Effects of Tropical Storm Hanna...

By: Zachary Labe , 8:15 PM GMT on September 05, 2008

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Tropical Storm Hanna...

Satellite Picture...

(Courtesy of Penn State EWall)

First Thoughts...
For me tropical season always brings lots of headaches, but yet the thrill of excitement when a storm heads my direction. It has been a pretty long time since a significant tropical storm has moved my direction. The last major storm I remember was Hurricane Isabel which headed up the coast bringing winds gusting over 60mph here in Harrisburg. So now, September 2008, we have Hanna headed our way. This blog is a different format than usuall due to the fact that a tropical system has not impacted our area this year. By the time Hanna reaches our area it will maintain tropical storm force with winds sustained near 50mph near the center of circulation. But Hanna has a very large circulation which will spread strong wind gusts widespread over the region. Hanna will also cause some very heavy rain as tropical moisture overspreads the region with high PWAT anomalies. Some areas may recieve up to 8inches of rain across southeastern Pennsylvania. The ground is very dry and this may cause flash flooding as the ground will not be immediantly ready to suck in the rainfall. I will talk all about the immediant impacts on the region in the sections below.

Track of Hanna...

(Courtesy of NOAA)

Current Advisories...

(Courtesy of NOAA)

Hanna's Impacts...
Rainfall- The largest impact on the state of Pennsylvania from Hanna will most likely be rainfall. A narrow band of very high anomaly PWATs is streaming northward across the eastern half of Pennsylvania. Hanna has had a very subtropical look to it with most of the moisture confined to the western half of the circulation. A very large precipitation shield of light to moderate rain will overspread the region ahead of the circulation overnight late tonight and early tomorrow morning. The center of circulation will lift northward across the region with a large moisture shield to the west of the circulation. The center of Hanna I believe will track just to the east of the I-95 corridor. As the rain shield becomes heavier, rain rates may approach very high rates near 2inches per hour. Tropical moisture for a relatively unknown reason does not show up on doppler radar very well. It seems the radar has less DBZs than what really should be indicated. Rainfall amounts are going to exceed 3inches in many locations. There will be a sharp cutoff to the heavier precipitation and I think that will eye up just to the east of the central Pennsylvania line. Rainfall will be heaviest along the southeast piedmont region with isolated rainfall amounts nearing 9inches. But Hanna will be moving at a very fast pace so amounts more than that are not overally likely. Conditions have been very dry over the region lately and the ground has almost become like cement. Heavy tropical downpours will not be immediantly able to sponge into the ground, so they will rapidly run into urban areas and streams causing areas of flash flooding. River flooding is not likely due to recent low water levels. Rainfall should beginning to subside across the region by 8-9pm Saturday evening. Most all areas east of the Susquehanna River will see rainfall amounts over 1-2inches. Here is my rainfall map...


Wind- Wind will more of an impact than originally thought to be several days ago. It appears as if the center of circulation will travel up through North Carolina up through eastern Virginia then up through the Delmarva. The tropical storm force wind shield will be pretty large with winds sustained over tropical storm force wind as far west as the Lehigh Valley. Areas to the west of the Lehigh Valley but east of the Susquehanna River will still see tropical storm force wind gusts, but not likely to see sustained winds over 39mph. Winds will gust up to near 60-65mph across far eastern Pennsylvania. Winds of this magnitude are capable of downing trees and powerlines. This evening I would suggest making sure all objects are strapped down so they do not get blow around. The area with the highest threat of wind is around the Philadelphia metro area. Currently they are under an inland tropical storm force wind warning. Elsewhere areas may see winds gust up to 50mph. Here is my current wind map...


Storm Surge- Pennsylvania off course does not have any ocean coastlines, but for those with concerns off the Chesapeake it appears there will be a 2-3ft water rise. The highest water level rises will occur around midday Saturday as the circulation of Hanna approaches the bay region during coastal high tides. Here is a list of coastal high tides along the Chesapeake Bay...
HAVRE DE GRACE...2:42 PM SATURDAY
BOWLEY BAR...12:22 PM
FORT MCHENRY...11:31 AM
FELLS POINT...11:40 AM
ANNAPOLIS...9:53 AM
CHESAPEAKE BEACH...8:39 AM
SOLOMONS ISLAND...6:46 AM

"Radar for Central Pennsylvania"


"Radar for Eastern Pennsylvania"


Severe Weather- I am not looking at too much of a severe weather threat with Hanna. Areas to the east of the center of circulation will be under the highest threat for severe weather. As with any landfalling tropical system, tornadoes are always a threat. Here is the latest from the SPC...
...ERN SEABOARD...
03Z OFFICIAL NHC FCST PLACES THE CENTER OF TC HANNA OVER THE SE CSTL
PLAINS OF NC AT 12Z...SRN NJ AT 00Z/07 AND THEN ACCELERATES IT NEWD
INTO THE GULF OF MAINE BY 12Z/07 AS AN EXTRATROPICAL CYCLONE. DEEP
MOIST ADIABATIC PROFILES AND 0-1KM SRH OF 300+ M2/S2 ALONG/E OF THE
TRACK OF THE CENTER WILL MAINTAIN THE THREAT OF BRIEF TORNADOES/
WATERSPOUTS THROUGH THE PD.

Current Surface Map...

(Courtesy of Penn State EWall)

Current Weather Map...
Looking at the current weather map we have a cold front moving quite slowly across eastern parts of Ohio. Much of Gustav's moisture with the front has fizzled out, so I am not expect much precipitation for western Pennsylvania. A southern low-level jet will nose its way in across Pennsylvania making for some strong winds aloft. A deep trough is currently moving through the Midwest with very dry upper and mid levels. A high pressure across the Atlantic is departing that area and moving east. This all is the perfect setup for a tropical storm to come up the coast and ride around along the trough.

Current Water Vapor Loop...

(Courtesy of Penn State EWall)

Computer model forecasts...
Looking at the computer models I am going with the 12z HWRF track. I believe this model has a great track record this tropical season and I believe it has a good hold on the forecast with Hanna. Looking at other models the NAM has the storm slightly farther west than other models, but the NAM has been not intiating the actual National Hurricane Center location for Hanna, so for right now I am throwing away the NAM. The GFS is a little farther east with this system. I think the GFS is just to far east in the track. Here is the 12z HWRF close up over Pennsylvania...


Final Thoughts...
It should definitely be an exciting day on Saturday for many areas across the Middle Atlantic. Winds will gust over tropical storm force at times and we will all get a very nice beneficial rain which still could cause chaos with areas of flooding. I will be on most of Saturday to relay reports from my area. I checked my weather station and it looks all set. This forecast above was relatively short based on other forecasts I have made before, but I really did not want to make it too detailed for this event. This blog still is under construction through the weekend as changes come about. I look foward to hearing observations from across the region on Saturday. We are ready for you Hanna! Prepare for the worst, but hope for the best. Have a wonderful day!!!

Forecast Model Links
-NAM model 12z...Link
-GFS model 12z...Link
-NMM model 12z...Link
-SREF model 9z...Link

Severe Weather Links
-Atmospheric Soundings Skewt T charts...Link
-SPC Mesoscale Analysis Pages...Link
-Public Spotter Reports for State College NWS...Link
-Severe Weather Model Forecast indices...Link
-Severe Weather Parameter Definitions...Link

Flooding Links
-Automated Pennsylvania Rainfall Recording Stations...Link
-Flash Flooding Guidance...Link
-HPC Forecasts for Excessive Rainfall...Link
-Hydrology Predictions for Lakes, Rivers, and Streams...Link

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Viewing: 162 - 112

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162. MDFirefighter
1:34 PM GMT on September 07, 2008
Check my blog for a few pictures of the flooding that Hanna caused
Member Since: February 11, 2006 Posts: 1 Comments: 1201
161. Zachary Labe
1:12 PM GMT on September 07, 2008
JDinWPA- That is chilly! But we can expect that here in September. You will probably get some rain with the frontal passage on Tuesday.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
160. JDinWPA
1:09 PM GMT on September 07, 2008
Good morning Bliz. Another cool night, down to 49. We haven't had any rain since Fay, Aug. 27 - 29. Might be working on a record for this year! lol. Have a good day.
159. Zachary Labe
12:57 PM GMT on September 07, 2008
cchamp6- Wow that is a lot of rain. Any flooding issues up that way?

jthal57- Pretty amazing about the tornado. No warning at all. NWS will probably get a good yelling at.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
158. jthal57
12:10 PM GMT on September 07, 2008
Blizzard and CChamp: There was an unconfirmed tornado in east Allentown yesterday, based on eyewitness accounts. They will check it out and confirm today. I'll let you know.
My blog has the story link if you're interested.
157. cchamp6
11:00 AM GMT on September 07, 2008
Rainfall total for event is 5.32" ( gauge was off line for about 30 minutes during heavy rain) Wind gust recorded was 27 mph at 11:37 last evening.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
156. cchamp6
1:56 AM GMT on September 07, 2008
I am off to bed at 10 pm. Rain is still pouring down with a total of 4.75" so far!! The end is in sight, hopefully.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
155. Zachary Labe
1:29 AM GMT on September 07, 2008
***New blog coming tomorrow morning in the form of a typical weekly weather format.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
154. Zachary Labe
12:44 AM GMT on September 07, 2008
TheRasberryPatch- Thanks. And thanks for your storm reports today. Yea it is still a little gusty around the Bay region as the center continues to march to the northeast.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
153. TheRasberryPatch
12:29 AM GMT on September 07, 2008
nice job with the forecast and the blog, Blizz.
still showing strong winds on the eastern shore of delmarva
Member Since: January 26, 2007 Posts: 72 Comments: 6233
152. Zachary Labe
12:26 AM GMT on September 07, 2008
cchamp6- You will probably go over that prediction based on radar trends and current observations.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
151. cchamp6
12:22 AM GMT on September 07, 2008
No I do not. It is working ok now. I went out in the deluge to temporarily secure it. Stupid me. 3.58" and still going. I fully expect the 4.29" that Sully predicted.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
150. Zachary Labe
12:20 AM GMT on September 07, 2008
cchamp6- I was shocked to hear the report when you mentioned it. No warning what-so-ever for Allentown. Mt. Holly is going to get in trouble for this. Again thanks for pointing it out when you heard it on TWC. That stinks with your weather station. Do you have any other outdoor guage to at least see your final total?
Member Since: December 14, 2007 Posts: 278 Comments: 15045
149. cchamp6
12:18 AM GMT on September 07, 2008
No kidding on the tornado for PA. I knew what I heard and was surprised when you guys couldnt verify it.

The wind has picked up here. KNocked my rain gauge off. Suddenly it stopped showing rainfall when it was still pouring. I need to fasten that thing down better I guess.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
148. Zachary Labe
12:15 AM GMT on September 07, 2008
***Well tropical storm Hanna is moving out of the state of Pennsylvania. Rainfall amounts were generally over 1inch east of central Pennsylvania with very high amounts in the Lehigh Valley, Southeast Piedmont, and eastern Lower Susquehanna Valley. I think my rainfall forecast was pretty accurate, I think I should have included York County in the 1inch+ zone, though. Now the only part of the forecast that did not pan out was the winds. Now areas in extreme southeastern Pennsylvania did see an occasional 40mph gust, but nothing more than that in Pennsylvania. Overall I consider me forecast to be pretty accurate with the main fault being the forecast winds.

I want to thank everyone who posted in the blog today for making this a great blog! There were lots of observations and people's opinions about making forecasts. Again thanks to all of you today!!!
Member Since: December 14, 2007 Posts: 278 Comments: 15045
147. Zachary Labe
12:09 AM GMT on September 07, 2008
JDinWPA- Thanks for checking in!

cchamp6- Well turns out The Weather Channel was correct today. Good spot and thanks for the report or else I would have completed missed the report! Anyway a tornado possibly touched down in Allentown. Link to local news headline... Link.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
146. JDinWPA
12:06 AM GMT on September 07, 2008
Hi Bliz. I pretty sure we didn't even get a drop of rain, but it was occasionally close. The front moved through this afternoon, cool and windy. It started clearing off here around 7 so it shouldn't be too long before it get to you. The wind has quit, the moon is out... looking like a much better night than the day was!
145. Zachary Labe
11:57 PM GMT on September 06, 2008
cchamp6- I heard a report of nearly 4inches of rain near Westport, CT.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
144. cchamp6
11:53 PM GMT on September 06, 2008
Link for my radar. Its not stopping anytime soon. Link
Member Since: December 21, 2006 Posts: 5 Comments: 1637
143. cchamp6
11:52 PM GMT on September 06, 2008
Up to 5" for my area. Sully said 4.29" ! I think he may nail that one.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
142. Zachary Labe
11:51 PM GMT on September 06, 2008
cchamp6- Wow, how much rain were you locals calling for?
Member Since: December 14, 2007 Posts: 278 Comments: 15045
141. cchamp6
11:48 PM GMT on September 06, 2008
Just went over the 3" mark.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
140. Zachary Labe
11:47 PM GMT on September 06, 2008
cchamp6- Wow, becareful up there!
Member Since: December 14, 2007 Posts: 278 Comments: 15045
139. cchamp6
11:43 PM GMT on September 06, 2008
Getting breezy. Tornado warning for the county just to my south.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
138. Zachary Labe
11:38 PM GMT on September 06, 2008
TheRasberryPatch- Similar conditions here. Sort of an spooky night with the clouds moving extremely fast and a slight northernly breeze.

cchamp6- Wow that is some crazy rain up your way. Any wind?
Member Since: December 14, 2007 Posts: 278 Comments: 15045
137. cchamp6
11:04 PM GMT on September 06, 2008
Up to 2.61".
Member Since: December 21, 2006 Posts: 5 Comments: 1637
136. TheRasberryPatch
10:58 PM GMT on September 06, 2008
rain has stopped and the clouds are breaking.
2.37" of rain for the storm. most we have had here in a good while
barometer got to a low 29.59", but now it is starting to rise
winds are non-existant
Member Since: January 26, 2007 Posts: 72 Comments: 6233
135. cchamp6
10:51 PM GMT on September 06, 2008
2.07" and raining like mad. Thunder and lightning as well.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
134. Zachary Labe
10:41 PM GMT on September 06, 2008
weathergeek5- Good evening!!! I have never seen a special weather statement like that before.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
133. weathergeek5
10:39 PM GMT on September 06, 2008
Hey I am back had a long day at work, but I got totally soaked so Hanna got me.

Here are some weather statements for my area:

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
625 PM EDT SAT SEP 6 2008

DEZ001-MDZ008-NJZ009-010-012>020-026-027-PAZ067>071-070000-
BUCKS PA-CAMDEN NJ-CECIL MD-CHESTER PA-COASTAL OCEAN NJ-DELAWARE PA-
EASTERN MONMOUTH NJ-GLOUCESTER NJ-HUNTERDON NJ-MERCER NJ-MIDDLESEX NJ-
MONTGOMERY PA-NEW CASTLE DE-NORTHWESTERN BURLINGTON NJ-OCEAN NJ-
PHILADELPHIA PA-SALEM NJ-SOMERSET NJ-SOUTHEASTERN BURLINGTON NJ-
WESTERN MONMOUTH NJ-
625 PM EDT SAT SEP 6 2008

...HANNA EXITING THE REGION BUT CAUSING SIGNIFICANT LOW LEVEL
SHEARING TO PRODUCE POSSIBLE TORNADOES...

AT 619 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF ROTATING SHOWERS SPINNING AROUND THE CENTER OF TROPICAL
STORM HANNA. AT 5 PM...THE CENTER OF HANNA WAS LOCATED OVER
SOUTHWEST SUSSEX COUNTY DELAWARE. NORTH OF HANNA...THE SHOWERS WERE
ROTATING COUNTERCLOCKWISE AND THE INTERACTION WITH THE LAND IS
CAUSING SIGNIFICANT LOW LEVEL CONVERGENCE AND SHEAR TO PRODUCE
ROTATING SHOWERS THAT COULD PRODUCE SHORT LIVED VORTEX CENTERS OR
FUNNEL CLOUDS.

THESE ARE SHORT LIVED EVENTS AND IN SOME CASES VERY DIFFICULT TO
LOCATE ON RADAR. IF YOU SEE ANY SUSPICIOUS CLOUDS TAKE SHELTER
IMMEDIATELY.

well this nextTHE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* FLOOD WARNING FOR
THE CHRISTINA RIVER AT COOCHS BRIDGE.
* FOR THIS EVENING...OR UNTIL THE WARNING IS CANCELLED.
* AT 5:54 PM SATURDAY THE STAGE WAS 9.5 FEET.
* MINOR FLOODING IS FORECAST.
* FLOOD STAGE IS 10.5 FEET.
* FORECAST...RISE ABOVE FLOOD STAGE THIS EVENING AND CREST SLIGHTLY
ABOVE FLOOD STAGE.
* IMPACT...AT 10.0 FEET...FLOODING BEGINS IN THE TOWN OF CHRISTIANA.

one always happens:



FORECASTER:EBERWINE

Member Since: December 25, 2005 Posts: 0 Comments: 1743
132. Zachary Labe
10:37 PM GMT on September 06, 2008
TheRasberryPatch- Rain has ended here.

cchamp6- It was dark here too several times as the tropical rain bands moved over the region.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
131. cchamp6
10:01 PM GMT on September 06, 2008
Its dark like night now. That cant be good.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
130. cchamp6
9:56 PM GMT on September 06, 2008
First batch of rain has put down nearly an inch in less than an hour.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
129. TheRasberryPatch
9:25 PM GMT on September 06, 2008
rain still coming down. i have 2.34" of rain for the storm.
winds are still slight averaging 4 mph
barometer is 29.59" and falling
Member Since: January 26, 2007 Posts: 72 Comments: 6233
128. Zachary Labe
9:19 PM GMT on September 06, 2008
09/06/2008 0345 PM

Quarryville, Lancaster County.

Heavy rain e3.00 inch, reported by Emergency Mngr.

Three inches of rain were reported along with several
trees and branches down. Ponding of water on several
roadways was also reported. Ema indicated that these
conditions were County wide.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
127. Zachary Labe
9:14 PM GMT on September 06, 2008
cchamp6- Lol, I guess so. Looks like rain is moving into Connecticut. I guess you are in for a long night with wind and rain.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
126. cchamp6
9:11 PM GMT on September 06, 2008
I guess that is a good thing that TWC passed on bad information.

No tornado and no damage.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
125. Zachary Labe
9:00 PM GMT on September 06, 2008
carolinagal- Thanks for stopping by!
Member Since: December 14, 2007 Posts: 278 Comments: 15045
124. carolinagal
8:54 PM GMT on September 06, 2008
Hope all is well there. Looks like you've felt more of Hanna than I did. Take care.
Member Since: July 15, 2005 Posts: 156 Comments: 6774
123. Zachary Labe
8:48 PM GMT on September 06, 2008
Here northeast of Harrisburg...

Heavy rain
69degrees
4mph sustained wind, 17mph gust
.29inch rainrate
1.29inches of rain so far
Member Since: December 14, 2007 Posts: 278 Comments: 15045
122. Zachary Labe
8:31 PM GMT on September 06, 2008
Quoting cchamp6:
They said there was damage.

I just heard from a storm spotter out in Allentown that TWC man corrected himself and said there was wind damage in Allentown, which even that I find hard to believe. So far I cannot find any tornado confirmation. The spotter reports that have not even had any thunder all day. I tell you that weather channel always seems to be making mistakes.

MDFirefighter- Similiar conditions here.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
121. MDFirefighter
8:23 PM GMT on September 06, 2008
Raining heavily. Winds have been steady around 15-20. Streets are flooding
Member Since: February 11, 2006 Posts: 1 Comments: 1201
120. cchamp6
8:21 PM GMT on September 06, 2008
They said there was damage.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
119. Zachary Labe
8:19 PM GMT on September 06, 2008
jthal57- That surely is some much needed rain for your area.

TheRasberryPatch- Seems like everything is going pretty close to forecast.
Member Since: December 14, 2007 Posts: 278 Comments: 15045
118. TheRasberryPatch
8:17 PM GMT on September 06, 2008
rain so far for the storm is 2.03"
wind is slight. 10 min avg. is 3mph
Member Since: January 26, 2007 Posts: 72 Comments: 6233
117. jthal57
8:16 PM GMT on September 06, 2008
Quoting cchamp6:
TWC reported a tornado touchdown in Allentown.

in PA???
116. Zachary Labe
8:16 PM GMT on September 06, 2008
cchamp6- O my, lets hope that storm report turns out false. I did not hear that.

MDFirefighter- So how are things going down there?
Member Since: December 14, 2007 Posts: 278 Comments: 15045
115. jthal57
8:15 PM GMT on September 06, 2008
Latest stats here in Northampton County:

Temp. 73
Dew: 69
Bar. 29.74 falling
Rain in last hour: .75"
total rain today: 1.10"
highest rainfall rate: 1.81"/hr.
114. MDFirefighter
8:14 PM GMT on September 06, 2008
I'm back
Member Since: February 11, 2006 Posts: 1 Comments: 1201
113. cchamp6
8:12 PM GMT on September 06, 2008
TWC reported a tornado touchdown in Allentown.
Member Since: December 21, 2006 Posts: 5 Comments: 1637
112. Zachary Labe
8:11 PM GMT on September 06, 2008
cchamp6- Lol, well that sure is an exact estimate. I just went outside and winds gusting now to 15-20mph with heavy rain.
Member Since: December 14, 2007 Posts: 278 Comments: 15045

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About Blizzard92

Cornell University- Atmospheric Sciences Student; Central PA SKYWARN Storm Spotter; American Meteorological Society Member; PA CoCoRaHS Branch Member

Personal Weather Stations

Linglestown, PA
Elevation: 520 ft
Temperature: 24.2 °F
Dew Point: 15.2 °F
Humidity: 68%
Wind: Calm
Wind Gust: 9.0 mph
Updated: 10:37 AM EST on January 18, 2014

About Personal Weather Stations