few days the dome was going to redevelop over the southeast states –which will cause our region to turn quite hot for three of four days.  But more importantly if tropical disturbance  90L   were to to develop it sets up a pathway for the  90L to follow the dome’s  SW periphery and turn WNW  into the Gulf of Mexico and perhaps make a landfall of north of Brownsville TX.     We can see how this might develop by taking a look of the GFS model at 500 MB  at  36  hrs and  72  hrs and 96  hrs. 

In addition over the past 24 hours MSLP  have fallen significantly over the Northern Gulf of Mexico.

Longer term the over all atmosphere across the equatorial regions and the subtropical regions are about to move into a much more favorable pattern.  This image from CPC  shows 200 MB  Vertical Velocities. 

 Without getting too technical the  BROWN areas shows   “sinking air“   and conditions which are hostile to tropical cyclone development  …  while the GREEN  areas show rising motion which enhances the potential of any tropical disturbance into becoming a tropical cyclone.  In this image the features move from left to right so as you can see right now over the Gulf of Mexico the Caribbean and the tropical Atlantic  is in  BROWN areas  or the sinking year.   But as you can see… coming in from the Pacific and even as far west as China …there is a large expanse of area rising motion which is represented by the GREEN  regions.  Over the next week this energy will begin to move into the Gulf of Mexico and Western Caribbean and then rapidly spread into the entire tropical Atlantic region at the same time as the counter moves into August. 

Do not be surprised if we see a significant burst of activity in the tropical Atlantic during the first two weeks of August.  La cities


Posted by wxrisk | GENERAL,SEASONAL FORECASTS | Wednesday 20 July 2011 8:07 pm

20 JULY    1800 EDT

We are reaching a turning point in the overall  Summer 2011  pattern.     There have there been some significant changes over the last few weeks which are increasing the threat for a substantially hotter and drier second half of the  Summer 2011 then what my original Summer forecast  predicted.   But this is more than just my forecast:   it also means that the official Summer forecast from the CPC   (climate prediction center)   as well as most other private forecast services   — all of which  forecasted a  cooler and   wet  Summer  over the Midwest –  are also going to be in trouble .

My job as a grain and energy meteorologist is not to continue to insist that my forecast might end up  verifying after all …. as  if there is some sort of  meteorological  miracle  that MIGHT happen.  If  I am going to be wrong    then  my job is to see where I am wrong …figure out what’s happening …and to tell you with the correct or updated forecast.   In other words my job is not to blow smoke of my own ASS.
So for the  Summer it has been a rather  cool Summer for much of the upper Plains and the Midwest.  For example Des  Moines Iowa  through   JUNLY  13   has seen   8  days  with a Max temperature above  90°…  Chicago has had 9 days with a Max temperature above 90….°Indianapolis 11 days…  And Lincoln Nebraska 13 days.  Given that it is now almost the midpoint of the Summer   –July 15 –    it is safe to say that   so far we have NOT seen  a lot of heat and if things don’t change soon this lack of heat is going to cause real problems with respect to  GDD.


This was  the  KEY premise   of  my forecast for the Summer of 2011 has to do with   SOIL  MOSITURE  snd excessively   wet   areas  over the Upper Plains and  all of Midwest  that  developed and  INCREASE  in MARXCH APRIL and MAY 2011. 
Essentially my contention was that the large areas of very wet or super saturated ground conditions over the upper Plains and the Midwest was going to restrict or become very resistant to any sort of sustained heat dome or heat ridge pattern developing over the Midwest.     This link will take you back to the Summer 2011 forecast…   so you may READ it in detail
These next couple of images show the RAINFALL  RELATIVE TO NORMAL  for the month of MAY and for the month of JUNE  2011.  As you can see MAY 2011  as a very wet month across most of the central and upper Plains and the Midwest with large areas seeing anywhere from 200 to 500% above normal rainfall.

The month of JUNE 2011 was not quite as wet but there was still large areas of  wet conditions over portions of the Dakotas and the WCB into Central Illinois.

These images supported of my contention that  as  long as the Summer of 2011   saw   saturated  or  super saturated  ground conditions …it  was going to be very difficult to get sustained heat into the Upper Plains and the Midwest and therefore we would have GDD problems.
So far so good.

However over the last two weeks there  has  been a significant change in the pattern which  has turned things dramatically drier.  During the July 4 weekend we had a short burst of  mpressive heat over portions of the Plains  and Midwest.  It only lasted two with three days but it effectively began to dry out the pattern.     This image shows the total rainfall relative to normal over the nation in the last 14 days since June 30.  As you can see things are dramatically drier across all of the upper plains and the Midwest with large areas seeing only 25 to 50% of normal rainfall over the last two weeks. 


This combined with seasonally warm temperatures has pulled a lot of moisture out of the ground and allow things to dry up.  At this point however we have not seen a lot of heat.
That is why this upcoming heat wave or heat interval from July 15/16  to July23/ 24 is going to be so important.  Not only will this heat dome bring a lot of impressive  heat  but more importantly it is  going to continue to pull a lot of moisture out of the ground and allow things to dry out even faster.  For some of the wet  areas in the upper Plains that  is  a bad thing and  they   certainly could use the heat.  But this heat dome which is coming up for next week has longer term implications.

This up coming   Heat Dome  means that the soils will continue to dry out and by the time we get to the end of JULY the maps showing rainfall anomalies will be even MORE  Below Normal  than they are now.     This much drier ground over large areas of the Plains  and the Midwest will set the stage for August and the potential for more significant heat ridge  /  Heat domes   to come north from the drought areas of the lower Plains into the heart of the Midwest.  That  is what is really important   about    this upcoming heat dome.  It  is  going cause a lot of drying and a lot of crop stress   AND  also set the stage for more potential trouble for the late corn and beans in August over both the eastern and western corn belt areas.