Collection of Hurricane Irene Map Posts
**********************************************************************

On 24 August, 2011 17:04:13 GMT Jared Klein wrote:

Hi Dave, Mike and Lance,

I bet you guys are excited for the potential heavy rainfall associated with Irene
in New England? The latest track of Irene looks prime for coastal front setup
over New England (see attached figure labeled 06ZGFS_low-level_thetae_frontog_pwat.png 
and two corresponding 6-hr precip images). There will be a nice wrap-around low-level jet 
advecting high theta-e air (upper 340s/lower 350) into a tightening frontal boundary 
(forecasted frontogenesis values are large). While the GFS is picking up on this, I think 
(due to the 'coarse' 0.5 degree resolution), the mesoscale band of enhanced rain will be much 
tighter than what it shows.

To add fuel to the fire (or a fire hose to the flooding), there could be a potential for an 
AT or just LOT PRE late Friday night into Saturday over southern New England and/or NYC region? 
It looks like downstream ridging from the TC could interact with the approaching trough over 
Ontario/Quebec to enhance the jet streak over central/northern New England (see two images labeled PRE). 
Since the models typically handle the diabatic component of the downstream ridge building poorly, 
the upper jet streak could be stronger and develop sooner than what the models are depicting. 
During this time the plume of high PWAT moisture from the TC intersects a low-level boundary. 
Interestingly, the 06Z GFS and 12Z NAM (which is just coming in as I type this) both don't 
have any indication of a PRE at this time. Also note, by 12Z Saturday the TC is located about 
1000 km (which is the mean PRE-TC separation distance shown by Cote 2007) SSW of the potential 
PRE location at this time.

Any thoughts on the setup for heavy rainfall associated with a PRE followed 
by a coastal front with the approach of Irene?

Hope everyone is doing well.
Jared

**********************************************************************

On 27 August, 2011 20:05:23 GMT, Bosart, Lance F wrote:

Hi Everyone,

Fri map discussion resumed early this semester in response to interest in TC Irene, hoopla, hype, hysteria and all.

Motivated by the excellent track forecasts (at least by the global models) 
and the so-so intensity forecasts for TC Irene, the bulk of the freewheeling 
discussion was devoted to TC science and forecasting issues. In particular, discussion 
focused on these questions:  

1. What governs TC size vs. intensity? 
2. What determines the vertical profile of wind speed in a TC as a function of time? 
3. What controls how rapidly and to what extent oceanic heat fluxes are exported to the atmosphere?
4. What governs the time-dependent structure of the planetary boundary layer within the TC circulation?
5. What new observations are needed to help answer these questions?
6. What needs to be done to improve TC intensity forecasting (and how should intensity be defined)?
7. What should be done to improve how we communicate TC threats to the general public?

Distilling the discussion down to a few key (and possibly contentious) points.........

Looking at the TC Irene track forecasts from assorted deterministic and ensemble forecasts 
for the last few days shows that the global models are generally superior to the limited area 
models prompting the question as to why are we devoting so many resources to limited area models when, 
arguably, we might be better off redirecting some of these resources towards increasing the number of 
ensemble members in global models and advancing probabilistic track forecasting?

Looking at the TC Irene intensity forecasts from assorted deterministic and ensemble forecasts for the 
last few days shows that the majority of model forecasts (especially the limited area models) over deepened 
Irene based on forecast minimum central pressures under 925 hPa vs. observed minimum central pressures near 
940 hPa, prompting the question as to what extent our inability to specify the time-dependent oceanic heat 
content, wind, temperature, and moisture distribution properly within the TC circulation is adversely impacting 
our ability to forecast tropical cyclone intensity (based on central pressure) and intensity change properly?

While awaiting the availability of more comprehensive data, it appears that standard NHC methods designed to 
estimate surface wind speeds based on flight level aircraft observations and remotely sensed observations yielded 
surface wind speeds in Irene that were too high by 10-20 kt, prompting the question as to what physical processes 
govern the time-dependent vertical profile of wind speeds in a TC and what was the source for the apparent wind speed 
overestimates in Irene?

The majority of ensemble weather forecasting members are generated through initial condition uncertainty 
prompting the question as to what extent increasing the number of ensemble members that are generated 
through uncertainty associated with planetary boundary layer structure, oceanic heat content, and model 
physics might yield more realistic and reliable PDFs for TC intensity and intensity change forecasts?

Does the Cat 5 hype and hysteria for a Cat 2 and Cat 1 storm, and the associated apparent indifference 
of many members of the general public toward a "ho-hum" Cat 1 storm, provide additional evidence that the 
time has come to move beyond that Saffir-Simpson Cat 1-5 rating scale to convey the true threat of a TC 
(e.g., the size and slow motion of Irene will offset, at least in part is "lowly" and misleading Cat 1 
status along the East Coast)? Do we need to move toward creating a new scale that will consider metrics 
like storm size and storm duration to get at an areal (integral under the curve) measure of intensity 
and potential impact based on some parameter like the accumulated cyclone energy (ACE)? I suspect that 
the general public would quickly learn to relate to a metric like "ACE." I suspect that the media would 
love to introduce the NHC Director as "the man or woman from ACE" with the latest and greatest forecast 
to the general public. And, with tongue planted firmly in cheek, who knows, perhaps Ace Hardware would 
contribute millions of dollars toward TC research for all of the free publicity an ACE TC intensity 
scale might yield.

Map discussion concluded with a low-tech rainfall guessing contest (see attached picture) whereby 
everyone made a guess of the total Irene storm rainfall that would be measured at my house. The mean 
total rainfall forecast was 6.26 inches based on guesses made at 2100 UTC 26 Aug 2011 (and kudos to 
Jay Cordeira for using mm!). 

Awaiting the onset of rain and wondering how widespread and prolonged power outages will be 
once 30-50 kt wind gusts start toppling trees residing in quasi-saturated soils (before the rain) 
and and/or large tree branches onto power lines. External members of map can help out us locals by 
posting interesting data and images, given the relatively high probability that many of us will 
lose our internet connections. Thanks in advance for the help.

Lance