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Posted: (September 06, 2008 07:11 am)
| IMPACT OF HANNA TODAY/TONIGHT | ||||||
| CITY | LAST GFS | GFS NOW | LAST NAM | NAM NOW | MY CALL | CONDITIONS/WIND/IMPACT |
| RALEIGH NC | 1.02" | 1.44" | 2.92" | 3.62" | 2.47" | 2.50" RECORDED RAIN SO FAR |
| WILMINGTON NC | 1.58" | 1.54" | .50" | 1.74" | 1.83" | 1.79" RECORDED RAIN SO FAR |
| CAPE HATTERAS NC | 1.00" | .58" | .63" | .54" | .56" | TROPICAL STRM WINDS, SOME RAIN |
| RICHMOND VA | 1.70" | 1.56" | 2.95" | 2.35" | 2.00" | WINDS TO 40 MPH, SQUALLS |
| WASHINGTON DC | 3.03" | 4.41" | 5.88" | 3.11" | 3.97" | FLOODING N&W OF CITY |
| BALTIMORE MD | 2.71" | 3.98" | 6.37" | 3.44" | 3.87" | FLOODING N&W OF CITY |
| VIRGINIA BCH VA | 1.24" | .55" | 1.24" | .67" | .62" | TROPICAL STRM WINDS, SOME RAIN |
| OCEAN CITY MD | 1.26" | 1.00" | 1.05" | 1.23" | 1.11" | TROPICAL STRM WINDS, SOME RAIN |
| REHOBOTH BCH DE | 1.18" | 1.23" | 1.08" | 1.36" | 1.30" | TROPICAL STRM WINDS, SOME RAIN |
| DOVER DELAWARE | 1.49" | 1.77" | 1.12" | 2.70" | 2.16" | 40MPH WINDS, SQUALLS |
| PHILADELPHIA PA | 3.73" | 3.15" | 2.82" | 3.18" | 3.16" | FLOODING N&W OF CITY |
| MILLVILLE NJ | 2.12" | 1.70" | .99" | 2.77" | 2.22" | WINDY WITH SQUALLS, RAIN |
| ATLANTIC CITY NJ | 2.48" | 1.41" | .92" | 2.62" | 1.56" | TROPICAL STRM WINDS, SOME RAIN |
| TRENTON NJ | 3.61" | 3.30" | 2.43" | 3.17" | 3.21" | SQUALLS, HEAVY RAIN |
| BINGHAMTON NY | .25" | .25" | .42" | .70" | .43" | OCC. SHOWERS |
| SCRANTON PA | 1.51" | 2.21" | 4.51" | 2.86" | 2.43" | HVY RAIN IN SPOTS, SOME FLOODING |
| READING PA | 2.98" | 4.65" | 6.53" | 3.38" | 4.32" | FLOODING LIKELY |
| ALLENTOWN PA | 2.57" | 4.19" | 7.20" | 3.85" | 4.00" | FLOODING LIKELY |
| LANCASTER PA | .67" | .20" | 1.11" | XXXX | .34" | SQUALLS, SHOWERS |
| SEASIDE HEIGHTS NJ | 1.98" | 2.89" | 1.29" | 2.87" | 2.88" | TROPICAL STRM WINDS, SOME RAIN |
| NEW YORK CITY | 2.11" | 4.81" | 2.02" | 4.29" | 4.56" | FLOODING LIKELY N & W OF CITY |
| WESTERN LONG ISL | 2.58" | 2.98" | 1.88" | 4.05" | 3.85" | FLOODING NASSAU COUNTY |
| EASTERN LONG ISL | 3.19" | 2.20" | 1.78" | 4.06" | 3.58" | FLOODING POSSIBLE |
| NEWARK NJ | 2.37" | 4.51" | 2.18" | 3.94" | 4.31" | FLOODING LIKELY |
| OVERALL MINOR IMPACT | MODEL CHANGES BELOW…… | |||||
| OVERALL MODERATE IMPACT | NAM SHOWS DECREASE | |||||
| OVERALL HIGH IMPACT | NYC/ALLENTOWN/READING PA FLOODING | |||||
| FLOODING MINOR | GFS CAUGHT UP TO NAM | |||||
| FLOODING MODERATE | OVERALL N & W OF MAJOR | |||||
| FLOODING HIGH | CITIES WILL HAVE FLOOD PROBLEMS | |||||
MODEL CHANGES.....
If you have read my blogs on the flooding issues the last few days you know I was leaning toward the NAM on the flood potential, esp. N & W of the big cities. The NAM dropped off a bit on the big totals in Reading PA and Allentown PA, but the GFS made a comeback from the low numbers on the last few runs. This tends to happen with these two models. The NAM gets out of the gate quickly on rain and snow and the GFS slowly finds it way to the NAM adjusted numbers 24 hours before a storm.
BIG RAIN REAL FAST....
The problem later today in Baltimore, Washington Metro and tonight in Philly metro is the rate the rain comes down. Take a look at your city above, most of that total comes in a 6 hour period not the entire day. That is a real FLASH FLOOD problem for many areas, esp. hilly areas north and west of the major cities. Yes this storm will pick up in forward motion but at the same time it will get squeezed out of some pretty good moisture.
Reading and Allentown will see 3.62" of rain in 6 hours !!! That is my real concern later today and tonight.
Baltimore/DC Metro will see 3.00" of rain in 4-6 hours this afternoon, that is a problem.
NYC Metro will see 3-4" of rain in 6-9 hours later tonight with places over 5". Spread those amounts over a day and you get some problems, do in 6 hours and you have FLASH FLOODING !
MODELS DO NOT SEE STORMS AND LIFT THAT WELL
Yes I do think the NAM has better grids when it comes to topography, but models often miss micro meteorology and embedded storms with tropical systems. What this means is look at models as a big 3D box. The data put into that box is divided by grids or cubes. The NAM does a better job of this and those grids do keep in mind the topography but only to a certain degree. Models do not see those storms in the tropical system and that can pop a few places in the 8-10" rainfall range overall with Hanna. This was the case with Floyd, lolipops of rain over 12". Now this is different than Floyd but we will get a good dose of rain today and tonight for the I-95 area.
MY THINKING ON THE RAIN TODAY...........IMPORTANT READ...........
IF you are N & W of the Washington DC/Baltimore/NYC/Philly metro areas you need to watch this very carefully today and tonight. If your basement floods, move the stuff now not later because this will come down quick and hard ! Some may say hey you are overplaying this but I'll tell you I'd rather be safe than sorry. If your hometown does not flood, and I hope it does now, think of this as a drill for the next tropical systems lined up in the Atlantic and Gulf. Best of luck to all today and check back. IF YOU HAVE FLOODING SEND US THE INFO IN THIS BLOG. IF YOU HAVE WIND/RAIN NUMBERS SEND US THE INFO Look at the numbers for Wilmington NC and Raleigh NC. The rainfall today has already passed what both models predicted, that is often a sign of things to come as this storm heads north.
