A Forensic Meteorological Perspective on the American Revolutionary War

Battles of Trenton and Princetonby

Gerald Mulvey, CCM #571

(Trenton)Northrop Grumman Corporation

andElliot Abrams, CCM #340

(Princeton)AccuWeather

January 21, 2008,

Updated Sep 17, 2009Trenton Princeton

Introduction

• Battle of Trenton Overview• Supporting Data• Synoptic Situation• General Snowfall &

Temperature Trends• Weather in the Battle Theater• Battlefield Temperature• Meteorological Impacts• The Official Report

Trenton Princeton• Battle of Princeton Overview• Battlefield Location• Clark House• Battlefield Paintings• Princeton Battlefield• Supporting Data• Battlefield Reports• Thomas Jefferson’s Weather

Records• Battlefield Temperature• Battle field Reports

Historical Significance

What if ……References & Acknowledgements

Historical Significance

• Series of defeats of the revolutionary army

• Enlistment ends January 1, 1776

• Position of the British forces

• Washington’s goals

• Strategic importance of Trenton and Princeton

Trenton Princeton

Battle of Trenton OverviewTrenton

Location

Force SummaryAmerican: Gen. Washington: 2,400 troops, 18 pieces of artillery – McConkey’s FerryBrig. Gen. Ewing: 700 troops – Trenton FerryCol. Cadwalader: 1,800 troops, 2 pieces of artillery – Dunk’s FerryBritish (Hessian): Col. Rall: 1,400 troops, 6 pieces of artillery

Date & Time12/25/1776 ~4:00 PM to 12/16/1776 ~9:30 AM

Courtesy of the University of Texas Libraries, The University of Texas at Austinhttp://www.lib.utexas.edu/maps/histus.html#military.html

Trenton

Supporting Data(Trenton, NJ)

• Sunset 12/25/1776: 4:39 PM Sunrise 12/26/1776: 7:21 AM• Moonrise 12/25/1776: 5:31 PM Moonset 12/26/1776: 8:36 AM Moon phase 12/25/1776 waning gibbous 12/26/1776 waning gibbous

99% of visible disk illuminated 97% of visible disk illuminated • Tide Predictions at Trenton Falls, Trenton, New Jersey

December, 1776

• Ground condition - Frozen• Delaware River river ice conditions near Trenton

Trenton

Synoptic SituationTrenton Princeto

n

HHHH

HH

12/25/1776Strong high pressure cell over western New York weakens during the day. Low pressure off the Carolinas rapidly intensifies during the late night hours.12/26/1776Rapidly moving intensifying Low tracks NE off shore through the day. Low positioned off the Massachusetts coast moves ENE by the end of the day.12/27/1776High pressure re-established over NE U.S.

LL

LLLL

Avg. winter Gulf Stream location

12:00 LT 12/25/1776 24:00 LT 12/25/1776 12:00 LT 12/26/1776

LL

24:00 LT 12/26/1776

General Snowfall & Temperature Trends

0

10

20

30

40

50

60

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 2 4 6 8 10

Temperature: Philadelphia 2W, 1776 -1777

December January

Trenton

1 – Trappe, PA: 12 "2 – Pennroyal, VA: 24 "3 – Monticello, VA: 22-24"4 – Salem, NC: 3-4"5 – Friedberg, NC: 12+"

24"

12"

Snowfall Observations

12/25 – 27/1776

oF

8 AM3 PM

Trenton

Battle of Trenton

***

Weather in the Battle Theater

Weather estimates were interpolated in time and estimated to current descriptions.

Trenton

12/25/1776 12/26/1776

16:00 18:00 20:00 22:00 24:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00

Storm Intensity: Initial onset 21:00 to 22:00 12/25First renewal 4:00 12/26Final surge 7:30 to 8:00 12/26

x x x, ,,,, ***

**

**

** *

.***

.*** *

March to the Delaware begins Crossing begins Washington crosses Crossing complete

March to Trenton starts Battle begins Hessians surrender Withdrawal starts Troops across to Pennsylvania

Battle Temperature• March to the Delaware starts

• Crossing the Delaware begins

• Crossing completed for main battle group

• March to Trenton begins

• Forces arrive at Trenton & the battle is opened

• Hessians surrender

• Withdrawal starts

• Delaware re-crossing starts

Trenton

10

15

20

25

30

35

40

8:00

12:0

0

16:0

0

20:0

0

0:00

4:00

8:00

12:0

0

16:0

0

20:0

0

0:00

Time

De

g (

F)

12/25 12/26

Meteorological Impacts

• Troop mobility: river crossing and land• Artillery movement: river crossing and land• Observables: visibility & noise • Defensive operations: pickets, patrols & sentries• Offensive operations: munitions, artillery

targeting• Anticipated behavior: Hessians & Americans

The Official ReportTrenton

Battle of Princeton OverviewPrinceton

Location

Force SummaryAmerican: Gen. Washington: 4,600 troops, 18 pieces of artillery – British Gen Cornwallis: 1,200 Troops 6 pieces of Artillery

Date1/3/1777

Princeton

The Clark House. Wounded officers from both sides were treated here. General Hugh Mercer, mortally wounded by seven bayonet stabs, died here nine days after the Battle of Princeton.

Mercer County New Jersey is named for him.

Princeton

Battlefield Paintings: on display at the Edge of the Princeton Battlefield

Princeton

Barren trees stand silent sentinel at the edge of the Princeton Battlefield as dusk closes in on a wintry evening 18 days short of 231 years after the event.

Princeton

Princeton

A

B

Exhibit A: This is an example of how news was relayed. The reports may have been reliable, but they were typically at least second hand and hearsay by the time they reached historians

Exhibit B: Indicates low (< 20 degrees) lunar declination around this time. Not shown: a lunar eclipse had occurred two weeks earlier

Princeton

George Washington’s letter to the Continental Congress. Reference to moving baggage to Burlington “soon after dark” (Jan 2, 1777) suggests the formerly muddy roads were already starting to freeze. Was the march timed to take advantage of some moonlight? Moonrise was at 1:20 AM (though only 33% of the lunar face was lit).

Princeton

When did the march actually begin? Here, one of the participants, Captain Thomas Rodney of Delaware, mentions a time that was two hours later than the one written by George Washington.

Princeton

Princeton

Comparison: Jan1 1996- Dec 31, 2008…56.1 degrees F

Thomas Jefferson’s Weather RecordsMonticello, VA

December 1776

January 1777

Trenton Princeton

On Jan. 1, temperature remained in the low 40s here but soared to 51 degrees F in Philadelphia. This suggests the low pressure area that caused rain at Princeton the night of January 1 had a warm front that moved along and near the coastal plain but whose warm sector did not reach inland to Mt. Vernon because of cold air damming. Adding support to damming: soldiers encountered snow still on the ground from earlier storms when they reached northwest New Jersey on Jan 6, 1777.

Princeton

Based on records by Phineas Pemberton, 2 miles west of Philadelphia

Wind Dir. NW

Sgt R____ as reported in Pennsylvania Magazine of History, XX (1896):

“The horses attached to our cannon were without shoes, and when passing over the ice, they would slide in every direction and could advance only by the assistance of our soldiers. Our men, too, were without shoes or other comfortable clothing; and as traces of our march toward Princeton, the ground was literally marked with the blood of the soldiers’ feet.”

From Rebels and Redcoats: a scene from the Princeton battlefield.

“At one moment, thirty yards from the enemy, he (George Washington) sat astride his white horse at the head of his troops, such a vulnerable target that young John Fitzgerald, his aide, covered his face, because he could not bear to see the general fall. But, enveloped by smoke, the General escaped harm.”

The dawn had been frosty, and near the center of a high pressure area, the wind was weak. A near surface inversion likely prevented the vertical dispersion of smoke, and the light winds allowed it to remain concentrated on the battlefield. At the same scene on the day before post-frontal northwest winds would have cleared the smoke more rapidly, making such behavior much more risky.

Princeton

General Washington originally wanted to march to (New) Brunswick ahead of Cornwallis. Much equipment and approximately $2 million dollars was being stored there, and a victory might have caused the English government to abandon their war effort. This is speculation.

Princeton

General Washington explains his move to Morristown, NJ after the Battle of Princeton

Princeton

General Washington explains efforts to keep ahead of the British, who were trying to race northeastward from Trenton after having been fooled the night before.

Princeton

In a period of 10 days, the Revolution had gone from repulsed to revitalized. In two stunning victories, General Washington brought new respect to the American effort. Washington came to realize that it was not necessary to fight his better equipped foe head on. Instead, he needed to keep his forces in play long enough to frustrate the British fighters and erode support for this expensive war back in England.

If the Christmas night storm had not occurred, the Hessians might have been more alert to the possibility of attack.If the Delaware had been choked with ice at Washington’s Crossing, the forces could not have crossed the river.If the snow and sleet had not been propelled by north winds behind a soon to depart East Coast storm, the Hessians would have been able to clearly see their attackers.If it had not rained the night of January 1, Cornwallis’ forces would have made more progress toward Trenton and might have been able to rout the rebels before dark.If George Washington had not been weather savvy from his Virginia farming experience, he would not have recognized the opportunity presented by the rapid cooling on the afternoon and evening of January 2.

Trenton Princeton

In England, a similar northwesterly flow would not have prompted such confidence in a nighttime freeze. The English soldiers were less likely to have recognized this factor and taken action to avoid its consequences.

If a near surface inversion and light winds had not been present to make the smoke remain over the battlefield at Princeton, General Washington might have been an easy target for the nearby British soldiers.

If Washington had not recognized the likelihood of a thaw on the afternoon of January 3, 1777, he would not have moved so quickly to put distance between his northbound army and Cornwallis’ angry pursuit following the Battle of Princeton.

Trenton Princeton

ReferencesAmbrose, K., D. Henry and A. Weiss, (2002): Washington Weather: The Weather Sourcebook for the D.C. Area,

Historical Enterprise, VA Chadwick, B, (2005): George Washington’s War, Sourcebooks, Inc., Naperville, ILDwyer, W. (1983): The Day is Ours! November 1776 - January 1777: An Inside View of the Battles of Trenton and

Princeton, Rutgers University Press, New Brunswick, NJ Freeman, D., (1968): Washington, Simon & Schuster, NYFisher, D., (2004): Washington’s Crossing, Oxford University Press, NYGyory, J., A. Mariano, and E. Ryan: The Gulf Stream: Ocean Surface Currents

http://oceancurrents.rsmas.miami.edu/atlantic/gulf-stream.htmlKetchum, R.,(1973): The Winter Soldiers, Henry Holt & Company, NYKocin, P. and L. Uccellini (2004): Northeast Snowstorms, vol. 1, American Meteorological Society, Boston, MA Ludlum, D., (1966): Early American Winters 1604 – 1820, American Meteorological Society, Boston, MA Ludlum, D., (1998): The Weather of Independence, Weatherwise, Nov/Dec, Heldref PublicationsMcCullough, D (2005): 1776, Simon and Schuster, NYSavas, T and J. Dameron, (2006): A Guide to the Battles of the American Revolution, Savas Beatie, New York, NY Scheer, G, and Rankin, H.J. (1957): Rebels and Redcoats, Da Capo Press, Chapel Hill, NCSolomon, S., J. Daniel, and D. Druckenbrod, (2007): Revolutionary Minds, American Scientist, vol. 96, no. 5, pp. 430-

437  Stryker, W., (1898): The Battles of Trenton and Princeton, The Riverside Press, NJ (reprinted 2001, The Old Barracks

Association, NJ) Symond, C., (1986): A Battlefield Atlas of the American Revolution, The Nautical & Aviation Publishing Company of

America, Mount Pleasant, SC Winters, H. G. Galloway, W. Reynolds and D. Rhyne, (1998): Battling the Elements: Weather and Terrain in the

Conduct of War, Johns Hopkins University Press, Baltimore, MDWood, W., (1990): Battles of the Revolutionary War 1775-1781, Da Capo Press, Chapel Hill, NC 

Acknowledgements:The authors would like thank Todd Ehret at NOAA, National Ocean Service Center for Operational Oceanographic Products and Services, Tide

and Tidal Current Predictions, for calculating the tidal timing and heights for the battle of Trenton. They would like also to thank Eric Johnson at the Jefferson Library, Monticello, for research on the observations of Thomas Jefferson.

Notes:Astronomical data was provided by the U.S. Naval Observatory, Washington D.C

Title page flag images are from the FOTW Flags Of The World website at http://flagspot.net/flags

Trenton Princeton